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freebsd/sys/kern/sched_ule.c
Attilio Rao 435068aab7 Fix sched_switch_migrate(): 
- In 8.x and above the run-queue locks are nomore shared even in the
  HTT case, so remove the special case.
- The deadlock explained in the removed comment here is still possible
  even with different locks, with the contribution of tdq_lock_pair().
  An explanation is here:
  (hypotesis: a thread needs to migrate on another CPU, thread1 is doing
  sched_switch_migrate() and thread2 is the one handling the sched_switch()
  request or in other words, thread1 is the thread that needs to migrate
  and thread2 is a thread that is going to be preempted, most likely an
  idle thread. Also, 'old' is referred to the context (in terms of
  run-queue and CPU) thread1 is leaving and 'new' is referred to the
  context thread1 is going into.  Finally, thread3 is doing tdq_idletd()
  or sched_balance() and definitively doing tdq_lock_pair())

  * thread1 blocks its td_lock. Now td_lock is 'blocked'
  * thread1 drops its old runqueue lock
  * thread1 acquires the new runqueue lock
  * thread1 adds itself to the new runqueue and sends an IPI_PREEMPT
    through tdq_notify() to the new CPU
  * thread1 drops the new lock
  * thread3, scanning the runqueues, locks the old lock
  * thread2 received the IPI_PREEMPT and does thread_lock() with td_lock
    pointing to the new runqueue
  * thread3 wants to acquire the new runqueue lock, but it can't because
    it is held by thread2 so it spins
  * thread1 wants to acquire old lock, but as long as it is held by
    thread3 it can't
  * thread2 going further, at some point wants to switchin in thread1,
    but it will wait forever because thread1->td_lock is in blocked state

This deadlock has been manifested mostly on 7.x and reported several time
on mailing lists under the voice 'spinlock held too long'.
Many thanks to des@ for having worked hard on producing suitable textdumps
and Jeff for help on the comment wording.

Reviewed by:	jeff
Reported by:	des, others
Tested by:	des, Giovanni Trematerra
		<giovanni dot trematerra at gmail dot com>
		(STABLE_7 based version)
2009-09-15 16:56:17 +00:00

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/*-
* Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This file implements the ULE scheduler. ULE supports independent CPU
* run queues and fine grain locking. It has superior interactive
* performance under load even on uni-processor systems.
*
* etymology:
* ULE is the last three letters in schedule. It owes its name to a
* generic user created for a scheduling system by Paul Mikesell at
* Isilon Systems and a general lack of creativity on the part of the author.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_hwpmc_hooks.h"
#include "opt_kdtrace.h"
#include "opt_sched.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/turnstile.h>
#include <sys/umtx.h>
#include <sys/vmmeter.h>
#include <sys/cpuset.h>
#include <sys/sbuf.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
int dtrace_vtime_active;
dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
#endif
#include <machine/cpu.h>
#include <machine/smp.h>
#if defined(__sparc64__) || defined(__mips__)
#error "This architecture is not currently compatible with ULE"
#endif
#define KTR_ULE 0
#define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
#define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
#define TDQ_LOADNAME_LEN (PCPU_NAME_LEN + sizeof(" load"))
/*
* Thread scheduler specific section. All fields are protected
* by the thread lock.
*/
struct td_sched {
struct runq *ts_runq; /* Run-queue we're queued on. */
short ts_flags; /* TSF_* flags. */
u_char ts_cpu; /* CPU that we have affinity for. */
int ts_rltick; /* Real last tick, for affinity. */
int ts_slice; /* Ticks of slice remaining. */
u_int ts_slptime; /* Number of ticks we vol. slept */
u_int ts_runtime; /* Number of ticks we were running */
int ts_ltick; /* Last tick that we were running on */
int ts_ftick; /* First tick that we were running on */
int ts_ticks; /* Tick count */
#ifdef KTR
char ts_name[TS_NAME_LEN];
#endif
};
/* flags kept in ts_flags */
#define TSF_BOUND 0x0001 /* Thread can not migrate. */
#define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */
static struct td_sched td_sched0;
#define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
#define THREAD_CAN_SCHED(td, cpu) \
CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
/*
* Cpu percentage computation macros and defines.
*
* SCHED_TICK_SECS: Number of seconds to average the cpu usage across.
* SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across.
* SCHED_TICK_MAX: Maximum number of ticks before scaling back.
* SCHED_TICK_SHIFT: Shift factor to avoid rounding away results.
* SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count.
* SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks.
*/
#define SCHED_TICK_SECS 10
#define SCHED_TICK_TARG (hz * SCHED_TICK_SECS)
#define SCHED_TICK_MAX (SCHED_TICK_TARG + hz)
#define SCHED_TICK_SHIFT 10
#define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
#define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
/*
* These macros determine priorities for non-interactive threads. They are
* assigned a priority based on their recent cpu utilization as expressed
* by the ratio of ticks to the tick total. NHALF priorities at the start
* and end of the MIN to MAX timeshare range are only reachable with negative
* or positive nice respectively.
*
* PRI_RANGE: Priority range for utilization dependent priorities.
* PRI_NRESV: Number of nice values.
* PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total.
* PRI_NICE: Determines the part of the priority inherited from nice.
*/
#define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN)
#define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2)
#define SCHED_PRI_MIN (PRI_MIN_TIMESHARE + SCHED_PRI_NHALF)
#define SCHED_PRI_MAX (PRI_MAX_TIMESHARE - SCHED_PRI_NHALF)
#define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN)
#define SCHED_PRI_TICKS(ts) \
(SCHED_TICK_HZ((ts)) / \
(roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
#define SCHED_PRI_NICE(nice) (nice)
/*
* These determine the interactivity of a process. Interactivity differs from
* cpu utilization in that it expresses the voluntary time slept vs time ran
* while cpu utilization includes all time not running. This more accurately
* models the intent of the thread.
*
* SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
* before throttling back.
* SLP_RUN_FORK: Maximum slp+run time to inherit at fork time.
* INTERACT_MAX: Maximum interactivity value. Smaller is better.
* INTERACT_THRESH: Threshhold for placement on the current runq.
*/
#define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT)
#define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT)
#define SCHED_INTERACT_MAX (100)
#define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2)
#define SCHED_INTERACT_THRESH (30)
/*
* tickincr: Converts a stathz tick into a hz domain scaled by
* the shift factor. Without the shift the error rate
* due to rounding would be unacceptably high.
* realstathz: stathz is sometimes 0 and run off of hz.
* sched_slice: Runtime of each thread before rescheduling.
* preempt_thresh: Priority threshold for preemption and remote IPIs.
*/
static int sched_interact = SCHED_INTERACT_THRESH;
static int realstathz;
static int tickincr;
static int sched_slice = 1;
#ifdef PREEMPTION
#ifdef FULL_PREEMPTION
static int preempt_thresh = PRI_MAX_IDLE;
#else
static int preempt_thresh = PRI_MIN_KERN;
#endif
#else
static int preempt_thresh = 0;
#endif
static int static_boost = PRI_MIN_TIMESHARE;
static int sched_idlespins = 10000;
static int sched_idlespinthresh = 4;
/*
* tdq - per processor runqs and statistics. All fields are protected by the
* tdq_lock. The load and lowpri may be accessed without to avoid excess
* locking in sched_pickcpu();
*/
struct tdq {
/* Ordered to improve efficiency of cpu_search() and switch(). */
struct mtx tdq_lock; /* run queue lock. */
struct cpu_group *tdq_cg; /* Pointer to cpu topology. */
volatile int tdq_load; /* Aggregate load. */
int tdq_sysload; /* For loadavg, !ITHD load. */
int tdq_transferable; /* Transferable thread count. */
short tdq_switchcnt; /* Switches this tick. */
short tdq_oldswitchcnt; /* Switches last tick. */
u_char tdq_lowpri; /* Lowest priority thread. */
u_char tdq_ipipending; /* IPI pending. */
u_char tdq_idx; /* Current insert index. */
u_char tdq_ridx; /* Current removal index. */
struct runq tdq_realtime; /* real-time run queue. */
struct runq tdq_timeshare; /* timeshare run queue. */
struct runq tdq_idle; /* Queue of IDLE threads. */
char tdq_name[TDQ_NAME_LEN];
#ifdef KTR
char tdq_loadname[TDQ_LOADNAME_LEN];
#endif
} __aligned(64);
/* Idle thread states and config. */
#define TDQ_RUNNING 1
#define TDQ_IDLE 2
#ifdef SMP
struct cpu_group *cpu_top; /* CPU topology */
#define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
#define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
/*
* Run-time tunables.
*/
static int rebalance = 1;
static int balance_interval = 128; /* Default set in sched_initticks(). */
static int affinity;
static int steal_htt = 1;
static int steal_idle = 1;
static int steal_thresh = 2;
/*
* One thread queue per processor.
*/
static struct tdq tdq_cpu[MAXCPU];
static struct tdq *balance_tdq;
static int balance_ticks;
#define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)])
#define TDQ_CPU(x) (&tdq_cpu[(x)])
#define TDQ_ID(x) ((int)((x) - tdq_cpu))
#else /* !SMP */
static struct tdq tdq_cpu;
#define TDQ_ID(x) (0)
#define TDQ_SELF() (&tdq_cpu)
#define TDQ_CPU(x) (&tdq_cpu)
#endif
#define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type))
#define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t)))
#define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
#define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t)))
#define TDQ_LOCKPTR(t) (&(t)->tdq_lock)
static void sched_priority(struct thread *);
static void sched_thread_priority(struct thread *, u_char);
static int sched_interact_score(struct thread *);
static void sched_interact_update(struct thread *);
static void sched_interact_fork(struct thread *);
static void sched_pctcpu_update(struct td_sched *);
/* Operations on per processor queues */
static struct thread *tdq_choose(struct tdq *);
static void tdq_setup(struct tdq *);
static void tdq_load_add(struct tdq *, struct thread *);
static void tdq_load_rem(struct tdq *, struct thread *);
static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
static __inline void tdq_runq_rem(struct tdq *, struct thread *);
static inline int sched_shouldpreempt(int, int, int);
void tdq_print(int cpu);
static void runq_print(struct runq *rq);
static void tdq_add(struct tdq *, struct thread *, int);
#ifdef SMP
static int tdq_move(struct tdq *, struct tdq *);
static int tdq_idled(struct tdq *);
static void tdq_notify(struct tdq *, struct thread *);
static struct thread *tdq_steal(struct tdq *, int);
static struct thread *runq_steal(struct runq *, int);
static int sched_pickcpu(struct thread *, int);
static void sched_balance(void);
static int sched_balance_pair(struct tdq *, struct tdq *);
static inline struct tdq *sched_setcpu(struct thread *, int, int);
static inline struct mtx *thread_block_switch(struct thread *);
static inline void thread_unblock_switch(struct thread *, struct mtx *);
static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
struct cpu_group *cg, int indent);
#endif
static void sched_setup(void *dummy);
SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
static void sched_initticks(void *dummy);
SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
NULL);
/*
* Print the threads waiting on a run-queue.
*/
static void
runq_print(struct runq *rq)
{
struct rqhead *rqh;
struct thread *td;
int pri;
int j;
int i;
for (i = 0; i < RQB_LEN; i++) {
printf("\t\trunq bits %d 0x%zx\n",
i, rq->rq_status.rqb_bits[i]);
for (j = 0; j < RQB_BPW; j++)
if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
pri = j + (i << RQB_L2BPW);
rqh = &rq->rq_queues[pri];
TAILQ_FOREACH(td, rqh, td_runq) {
printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
td, td->td_name, td->td_priority,
td->td_rqindex, pri);
}
}
}
}
/*
* Print the status of a per-cpu thread queue. Should be a ddb show cmd.
*/
void
tdq_print(int cpu)
{
struct tdq *tdq;
tdq = TDQ_CPU(cpu);
printf("tdq %d:\n", TDQ_ID(tdq));
printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
printf("\tLock name: %s\n", tdq->tdq_name);
printf("\tload: %d\n", tdq->tdq_load);
printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
printf("\tload transferable: %d\n", tdq->tdq_transferable);
printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
printf("\trealtime runq:\n");
runq_print(&tdq->tdq_realtime);
printf("\ttimeshare runq:\n");
runq_print(&tdq->tdq_timeshare);
printf("\tidle runq:\n");
runq_print(&tdq->tdq_idle);
}
static inline int
sched_shouldpreempt(int pri, int cpri, int remote)
{
/*
* If the new priority is not better than the current priority there is
* nothing to do.
*/
if (pri >= cpri)
return (0);
/*
* Always preempt idle.
*/
if (cpri >= PRI_MIN_IDLE)
return (1);
/*
* If preemption is disabled don't preempt others.
*/
if (preempt_thresh == 0)
return (0);
/*
* Preempt if we exceed the threshold.
*/
if (pri <= preempt_thresh)
return (1);
/*
* If we're realtime or better and there is timeshare or worse running
* preempt only remote processors.
*/
if (remote && pri <= PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
return (1);
return (0);
}
#define TS_RQ_PPQ (((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) + 1) / RQ_NQS)
/*
* Add a thread to the actual run-queue. Keeps transferable counts up to
* date with what is actually on the run-queue. Selects the correct
* queue position for timeshare threads.
*/
static __inline void
tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
{
struct td_sched *ts;
u_char pri;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
pri = td->td_priority;
ts = td->td_sched;
TD_SET_RUNQ(td);
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable++;
ts->ts_flags |= TSF_XFERABLE;
}
if (pri <= PRI_MAX_REALTIME) {
ts->ts_runq = &tdq->tdq_realtime;
} else if (pri <= PRI_MAX_TIMESHARE) {
ts->ts_runq = &tdq->tdq_timeshare;
KASSERT(pri <= PRI_MAX_TIMESHARE && pri >= PRI_MIN_TIMESHARE,
("Invalid priority %d on timeshare runq", pri));
/*
* This queue contains only priorities between MIN and MAX
* realtime. Use the whole queue to represent these values.
*/
if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
pri = (pri - PRI_MIN_TIMESHARE) / TS_RQ_PPQ;
pri = (pri + tdq->tdq_idx) % RQ_NQS;
/*
* This effectively shortens the queue by one so we
* can have a one slot difference between idx and
* ridx while we wait for threads to drain.
*/
if (tdq->tdq_ridx != tdq->tdq_idx &&
pri == tdq->tdq_ridx)
pri = (unsigned char)(pri - 1) % RQ_NQS;
} else
pri = tdq->tdq_ridx;
runq_add_pri(ts->ts_runq, td, pri, flags);
return;
} else
ts->ts_runq = &tdq->tdq_idle;
runq_add(ts->ts_runq, td, flags);
}
/*
* Remove a thread from a run-queue. This typically happens when a thread
* is selected to run. Running threads are not on the queue and the
* transferable count does not reflect them.
*/
static __inline void
tdq_runq_rem(struct tdq *tdq, struct thread *td)
{
struct td_sched *ts;
ts = td->td_sched;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(ts->ts_runq != NULL,
("tdq_runq_remove: thread %p null ts_runq", td));
if (ts->ts_flags & TSF_XFERABLE) {
tdq->tdq_transferable--;
ts->ts_flags &= ~TSF_XFERABLE;
}
if (ts->ts_runq == &tdq->tdq_timeshare) {
if (tdq->tdq_idx != tdq->tdq_ridx)
runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
else
runq_remove_idx(ts->ts_runq, td, NULL);
} else
runq_remove(ts->ts_runq, td);
}
/*
* Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
* for this thread to the referenced thread queue.
*/
static void
tdq_load_add(struct tdq *tdq, struct thread *td)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq->tdq_load++;
if ((td->td_proc->p_flag & P_NOLOAD) == 0)
tdq->tdq_sysload++;
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
}
/*
* Remove the load from a thread that is transitioning to a sleep state or
* exiting.
*/
static void
tdq_load_rem(struct tdq *tdq, struct thread *td)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(tdq->tdq_load != 0,
("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
tdq->tdq_load--;
if ((td->td_proc->p_flag & P_NOLOAD) == 0)
tdq->tdq_sysload--;
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
}
/*
* Set lowpri to its exact value by searching the run-queue and
* evaluating curthread. curthread may be passed as an optimization.
*/
static void
tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
if (ctd == NULL)
ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
td = tdq_choose(tdq);
if (td == NULL || td->td_priority > ctd->td_priority)
tdq->tdq_lowpri = ctd->td_priority;
else
tdq->tdq_lowpri = td->td_priority;
}
#ifdef SMP
struct cpu_search {
cpuset_t cs_mask;
u_int cs_load;
u_int cs_cpu;
int cs_limit; /* Min priority for low min load for high. */
};
#define CPU_SEARCH_LOWEST 0x1
#define CPU_SEARCH_HIGHEST 0x2
#define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
#define CPUSET_FOREACH(cpu, mask) \
for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \
if ((mask) & 1 << (cpu))
static __inline int cpu_search(struct cpu_group *cg, struct cpu_search *low,
struct cpu_search *high, const int match);
int cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low);
int cpu_search_highest(struct cpu_group *cg, struct cpu_search *high);
int cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
struct cpu_search *high);
/*
* This routine compares according to the match argument and should be
* reduced in actual instantiations via constant propagation and dead code
* elimination.
*/
static __inline int
cpu_compare(int cpu, struct cpu_search *low, struct cpu_search *high,
const int match)
{
struct tdq *tdq;
tdq = TDQ_CPU(cpu);
if (match & CPU_SEARCH_LOWEST)
if (CPU_ISSET(cpu, &low->cs_mask) &&
tdq->tdq_load < low->cs_load &&
tdq->tdq_lowpri > low->cs_limit) {
low->cs_cpu = cpu;
low->cs_load = tdq->tdq_load;
}
if (match & CPU_SEARCH_HIGHEST)
if (CPU_ISSET(cpu, &high->cs_mask) &&
tdq->tdq_load >= high->cs_limit &&
tdq->tdq_load > high->cs_load &&
tdq->tdq_transferable) {
high->cs_cpu = cpu;
high->cs_load = tdq->tdq_load;
}
return (tdq->tdq_load);
}
/*
* Search the tree of cpu_groups for the lowest or highest loaded cpu
* according to the match argument. This routine actually compares the
* load on all paths through the tree and finds the least loaded cpu on
* the least loaded path, which may differ from the least loaded cpu in
* the system. This balances work among caches and busses.
*
* This inline is instantiated in three forms below using constants for the
* match argument. It is reduced to the minimum set for each case. It is
* also recursive to the depth of the tree.
*/
static __inline int
cpu_search(struct cpu_group *cg, struct cpu_search *low,
struct cpu_search *high, const int match)
{
int total;
total = 0;
if (cg->cg_children) {
struct cpu_search lgroup;
struct cpu_search hgroup;
struct cpu_group *child;
u_int lload;
int hload;
int load;
int i;
lload = -1;
hload = -1;
for (i = 0; i < cg->cg_children; i++) {
child = &cg->cg_child[i];
if (match & CPU_SEARCH_LOWEST) {
lgroup = *low;
lgroup.cs_load = -1;
}
if (match & CPU_SEARCH_HIGHEST) {
hgroup = *high;
lgroup.cs_load = 0;
}
switch (match) {
case CPU_SEARCH_LOWEST:
load = cpu_search_lowest(child, &lgroup);
break;
case CPU_SEARCH_HIGHEST:
load = cpu_search_highest(child, &hgroup);
break;
case CPU_SEARCH_BOTH:
load = cpu_search_both(child, &lgroup, &hgroup);
break;
}
total += load;
if (match & CPU_SEARCH_LOWEST)
if (load < lload || low->cs_cpu == -1) {
*low = lgroup;
lload = load;
}
if (match & CPU_SEARCH_HIGHEST)
if (load > hload || high->cs_cpu == -1) {
hload = load;
*high = hgroup;
}
}
} else {
int cpu;
CPUSET_FOREACH(cpu, cg->cg_mask)
total += cpu_compare(cpu, low, high, match);
}
return (total);
}
/*
* cpu_search instantiations must pass constants to maintain the inline
* optimization.
*/
int
cpu_search_lowest(struct cpu_group *cg, struct cpu_search *low)
{
return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
}
int
cpu_search_highest(struct cpu_group *cg, struct cpu_search *high)
{
return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
}
int
cpu_search_both(struct cpu_group *cg, struct cpu_search *low,
struct cpu_search *high)
{
return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
}
/*
* Find the cpu with the least load via the least loaded path that has a
* lowpri greater than pri pri. A pri of -1 indicates any priority is
* acceptable.
*/
static inline int
sched_lowest(struct cpu_group *cg, cpuset_t mask, int pri)
{
struct cpu_search low;
low.cs_cpu = -1;
low.cs_load = -1;
low.cs_mask = mask;
low.cs_limit = pri;
cpu_search_lowest(cg, &low);
return low.cs_cpu;
}
/*
* Find the cpu with the highest load via the highest loaded path.
*/
static inline int
sched_highest(struct cpu_group *cg, cpuset_t mask, int minload)
{
struct cpu_search high;
high.cs_cpu = -1;
high.cs_load = 0;
high.cs_mask = mask;
high.cs_limit = minload;
cpu_search_highest(cg, &high);
return high.cs_cpu;
}
/*
* Simultaneously find the highest and lowest loaded cpu reachable via
* cg.
*/
static inline void
sched_both(struct cpu_group *cg, cpuset_t mask, int *lowcpu, int *highcpu)
{
struct cpu_search high;
struct cpu_search low;
low.cs_cpu = -1;
low.cs_limit = -1;
low.cs_load = -1;
low.cs_mask = mask;
high.cs_load = 0;
high.cs_cpu = -1;
high.cs_limit = -1;
high.cs_mask = mask;
cpu_search_both(cg, &low, &high);
*lowcpu = low.cs_cpu;
*highcpu = high.cs_cpu;
return;
}
static void
sched_balance_group(struct cpu_group *cg)
{
cpuset_t mask;
int high;
int low;
int i;
CPU_FILL(&mask);
for (;;) {
sched_both(cg, mask, &low, &high);
if (low == high || low == -1 || high == -1)
break;
if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low)))
break;
/*
* If we failed to move any threads determine which cpu
* to kick out of the set and try again.
*/
if (TDQ_CPU(high)->tdq_transferable == 0)
CPU_CLR(high, &mask);
else
CPU_CLR(low, &mask);
}
for (i = 0; i < cg->cg_children; i++)
sched_balance_group(&cg->cg_child[i]);
}
static void
sched_balance()
{
struct tdq *tdq;
/*
* Select a random time between .5 * balance_interval and
* 1.5 * balance_interval.
*/
balance_ticks = max(balance_interval / 2, 1);
balance_ticks += random() % balance_interval;
if (smp_started == 0 || rebalance == 0)
return;
tdq = TDQ_SELF();
TDQ_UNLOCK(tdq);
sched_balance_group(cpu_top);
TDQ_LOCK(tdq);
}
/*
* Lock two thread queues using their address to maintain lock order.
*/
static void
tdq_lock_pair(struct tdq *one, struct tdq *two)
{
if (one < two) {
TDQ_LOCK(one);
TDQ_LOCK_FLAGS(two, MTX_DUPOK);
} else {
TDQ_LOCK(two);
TDQ_LOCK_FLAGS(one, MTX_DUPOK);
}
}
/*
* Unlock two thread queues. Order is not important here.
*/
static void
tdq_unlock_pair(struct tdq *one, struct tdq *two)
{
TDQ_UNLOCK(one);
TDQ_UNLOCK(two);
}
/*
* Transfer load between two imbalanced thread queues.
*/
static int
sched_balance_pair(struct tdq *high, struct tdq *low)
{
int transferable;
int high_load;
int low_load;
int moved;
int move;
int diff;
int i;
tdq_lock_pair(high, low);
transferable = high->tdq_transferable;
high_load = high->tdq_load;
low_load = low->tdq_load;
moved = 0;
/*
* Determine what the imbalance is and then adjust that to how many
* threads we actually have to give up (transferable).
*/
if (transferable != 0) {
diff = high_load - low_load;
move = diff / 2;
if (diff & 0x1)
move++;
move = min(move, transferable);
for (i = 0; i < move; i++)
moved += tdq_move(high, low);
/*
* IPI the target cpu to force it to reschedule with the new
* workload.
*/
ipi_selected(1 << TDQ_ID(low), IPI_PREEMPT);
}
tdq_unlock_pair(high, low);
return (moved);
}
/*
* Move a thread from one thread queue to another.
*/
static int
tdq_move(struct tdq *from, struct tdq *to)
{
struct td_sched *ts;
struct thread *td;
struct tdq *tdq;
int cpu;
TDQ_LOCK_ASSERT(from, MA_OWNED);
TDQ_LOCK_ASSERT(to, MA_OWNED);
tdq = from;
cpu = TDQ_ID(to);
td = tdq_steal(tdq, cpu);
if (td == NULL)
return (0);
ts = td->td_sched;
/*
* Although the run queue is locked the thread may be blocked. Lock
* it to clear this and acquire the run-queue lock.
*/
thread_lock(td);
/* Drop recursive lock on from acquired via thread_lock(). */
TDQ_UNLOCK(from);
sched_rem(td);
ts->ts_cpu = cpu;
td->td_lock = TDQ_LOCKPTR(to);
tdq_add(to, td, SRQ_YIELDING);
return (1);
}
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
*/
static int
tdq_idled(struct tdq *tdq)
{
struct cpu_group *cg;
struct tdq *steal;
cpuset_t mask;
int thresh;
int cpu;
if (smp_started == 0 || steal_idle == 0)
return (1);
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
/* We don't want to be preempted while we're iterating. */
spinlock_enter();
for (cg = tdq->tdq_cg; cg != NULL; ) {
if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
thresh = steal_thresh;
else
thresh = 1;
cpu = sched_highest(cg, mask, thresh);
if (cpu == -1) {
cg = cg->cg_parent;
continue;
}
steal = TDQ_CPU(cpu);
CPU_CLR(cpu, &mask);
tdq_lock_pair(tdq, steal);
if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
tdq_unlock_pair(tdq, steal);
continue;
}
/*
* If a thread was added while interrupts were disabled don't
* steal one here. If we fail to acquire one due to affinity
* restrictions loop again with this cpu removed from the
* set.
*/
if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
tdq_unlock_pair(tdq, steal);
continue;
}
spinlock_exit();
TDQ_UNLOCK(steal);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(curthread);
return (0);
}
spinlock_exit();
return (1);
}
/*
* Notify a remote cpu of new work. Sends an IPI if criteria are met.
*/
static void
tdq_notify(struct tdq *tdq, struct thread *td)
{
struct thread *ctd;
int pri;
int cpu;
if (tdq->tdq_ipipending)
return;
cpu = td->td_sched->ts_cpu;
pri = td->td_priority;
ctd = pcpu_find(cpu)->pc_curthread;
if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
return;
if (TD_IS_IDLETHREAD(ctd)) {
/*
* If the MD code has an idle wakeup routine try that before
* falling back to IPI.
*/
if (cpu_idle_wakeup(cpu))
return;
}
tdq->tdq_ipipending = 1;
ipi_selected(1 << cpu, IPI_PREEMPT);
}
/*
* Steals load from a timeshare queue. Honors the rotating queue head
* index.
*/
static struct thread *
runq_steal_from(struct runq *rq, int cpu, u_char start)
{
struct rqbits *rqb;
struct rqhead *rqh;
struct thread *td;
int first;
int bit;
int pri;
int i;
rqb = &rq->rq_status;
bit = start & (RQB_BPW -1);
pri = 0;
first = 0;
again:
for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
if (rqb->rqb_bits[i] == 0)
continue;
if (bit != 0) {
for (pri = bit; pri < RQB_BPW; pri++)
if (rqb->rqb_bits[i] & (1ul << pri))
break;
if (pri >= RQB_BPW)
continue;
} else
pri = RQB_FFS(rqb->rqb_bits[i]);
pri += (i << RQB_L2BPW);
rqh = &rq->rq_queues[pri];
TAILQ_FOREACH(td, rqh, td_runq) {
if (first && THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
first = 1;
}
}
if (start != 0) {
start = 0;
goto again;
}
return (NULL);
}
/*
* Steals load from a standard linear queue.
*/
static struct thread *
runq_steal(struct runq *rq, int cpu)
{
struct rqhead *rqh;
struct rqbits *rqb;
struct thread *td;
int word;
int bit;
rqb = &rq->rq_status;
for (word = 0; word < RQB_LEN; word++) {
if (rqb->rqb_bits[word] == 0)
continue;
for (bit = 0; bit < RQB_BPW; bit++) {
if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
continue;
rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
TAILQ_FOREACH(td, rqh, td_runq)
if (THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
}
}
return (NULL);
}
/*
* Attempt to steal a thread in priority order from a thread queue.
*/
static struct thread *
tdq_steal(struct tdq *tdq, int cpu)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
return (td);
if ((td = runq_steal_from(&tdq->tdq_timeshare,
cpu, tdq->tdq_ridx)) != NULL)
return (td);
return (runq_steal(&tdq->tdq_idle, cpu));
}
/*
* Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
* current lock and returns with the assigned queue locked.
*/
static inline struct tdq *
sched_setcpu(struct thread *td, int cpu, int flags)
{
struct tdq *tdq;
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq = TDQ_CPU(cpu);
td->td_sched->ts_cpu = cpu;
/*
* If the lock matches just return the queue.
*/
if (td->td_lock == TDQ_LOCKPTR(tdq))
return (tdq);
#ifdef notyet
/*
* If the thread isn't running its lockptr is a
* turnstile or a sleepqueue. We can just lock_set without
* blocking.
*/
if (TD_CAN_RUN(td)) {
TDQ_LOCK(tdq);
thread_lock_set(td, TDQ_LOCKPTR(tdq));
return (tdq);
}
#endif
/*
* The hard case, migration, we need to block the thread first to
* prevent order reversals with other cpus locks.
*/
thread_lock_block(td);
TDQ_LOCK(tdq);
thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
return (tdq);
}
SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
static int
sched_pickcpu(struct thread *td, int flags)
{
struct cpu_group *cg;
struct td_sched *ts;
struct tdq *tdq;
cpuset_t mask;
int self;
int pri;
int cpu;
self = PCPU_GET(cpuid);
ts = td->td_sched;
if (smp_started == 0)
return (self);
/*
* Don't migrate a running thread from sched_switch().
*/
if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
return (ts->ts_cpu);
/*
* Prefer to run interrupt threads on the processors that generate
* the interrupt.
*/
if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
curthread->td_intr_nesting_level && ts->ts_cpu != self) {
SCHED_STAT_INC(pickcpu_intrbind);
ts->ts_cpu = self;
}
/*
* If the thread can run on the last cpu and the affinity has not
* expired or it is idle run it there.
*/
pri = td->td_priority;
tdq = TDQ_CPU(ts->ts_cpu);
if (THREAD_CAN_SCHED(td, ts->ts_cpu)) {
if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
SCHED_STAT_INC(pickcpu_idle_affinity);
return (ts->ts_cpu);
}
if (SCHED_AFFINITY(ts, CG_SHARE_L2) && tdq->tdq_lowpri > pri) {
SCHED_STAT_INC(pickcpu_affinity);
return (ts->ts_cpu);
}
}
/*
* Search for the highest level in the tree that still has affinity.
*/
cg = NULL;
for (cg = tdq->tdq_cg; cg != NULL; cg = cg->cg_parent)
if (SCHED_AFFINITY(ts, cg->cg_level))
break;
cpu = -1;
mask = td->td_cpuset->cs_mask;
if (cg)
cpu = sched_lowest(cg, mask, pri);
if (cpu == -1)
cpu = sched_lowest(cpu_top, mask, -1);
/*
* Compare the lowest loaded cpu to current cpu.
*/
if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) {
SCHED_STAT_INC(pickcpu_local);
cpu = self;
} else
SCHED_STAT_INC(pickcpu_lowest);
if (cpu != ts->ts_cpu)
SCHED_STAT_INC(pickcpu_migration);
KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
return (cpu);
}
#endif
/*
* Pick the highest priority task we have and return it.
*/
static struct thread *
tdq_choose(struct tdq *tdq)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
td = runq_choose(&tdq->tdq_realtime);
if (td != NULL)
return (td);
td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
if (td != NULL) {
KASSERT(td->td_priority >= PRI_MIN_TIMESHARE,
("tdq_choose: Invalid priority on timeshare queue %d",
td->td_priority));
return (td);
}
td = runq_choose(&tdq->tdq_idle);
if (td != NULL) {
KASSERT(td->td_priority >= PRI_MIN_IDLE,
("tdq_choose: Invalid priority on idle queue %d",
td->td_priority));
return (td);
}
return (NULL);
}
/*
* Initialize a thread queue.
*/
static void
tdq_setup(struct tdq *tdq)
{
if (bootverbose)
printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
runq_init(&tdq->tdq_realtime);
runq_init(&tdq->tdq_timeshare);
runq_init(&tdq->tdq_idle);
snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
"sched lock %d", (int)TDQ_ID(tdq));
mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
MTX_SPIN | MTX_RECURSE);
#ifdef KTR
snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
"CPU %d load", (int)TDQ_ID(tdq));
#endif
}
#ifdef SMP
static void
sched_setup_smp(void)
{
struct tdq *tdq;
int i;
cpu_top = smp_topo();
for (i = 0; i < MAXCPU; i++) {
if (CPU_ABSENT(i))
continue;
tdq = TDQ_CPU(i);
tdq_setup(tdq);
tdq->tdq_cg = smp_topo_find(cpu_top, i);
if (tdq->tdq_cg == NULL)
panic("Can't find cpu group for %d\n", i);
}
balance_tdq = TDQ_SELF();
sched_balance();
}
#endif
/*
* Setup the thread queues and initialize the topology based on MD
* information.
*/
static void
sched_setup(void *dummy)
{
struct tdq *tdq;
tdq = TDQ_SELF();
#ifdef SMP
sched_setup_smp();
#else
tdq_setup(tdq);
#endif
/*
* To avoid divide-by-zero, we set realstathz a dummy value
* in case which sched_clock() called before sched_initticks().
*/
realstathz = hz;
sched_slice = (realstathz/10); /* ~100ms */
tickincr = 1 << SCHED_TICK_SHIFT;
/* Add thread0's load since it's running. */
TDQ_LOCK(tdq);
thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
tdq_load_add(tdq, &thread0);
tdq->tdq_lowpri = thread0.td_priority;
TDQ_UNLOCK(tdq);
}
/*
* This routine determines the tickincr after stathz and hz are setup.
*/
/* ARGSUSED */
static void
sched_initticks(void *dummy)
{
int incr;
realstathz = stathz ? stathz : hz;
sched_slice = (realstathz/10); /* ~100ms */
/*
* tickincr is shifted out by 10 to avoid rounding errors due to
* hz not being evenly divisible by stathz on all platforms.
*/
incr = (hz << SCHED_TICK_SHIFT) / realstathz;
/*
* This does not work for values of stathz that are more than
* 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
*/
if (incr == 0)
incr = 1;
tickincr = incr;
#ifdef SMP
/*
* Set the default balance interval now that we know
* what realstathz is.
*/
balance_interval = realstathz;
/*
* Set steal thresh to roughly log2(mp_ncpu) but no greater than 4.
* This prevents excess thrashing on large machines and excess idle
* on smaller machines.
*/
steal_thresh = min(fls(mp_ncpus) - 1, 3);
affinity = SCHED_AFFINITY_DEFAULT;
#endif
}
/*
* This is the core of the interactivity algorithm. Determines a score based
* on past behavior. It is the ratio of sleep time to run time scaled to
* a [0, 100] integer. This is the voluntary sleep time of a process, which
* differs from the cpu usage because it does not account for time spent
* waiting on a run-queue. Would be prettier if we had floating point.
*/
static int
sched_interact_score(struct thread *td)
{
struct td_sched *ts;
int div;
ts = td->td_sched;
/*
* The score is only needed if this is likely to be an interactive
* task. Don't go through the expense of computing it if there's
* no chance.
*/
if (sched_interact <= SCHED_INTERACT_HALF &&
ts->ts_runtime >= ts->ts_slptime)
return (SCHED_INTERACT_HALF);
if (ts->ts_runtime > ts->ts_slptime) {
div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
return (SCHED_INTERACT_HALF +
(SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
}
if (ts->ts_slptime > ts->ts_runtime) {
div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
return (ts->ts_runtime / div);
}
/* runtime == slptime */
if (ts->ts_runtime)
return (SCHED_INTERACT_HALF);
/*
* This can happen if slptime and runtime are 0.
*/
return (0);
}
/*
* Scale the scheduling priority according to the "interactivity" of this
* process.
*/
static void
sched_priority(struct thread *td)
{
int score;
int pri;
if (td->td_pri_class != PRI_TIMESHARE)
return;
/*
* If the score is interactive we place the thread in the realtime
* queue with a priority that is less than kernel and interrupt
* priorities. These threads are not subject to nice restrictions.
*
* Scores greater than this are placed on the normal timeshare queue
* where the priority is partially decided by the most recent cpu
* utilization and the rest is decided by nice value.
*
* The nice value of the process has a linear effect on the calculated
* score. Negative nice values make it easier for a thread to be
* considered interactive.
*/
score = imax(0, sched_interact_score(td) - td->td_proc->p_nice);
if (score < sched_interact) {
pri = PRI_MIN_REALTIME;
pri += ((PRI_MAX_REALTIME - PRI_MIN_REALTIME) / sched_interact)
* score;
KASSERT(pri >= PRI_MIN_REALTIME && pri <= PRI_MAX_REALTIME,
("sched_priority: invalid interactive priority %d score %d",
pri, score));
} else {
pri = SCHED_PRI_MIN;
if (td->td_sched->ts_ticks)
pri += SCHED_PRI_TICKS(td->td_sched);
pri += SCHED_PRI_NICE(td->td_proc->p_nice);
KASSERT(pri >= PRI_MIN_TIMESHARE && pri <= PRI_MAX_TIMESHARE,
("sched_priority: invalid priority %d: nice %d, "
"ticks %d ftick %d ltick %d tick pri %d",
pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
td->td_sched->ts_ftick, td->td_sched->ts_ltick,
SCHED_PRI_TICKS(td->td_sched)));
}
sched_user_prio(td, pri);
return;
}
/*
* This routine enforces a maximum limit on the amount of scheduling history
* kept. It is called after either the slptime or runtime is adjusted. This
* function is ugly due to integer math.
*/
static void
sched_interact_update(struct thread *td)
{
struct td_sched *ts;
u_int sum;
ts = td->td_sched;
sum = ts->ts_runtime + ts->ts_slptime;
if (sum < SCHED_SLP_RUN_MAX)
return;
/*
* This only happens from two places:
* 1) We have added an unusual amount of run time from fork_exit.
* 2) We have added an unusual amount of sleep time from sched_sleep().
*/
if (sum > SCHED_SLP_RUN_MAX * 2) {
if (ts->ts_runtime > ts->ts_slptime) {
ts->ts_runtime = SCHED_SLP_RUN_MAX;
ts->ts_slptime = 1;
} else {
ts->ts_slptime = SCHED_SLP_RUN_MAX;
ts->ts_runtime = 1;
}
return;
}
/*
* If we have exceeded by more than 1/5th then the algorithm below
* will not bring us back into range. Dividing by two here forces
* us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
*/
if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
ts->ts_runtime /= 2;
ts->ts_slptime /= 2;
return;
}
ts->ts_runtime = (ts->ts_runtime / 5) * 4;
ts->ts_slptime = (ts->ts_slptime / 5) * 4;
}
/*
* Scale back the interactivity history when a child thread is created. The
* history is inherited from the parent but the thread may behave totally
* differently. For example, a shell spawning a compiler process. We want
* to learn that the compiler is behaving badly very quickly.
*/
static void
sched_interact_fork(struct thread *td)
{
int ratio;
int sum;
sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
if (sum > SCHED_SLP_RUN_FORK) {
ratio = sum / SCHED_SLP_RUN_FORK;
td->td_sched->ts_runtime /= ratio;
td->td_sched->ts_slptime /= ratio;
}
}
/*
* Called from proc0_init() to setup the scheduler fields.
*/
void
schedinit(void)
{
/*
* Set up the scheduler specific parts of proc0.
*/
proc0.p_sched = NULL; /* XXX */
thread0.td_sched = &td_sched0;
td_sched0.ts_ltick = ticks;
td_sched0.ts_ftick = ticks;
td_sched0.ts_slice = sched_slice;
}
/*
* This is only somewhat accurate since given many processes of the same
* priority they will switch when their slices run out, which will be
* at most sched_slice stathz ticks.
*/
int
sched_rr_interval(void)
{
/* Convert sched_slice to hz */
return (hz/(realstathz/sched_slice));
}
/*
* Update the percent cpu tracking information when it is requested or
* the total history exceeds the maximum. We keep a sliding history of
* tick counts that slowly decays. This is less precise than the 4BSD
* mechanism since it happens with less regular and frequent events.
*/
static void
sched_pctcpu_update(struct td_sched *ts)
{
if (ts->ts_ticks == 0)
return;
if (ticks - (hz / 10) < ts->ts_ltick &&
SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
return;
/*
* Adjust counters and watermark for pctcpu calc.
*/
if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
SCHED_TICK_TARG;
else
ts->ts_ticks = 0;
ts->ts_ltick = ticks;
ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
}
/*
* Adjust the priority of a thread. Move it to the appropriate run-queue
* if necessary. This is the back-end for several priority related
* functions.
*/
static void
sched_thread_priority(struct thread *td, u_char prio)
{
struct td_sched *ts;
struct tdq *tdq;
int oldpri;
KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
"prio:%d", td->td_priority, "new prio:%d", prio,
KTR_ATTR_LINKED, sched_tdname(curthread));
if (td != curthread && prio > td->td_priority) {
KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
"lend prio", "prio:%d", td->td_priority, "new prio:%d",
prio, KTR_ATTR_LINKED, sched_tdname(td));
}
ts = td->td_sched;
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_priority == prio)
return;
/*
* If the priority has been elevated due to priority
* propagation, we may have to move ourselves to a new
* queue. This could be optimized to not re-add in some
* cases.
*/
if (TD_ON_RUNQ(td) && prio < td->td_priority) {
sched_rem(td);
td->td_priority = prio;
sched_add(td, SRQ_BORROWING);
return;
}
/*
* If the thread is currently running we may have to adjust the lowpri
* information so other cpus are aware of our current priority.
*/
if (TD_IS_RUNNING(td)) {
tdq = TDQ_CPU(ts->ts_cpu);
oldpri = td->td_priority;
td->td_priority = prio;
if (prio < tdq->tdq_lowpri)
tdq->tdq_lowpri = prio;
else if (tdq->tdq_lowpri == oldpri)
tdq_setlowpri(tdq, td);
return;
}
td->td_priority = prio;
}
/*
* Update a thread's priority when it is lent another thread's
* priority.
*/
void
sched_lend_prio(struct thread *td, u_char prio)
{
td->td_flags |= TDF_BORROWING;
sched_thread_priority(td, prio);
}
/*
* Restore a thread's priority when priority propagation is
* over. The prio argument is the minimum priority the thread
* needs to have to satisfy other possible priority lending
* requests. If the thread's regular priority is less
* important than prio, the thread will keep a priority boost
* of prio.
*/
void
sched_unlend_prio(struct thread *td, u_char prio)
{
u_char base_pri;
if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
td->td_base_pri <= PRI_MAX_TIMESHARE)
base_pri = td->td_user_pri;
else
base_pri = td->td_base_pri;
if (prio >= base_pri) {
td->td_flags &= ~TDF_BORROWING;
sched_thread_priority(td, base_pri);
} else
sched_lend_prio(td, prio);
}
/*
* Standard entry for setting the priority to an absolute value.
*/
void
sched_prio(struct thread *td, u_char prio)
{
u_char oldprio;
/* First, update the base priority. */
td->td_base_pri = prio;
/*
* If the thread is borrowing another thread's priority, don't
* ever lower the priority.
*/
if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
return;
/* Change the real priority. */
oldprio = td->td_priority;
sched_thread_priority(td, prio);
/*
* If the thread is on a turnstile, then let the turnstile update
* its state.
*/
if (TD_ON_LOCK(td) && oldprio != prio)
turnstile_adjust(td, oldprio);
}
/*
* Set the base user priority, does not effect current running priority.
*/
void
sched_user_prio(struct thread *td, u_char prio)
{
u_char oldprio;
td->td_base_user_pri = prio;
if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
return;
oldprio = td->td_user_pri;
td->td_user_pri = prio;
}
void
sched_lend_user_prio(struct thread *td, u_char prio)
{
u_char oldprio;
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_flags |= TDF_UBORROWING;
oldprio = td->td_user_pri;
td->td_user_pri = prio;
}
void
sched_unlend_user_prio(struct thread *td, u_char prio)
{
u_char base_pri;
THREAD_LOCK_ASSERT(td, MA_OWNED);
base_pri = td->td_base_user_pri;
if (prio >= base_pri) {
td->td_flags &= ~TDF_UBORROWING;
sched_user_prio(td, base_pri);
} else {
sched_lend_user_prio(td, prio);
}
}
/*
* Block a thread for switching. Similar to thread_block() but does not
* bump the spin count.
*/
static inline struct mtx *
thread_block_switch(struct thread *td)
{
struct mtx *lock;
THREAD_LOCK_ASSERT(td, MA_OWNED);
lock = td->td_lock;
td->td_lock = &blocked_lock;
mtx_unlock_spin(lock);
return (lock);
}
/*
* Handle migration from sched_switch(). This happens only for
* cpu binding.
*/
static struct mtx *
sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
{
struct tdq *tdn;
tdn = TDQ_CPU(td->td_sched->ts_cpu);
#ifdef SMP
tdq_load_rem(tdq, td);
/*
* Do the lock dance required to avoid LOR. We grab an extra
* spinlock nesting to prevent preemption while we're
* not holding either run-queue lock.
*/
spinlock_enter();
thread_block_switch(td); /* This releases the lock on tdq. */
/*
* Acquire both run-queue locks before placing the thread on the new
* run-queue to avoid deadlocks created by placing a thread with a
* blocked lock on the run-queue of a remote processor. The deadlock
* occurs when a third processor attempts to lock the two queues in
* question while the target processor is spinning with its own
* run-queue lock held while waiting for the blocked lock to clear.
*/
tdq_lock_pair(tdn, tdq);
tdq_add(tdn, td, flags);
tdq_notify(tdn, td);
TDQ_UNLOCK(tdn);
spinlock_exit();
#endif
return (TDQ_LOCKPTR(tdn));
}
/*
* Release a thread that was blocked with thread_block_switch().
*/
static inline void
thread_unblock_switch(struct thread *td, struct mtx *mtx)
{
atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
(uintptr_t)mtx);
}
/*
* Switch threads. This function has to handle threads coming in while
* blocked for some reason, running, or idle. It also must deal with
* migrating a thread from one queue to another as running threads may
* be assigned elsewhere via binding.
*/
void
sched_switch(struct thread *td, struct thread *newtd, int flags)
{
struct tdq *tdq;
struct td_sched *ts;
struct mtx *mtx;
int srqflag;
int cpuid;
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
ts = td->td_sched;
mtx = td->td_lock;
ts->ts_rltick = ticks;
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
td->td_flags &= ~TDF_NEEDRESCHED;
td->td_owepreempt = 0;
tdq->tdq_switchcnt++;
/*
* The lock pointer in an idle thread should never change. Reset it
* to CAN_RUN as well.
*/
if (TD_IS_IDLETHREAD(td)) {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
TD_SET_CAN_RUN(td);
} else if (TD_IS_RUNNING(td)) {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
srqflag = (flags & SW_PREEMPT) ?
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
SRQ_OURSELF|SRQ_YIELDING;
if (ts->ts_cpu == cpuid)
tdq_runq_add(tdq, td, srqflag);
else
mtx = sched_switch_migrate(tdq, td, srqflag);
} else {
/* This thread must be going to sleep. */
TDQ_LOCK(tdq);
mtx = thread_block_switch(td);
tdq_load_rem(tdq, td);
}
/*
* We enter here with the thread blocked and assigned to the
* appropriate cpu run-queue or sleep-queue and with the current
* thread-queue locked.
*/
TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
newtd = choosethread();
/*
* Call the MD code to switch contexts if necessary.
*/
if (td != newtd) {
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
#endif
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
#ifdef KDTRACE_HOOKS
/*
* If DTrace has set the active vtime enum to anything
* other than INACTIVE (0), then it should have set the
* function to call.
*/
if (dtrace_vtime_active)
(*dtrace_vtime_switch_func)(newtd);
#endif
cpu_switch(td, newtd, mtx);
/*
* We may return from cpu_switch on a different cpu. However,
* we always return with td_lock pointing to the current cpu's
* run queue lock.
*/
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
#endif
} else
thread_unblock_switch(td, mtx);
/*
* Assert that all went well and return.
*/
TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
td->td_oncpu = cpuid;
}
/*
* Adjust thread priorities as a result of a nice request.
*/
void
sched_nice(struct proc *p, int nice)
{
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_nice = nice;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
sched_priority(td);
sched_prio(td, td->td_base_user_pri);
thread_unlock(td);
}
}
/*
* Record the sleep time for the interactivity scorer.
*/
void
sched_sleep(struct thread *td, int prio)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_slptick = ticks;
if (TD_IS_SUSPENDED(td) || prio <= PSOCK)
td->td_flags |= TDF_CANSWAP;
if (static_boost == 1 && prio)
sched_prio(td, prio);
else if (static_boost && td->td_priority > static_boost)
sched_prio(td, static_boost);
}
/*
* Schedule a thread to resume execution and record how long it voluntarily
* slept. We also update the pctcpu, interactivity, and priority.
*/
void
sched_wakeup(struct thread *td)
{
struct td_sched *ts;
int slptick;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
td->td_flags &= ~TDF_CANSWAP;
/*
* If we slept for more than a tick update our interactivity and
* priority.
*/
slptick = td->td_slptick;
td->td_slptick = 0;
if (slptick && slptick != ticks) {
u_int hzticks;
hzticks = (ticks - slptick) << SCHED_TICK_SHIFT;
ts->ts_slptime += hzticks;
sched_interact_update(td);
sched_pctcpu_update(ts);
}
/* Reset the slice value after we sleep. */
ts->ts_slice = sched_slice;
sched_add(td, SRQ_BORING);
}
/*
* Penalize the parent for creating a new child and initialize the child's
* priority.
*/
void
sched_fork(struct thread *td, struct thread *child)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
sched_fork_thread(td, child);
/*
* Penalize the parent and child for forking.
*/
sched_interact_fork(child);
sched_priority(child);
td->td_sched->ts_runtime += tickincr;
sched_interact_update(td);
sched_priority(td);
}
/*
* Fork a new thread, may be within the same process.
*/
void
sched_fork_thread(struct thread *td, struct thread *child)
{
struct td_sched *ts;
struct td_sched *ts2;
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* Initialize child.
*/
ts = td->td_sched;
ts2 = child->td_sched;
child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
child->td_cpuset = cpuset_ref(td->td_cpuset);
ts2->ts_cpu = ts->ts_cpu;
ts2->ts_flags = 0;
/*
* Grab our parents cpu estimation information and priority.
*/
ts2->ts_ticks = ts->ts_ticks;
ts2->ts_ltick = ts->ts_ltick;
ts2->ts_ftick = ts->ts_ftick;
child->td_user_pri = td->td_user_pri;
child->td_base_user_pri = td->td_base_user_pri;
/*
* And update interactivity score.
*/
ts2->ts_slptime = ts->ts_slptime;
ts2->ts_runtime = ts->ts_runtime;
ts2->ts_slice = 1; /* Attempt to quickly learn interactivity. */
#ifdef KTR
bzero(ts2->ts_name, sizeof(ts2->ts_name));
#endif
}
/*
* Adjust the priority class of a thread.
*/
void
sched_class(struct thread *td, int class)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_pri_class == class)
return;
td->td_pri_class = class;
}
/*
* Return some of the child's priority and interactivity to the parent.
*/
void
sched_exit(struct proc *p, struct thread *child)
{
struct thread *td;
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
"prio:td", child->td_priority);
PROC_LOCK_ASSERT(p, MA_OWNED);
td = FIRST_THREAD_IN_PROC(p);
sched_exit_thread(td, child);
}
/*
* Penalize another thread for the time spent on this one. This helps to
* worsen the priority and interactivity of processes which schedule batch
* jobs such as make. This has little effect on the make process itself but
* causes new processes spawned by it to receive worse scores immediately.
*/
void
sched_exit_thread(struct thread *td, struct thread *child)
{
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
"prio:td", child->td_priority);
/*
* Give the child's runtime to the parent without returning the
* sleep time as a penalty to the parent. This causes shells that
* launch expensive things to mark their children as expensive.
*/
thread_lock(td);
td->td_sched->ts_runtime += child->td_sched->ts_runtime;
sched_interact_update(td);
sched_priority(td);
thread_unlock(td);
}
void
sched_preempt(struct thread *td)
{
struct tdq *tdq;
thread_lock(td);
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
tdq->tdq_ipipending = 0;
if (td->td_priority > tdq->tdq_lowpri) {
int flags;
flags = SW_INVOL | SW_PREEMPT;
if (td->td_critnest > 1)
td->td_owepreempt = 1;
else if (TD_IS_IDLETHREAD(td))
mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
else
mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
}
thread_unlock(td);
}
/*
* Fix priorities on return to user-space. Priorities may be elevated due
* to static priorities in msleep() or similar.
*/
void
sched_userret(struct thread *td)
{
/*
* XXX we cheat slightly on the locking here to avoid locking in
* the usual case. Setting td_priority here is essentially an
* incomplete workaround for not setting it properly elsewhere.
* Now that some interrupt handlers are threads, not setting it
* properly elsewhere can clobber it in the window between setting
* it here and returning to user mode, so don't waste time setting
* it perfectly here.
*/
KASSERT((td->td_flags & TDF_BORROWING) == 0,
("thread with borrowed priority returning to userland"));
if (td->td_priority != td->td_user_pri) {
thread_lock(td);
td->td_priority = td->td_user_pri;
td->td_base_pri = td->td_user_pri;
tdq_setlowpri(TDQ_SELF(), td);
thread_unlock(td);
}
}
/*
* Handle a stathz tick. This is really only relevant for timeshare
* threads.
*/
void
sched_clock(struct thread *td)
{
struct tdq *tdq;
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq = TDQ_SELF();
#ifdef SMP
/*
* We run the long term load balancer infrequently on the first cpu.
*/
if (balance_tdq == tdq) {
if (balance_ticks && --balance_ticks == 0)
sched_balance();
}
#endif
/*
* Save the old switch count so we have a record of the last ticks
* activity. Initialize the new switch count based on our load.
* If there is some activity seed it to reflect that.
*/
tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
tdq->tdq_switchcnt = tdq->tdq_load;
/*
* Advance the insert index once for each tick to ensure that all
* threads get a chance to run.
*/
if (tdq->tdq_idx == tdq->tdq_ridx) {
tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
tdq->tdq_ridx = tdq->tdq_idx;
}
ts = td->td_sched;
if (td->td_pri_class & PRI_FIFO_BIT)
return;
if (td->td_pri_class == PRI_TIMESHARE) {
/*
* We used a tick; charge it to the thread so
* that we can compute our interactivity.
*/
td->td_sched->ts_runtime += tickincr;
sched_interact_update(td);
sched_priority(td);
}
/*
* We used up one time slice.
*/
if (--ts->ts_slice > 0)
return;
/*
* We're out of time, force a requeue at userret().
*/
ts->ts_slice = sched_slice;
td->td_flags |= TDF_NEEDRESCHED;
}
/*
* Called once per hz tick. Used for cpu utilization information. This
* is easier than trying to scale based on stathz.
*/
void
sched_tick(void)
{
struct td_sched *ts;
ts = curthread->td_sched;
/*
* Ticks is updated asynchronously on a single cpu. Check here to
* avoid incrementing ts_ticks multiple times in a single tick.
*/
if (ts->ts_ltick == ticks)
return;
/* Adjust ticks for pctcpu */
ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
ts->ts_ltick = ticks;
/*
* Update if we've exceeded our desired tick threshhold by over one
* second.
*/
if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
sched_pctcpu_update(ts);
}
/*
* Return whether the current CPU has runnable tasks. Used for in-kernel
* cooperative idle threads.
*/
int
sched_runnable(void)
{
struct tdq *tdq;
int load;
load = 1;
tdq = TDQ_SELF();
if ((curthread->td_flags & TDF_IDLETD) != 0) {
if (tdq->tdq_load > 0)
goto out;
} else
if (tdq->tdq_load - 1 > 0)
goto out;
load = 0;
out:
return (load);
}
/*
* Choose the highest priority thread to run. The thread is removed from
* the run-queue while running however the load remains. For SMP we set
* the tdq in the global idle bitmask if it idles here.
*/
struct thread *
sched_choose(void)
{
struct thread *td;
struct tdq *tdq;
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
td = tdq_choose(tdq);
if (td) {
td->td_sched->ts_ltick = ticks;
tdq_runq_rem(tdq, td);
tdq->tdq_lowpri = td->td_priority;
return (td);
}
tdq->tdq_lowpri = PRI_MAX_IDLE;
return (PCPU_GET(idlethread));
}
/*
* Set owepreempt if necessary. Preemption never happens directly in ULE,
* we always request it once we exit a critical section.
*/
static inline void
sched_setpreempt(struct thread *td)
{
struct thread *ctd;
int cpri;
int pri;
THREAD_LOCK_ASSERT(curthread, MA_OWNED);
ctd = curthread;
pri = td->td_priority;
cpri = ctd->td_priority;
if (pri < cpri)
ctd->td_flags |= TDF_NEEDRESCHED;
if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
return;
if (!sched_shouldpreempt(pri, cpri, 0))
return;
ctd->td_owepreempt = 1;
}
/*
* Add a thread to a thread queue. Select the appropriate runq and add the
* thread to it. This is the internal function called when the tdq is
* predetermined.
*/
void
tdq_add(struct tdq *tdq, struct thread *td, int flags)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT((td->td_inhibitors == 0),
("sched_add: trying to run inhibited thread"));
KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
("sched_add: bad thread state"));
KASSERT(td->td_flags & TDF_INMEM,
("sched_add: thread swapped out"));
if (td->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = td->td_priority;
tdq_runq_add(tdq, td, flags);
tdq_load_add(tdq, td);
}
/*
* Select the target thread queue and add a thread to it. Request
* preemption or IPI a remote processor if required.
*/
void
sched_add(struct thread *td, int flags)
{
struct tdq *tdq;
#ifdef SMP
int cpu;
#endif
KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
"prio:%d", td->td_priority, KTR_ATTR_LINKED,
sched_tdname(curthread));
KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
KTR_ATTR_LINKED, sched_tdname(td));
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* Recalculate the priority before we select the target cpu or
* run-queue.
*/
if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
sched_priority(td);
#ifdef SMP
/*
* Pick the destination cpu and if it isn't ours transfer to the
* target cpu.
*/
cpu = sched_pickcpu(td, flags);
tdq = sched_setcpu(td, cpu, flags);
tdq_add(tdq, td, flags);
if (cpu != PCPU_GET(cpuid)) {
tdq_notify(tdq, td);
return;
}
#else
tdq = TDQ_SELF();
TDQ_LOCK(tdq);
/*
* Now that the thread is moving to the run-queue, set the lock
* to the scheduler's lock.
*/
thread_lock_set(td, TDQ_LOCKPTR(tdq));
tdq_add(tdq, td, flags);
#endif
if (!(flags & SRQ_YIELDING))
sched_setpreempt(td);
}
/*
* Remove a thread from a run-queue without running it. This is used
* when we're stealing a thread from a remote queue. Otherwise all threads
* exit by calling sched_exit_thread() and sched_throw() themselves.
*/
void
sched_rem(struct thread *td)
{
struct tdq *tdq;
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
"prio:%d", td->td_priority);
tdq = TDQ_CPU(td->td_sched->ts_cpu);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
KASSERT(TD_ON_RUNQ(td),
("sched_rem: thread not on run queue"));
tdq_runq_rem(tdq, td);
tdq_load_rem(tdq, td);
TD_SET_CAN_RUN(td);
if (td->td_priority == tdq->tdq_lowpri)
tdq_setlowpri(tdq, NULL);
}
/*
* Fetch cpu utilization information. Updates on demand.
*/
fixpt_t
sched_pctcpu(struct thread *td)
{
fixpt_t pctcpu;
struct td_sched *ts;
pctcpu = 0;
ts = td->td_sched;
if (ts == NULL)
return (0);
thread_lock(td);
if (ts->ts_ticks) {
int rtick;
sched_pctcpu_update(ts);
/* How many rtick per second ? */
rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
}
thread_unlock(td);
return (pctcpu);
}
/*
* Enforce affinity settings for a thread. Called after adjustments to
* cpumask.
*/
void
sched_affinity(struct thread *td)
{
#ifdef SMP
struct td_sched *ts;
int cpu;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
if (THREAD_CAN_SCHED(td, ts->ts_cpu))
return;
if (TD_ON_RUNQ(td)) {
sched_rem(td);
sched_add(td, SRQ_BORING);
return;
}
if (!TD_IS_RUNNING(td))
return;
td->td_flags |= TDF_NEEDRESCHED;
if (!THREAD_CAN_MIGRATE(td))
return;
/*
* Assign the new cpu and force a switch before returning to
* userspace. If the target thread is not running locally send
* an ipi to force the issue.
*/
cpu = ts->ts_cpu;
ts->ts_cpu = sched_pickcpu(td, 0);
if (cpu != PCPU_GET(cpuid))
ipi_selected(1 << cpu, IPI_PREEMPT);
#endif
}
/*
* Bind a thread to a target cpu.
*/
void
sched_bind(struct thread *td, int cpu)
{
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
ts = td->td_sched;
if (ts->ts_flags & TSF_BOUND)
sched_unbind(td);
ts->ts_flags |= TSF_BOUND;
sched_pin();
if (PCPU_GET(cpuid) == cpu)
return;
ts->ts_cpu = cpu;
/* When we return from mi_switch we'll be on the correct cpu. */
mi_switch(SW_VOL, NULL);
}
/*
* Release a bound thread.
*/
void
sched_unbind(struct thread *td)
{
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
if ((ts->ts_flags & TSF_BOUND) == 0)
return;
ts->ts_flags &= ~TSF_BOUND;
sched_unpin();
}
int
sched_is_bound(struct thread *td)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
return (td->td_sched->ts_flags & TSF_BOUND);
}
/*
* Basic yield call.
*/
void
sched_relinquish(struct thread *td)
{
thread_lock(td);
mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
thread_unlock(td);
}
/*
* Return the total system load.
*/
int
sched_load(void)
{
#ifdef SMP
int total;
int i;
total = 0;
for (i = 0; i <= mp_maxid; i++)
total += TDQ_CPU(i)->tdq_sysload;
return (total);
#else
return (TDQ_SELF()->tdq_sysload);
#endif
}
int
sched_sizeof_proc(void)
{
return (sizeof(struct proc));
}
int
sched_sizeof_thread(void)
{
return (sizeof(struct thread) + sizeof(struct td_sched));
}
#ifdef SMP
#define TDQ_IDLESPIN(tdq) \
((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
#else
#define TDQ_IDLESPIN(tdq) 1
#endif
/*
* The actual idle process.
*/
void
sched_idletd(void *dummy)
{
struct thread *td;
struct tdq *tdq;
int switchcnt;
int i;
mtx_assert(&Giant, MA_NOTOWNED);
td = curthread;
tdq = TDQ_SELF();
for (;;) {
#ifdef SMP
if (tdq_idled(tdq) == 0)
continue;
#endif
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
/*
* If we're switching very frequently, spin while checking
* for load rather than entering a low power state that
* may require an IPI. However, don't do any busy
* loops while on SMT machines as this simply steals
* cycles from cores doing useful work.
*/
if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
for (i = 0; i < sched_idlespins; i++) {
if (tdq->tdq_load)
break;
cpu_spinwait();
}
}
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
if (tdq->tdq_load == 0)
cpu_idle(switchcnt > 1);
if (tdq->tdq_load) {
thread_lock(td);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(td);
}
}
}
/*
* A CPU is entering for the first time or a thread is exiting.
*/
void
sched_throw(struct thread *td)
{
struct thread *newtd;
struct tdq *tdq;
tdq = TDQ_SELF();
if (td == NULL) {
/* Correct spinlock nesting and acquire the correct lock. */
TDQ_LOCK(tdq);
spinlock_exit();
} else {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
tdq_load_rem(tdq, td);
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
}
KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
newtd = choosethread();
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
PCPU_SET(switchtime, cpu_ticks());
PCPU_SET(switchticks, ticks);
cpu_throw(td, newtd); /* doesn't return */
}
/*
* This is called from fork_exit(). Just acquire the correct locks and
* let fork do the rest of the work.
*/
void
sched_fork_exit(struct thread *td)
{
struct td_sched *ts;
struct tdq *tdq;
int cpuid;
/*
* Finish setting up thread glue so that it begins execution in a
* non-nested critical section with the scheduler lock held.
*/
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
ts = td->td_sched;
if (TD_IS_IDLETHREAD(td))
td->td_lock = TDQ_LOCKPTR(tdq);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
td->td_oncpu = cpuid;
TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
}
/*
* Create on first use to catch odd startup conditons.
*/
char *
sched_tdname(struct thread *td)
{
#ifdef KTR
struct td_sched *ts;
ts = td->td_sched;
if (ts->ts_name[0] == '\0')
snprintf(ts->ts_name, sizeof(ts->ts_name),
"%s tid %d", td->td_name, td->td_tid);
return (ts->ts_name);
#else
return (td->td_name);
#endif
}
#ifdef SMP
/*
* Build the CPU topology dump string. Is recursively called to collect
* the topology tree.
*/
static int
sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
int indent)
{
int i, first;
sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
"", indent, cg->cg_level);
sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"0x%x\">", indent, "",
cg->cg_count, cg->cg_mask);
first = TRUE;
for (i = 0; i < MAXCPU; i++) {
if ((cg->cg_mask & (1 << i)) != 0) {
if (!first)
sbuf_printf(sb, ", ");
else
first = FALSE;
sbuf_printf(sb, "%d", i);
}
}
sbuf_printf(sb, "</cpu>\n");
sbuf_printf(sb, "%*s <flags>", indent, "");
if (cg->cg_flags != 0) {
if ((cg->cg_flags & CG_FLAG_HTT) != 0)
sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>\n");
if ((cg->cg_flags & CG_FLAG_SMT) != 0)
sbuf_printf(sb, "<flag name=\"THREAD\">SMT group</flag>\n");
}
sbuf_printf(sb, "</flags>\n");
if (cg->cg_children > 0) {
sbuf_printf(sb, "%*s <children>\n", indent, "");
for (i = 0; i < cg->cg_children; i++)
sysctl_kern_sched_topology_spec_internal(sb,
&cg->cg_child[i], indent+2);
sbuf_printf(sb, "%*s </children>\n", indent, "");
}
sbuf_printf(sb, "%*s</group>\n", indent, "");
return (0);
}
/*
* Sysctl handler for retrieving topology dump. It's a wrapper for
* the recursive sysctl_kern_smp_topology_spec_internal().
*/
static int
sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
{
struct sbuf *topo;
int err;
KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
if (topo == NULL)
return (ENOMEM);
sbuf_printf(topo, "<groups>\n");
err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
sbuf_printf(topo, "</groups>\n");
if (err == 0) {
sbuf_finish(topo);
err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
}
sbuf_delete(topo);
return (err);
}
#endif
SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
"Scheduler name");
SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
"Slice size for timeshare threads");
SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
"Interactivity score threshold");
SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, &preempt_thresh,
0,"Min priority for preemption, lower priorities have greater precedence");
SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost,
0,"Controls whether static kernel priorities are assigned to sleeping threads.");
SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins,
0,"Number of times idle will spin waiting for new work.");
SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, &sched_idlespinthresh,
0,"Threshold before we will permit idle spinning.");
#ifdef SMP
SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
"Number of hz ticks to keep thread affinity for");
SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
"Enables the long-term load balancer");
SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
&balance_interval, 0,
"Average frequency in stathz ticks to run the long-term balancer");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0,
"Steals work from another hyper-threaded core on idle");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
"Attempts to steal work from other cores before idling");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
"Minimum load on remote cpu before we'll steal");
/* Retrieve SMP topology */
SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
"XML dump of detected CPU topology");
#endif
/* ps compat. All cpu percentages from ULE are weighted. */
static int ccpu = 0;
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
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