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05dc0eb204
freebsd/sys/kern/sched_ule.c
Jeff Roberson 05dc0eb204 - Restore historical sched_yield() behavior by changing sched_relinquish() 
to simply switch rather than lowering priority and switching.  This allows
   threads of equal priority to run but not lesser priority.

Discussed with:	davidxu
Reported by:	NIIMI Satoshi <sa2c@sa2c.net>
Approved by:	re
2007-10-08 23:45:24 +00:00

2691 lines
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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_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>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <machine/cpu.h>
#include <machine/smp.h>
#if !defined(__i386__) && !defined(__amd64__)
#error "This architecture is not currently compatible with ULE"
#endif
#define KTR_ULE 0
/*
* Thread scheduler specific section. All fields are protected
* by the thread lock.
*/
struct td_sched {
TAILQ_ENTRY(td_sched) ts_procq; /* Run queue. */
struct thread *ts_thread; /* Active associated thread. */
struct runq *ts_runq; /* Run-queue we're queued on. */
short ts_flags; /* TSF_* flags. */
u_char ts_rqindex; /* Run queue index. */
u_char ts_cpu; /* CPU that we have affinity for. */
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 */
/* The following variables are only used for pctcpu calculation */
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 SMP
int ts_rltick; /* Real last tick, for affinity. */
#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;
/*
* 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;
#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
/*
* 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 {
struct mtx *tdq_lock; /* Pointer to group lock. */
struct runq tdq_realtime; /* real-time run queue. */
struct runq tdq_timeshare; /* timeshare run queue. */
struct runq tdq_idle; /* Queue of IDLE threads. */
int tdq_load; /* Aggregate load. */
u_char tdq_idx; /* Current insert index. */
u_char tdq_ridx; /* Current removal index. */
#ifdef SMP
u_char tdq_lowpri; /* Lowest priority thread. */
int tdq_transferable; /* Transferable thread count. */
LIST_ENTRY(tdq) tdq_siblings; /* Next in tdq group. */
struct tdq_group *tdq_group; /* Our processor group. */
#else
int tdq_sysload; /* For loadavg, !ITHD load. */
#endif
} __aligned(64);
#ifdef SMP
/*
* tdq groups are groups of processors which can cheaply share threads. When
* one processor in the group goes idle it will check the runqs of the other
* processors in its group prior to halting and waiting for an interrupt.
* These groups are suitable for SMT (Symetric Multi-Threading) and not NUMA.
* In a numa environment we'd want an idle bitmap per group and a two tiered
* load balancer.
*/
struct tdq_group {
struct mtx tdg_lock; /* Protects all fields below. */
int tdg_cpus; /* Count of CPUs in this tdq group. */
cpumask_t tdg_cpumask; /* Mask of cpus in this group. */
cpumask_t tdg_idlemask; /* Idle cpus in this group. */
cpumask_t tdg_mask; /* Bit mask for first cpu. */
int tdg_load; /* Total load of this group. */
int tdg_transferable; /* Transferable load of this group. */
LIST_HEAD(, tdq) tdg_members; /* Linked list of all members. */
char tdg_name[16]; /* lock name. */
} __aligned(64);
#define SCHED_AFFINITY_DEFAULT (max(1, hz / 300))
#define SCHED_AFFINITY(ts) ((ts)->ts_rltick > ticks - affinity)
/*
* Run-time tunables.
*/
static int rebalance = 1;
static int balance_interval = 128; /* Default set in sched_initticks(). */
static int pick_pri = 1;
static int affinity;
static int tryself = 1;
static int steal_htt = 1;
static int steal_idle = 1;
static int steal_thresh = 2;
static int topology = 0;
/*
* One thread queue per processor.
*/
static volatile cpumask_t tdq_idle;
static int tdg_maxid;
static struct tdq tdq_cpu[MAXCPU];
static struct tdq_group tdq_groups[MAXCPU];
static struct tdq *balance_tdq;
static int balance_group_ticks;
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))
#define TDQ_GROUP(x) (&tdq_groups[(x)])
#define TDG_ID(x) ((int)((x) - tdq_groups))
#else /* !SMP */
static struct tdq tdq_cpu;
static struct mtx tdq_lock;
#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 td_sched * tdq_choose(struct tdq *);
static void tdq_setup(struct tdq *);
static void tdq_load_add(struct tdq *, struct td_sched *);
static void tdq_load_rem(struct tdq *, struct td_sched *);
static __inline void tdq_runq_add(struct tdq *, struct td_sched *, int);
static __inline void tdq_runq_rem(struct tdq *, struct td_sched *);
void tdq_print(int cpu);
static void runq_print(struct runq *rq);
static void tdq_add(struct tdq *, struct thread *, int);
#ifdef SMP
static void tdq_move(struct tdq *, struct tdq *);
static int tdq_idled(struct tdq *);
static void tdq_notify(struct td_sched *);
static struct td_sched *tdq_steal(struct tdq *);
static struct td_sched *runq_steal(struct runq *);
static int sched_pickcpu(struct td_sched *, int);
static void sched_balance(void);
static void sched_balance_groups(void);
static void sched_balance_group(struct tdq_group *);
static void sched_balance_pair(struct tdq *, struct tdq *);
static inline struct tdq *sched_setcpu(struct td_sched *, 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);
#define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
#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 td_sched *ts;
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(ts, rqh, ts_procq) {
printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
ts->ts_thread, ts->ts_thread->td_proc->p_comm, ts->ts_thread->td_priority, ts->ts_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("\tlockptr %p\n", TDQ_LOCKPTR(tdq));
printf("\tload: %d\n", tdq->tdq_load);
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
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);
#ifdef SMP
printf("\tload transferable: %d\n", tdq->tdq_transferable);
printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
printf("\tgroup: %d\n", TDG_ID(tdq->tdq_group));
printf("\tLock name: %s\n", tdq->tdq_group->tdg_name);
#endif
}
#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 td_sched *ts, int flags)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
#ifdef SMP
if (THREAD_CAN_MIGRATE(ts->ts_thread)) {
tdq->tdq_transferable++;
tdq->tdq_group->tdg_transferable++;
ts->ts_flags |= TSF_XFERABLE;
}
#endif
if (ts->ts_runq == &tdq->tdq_timeshare) {
u_char pri;
pri = ts->ts_thread->td_priority;
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, ts, pri, flags);
} else
runq_add(ts->ts_runq, ts, 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 td_sched *ts)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(ts->ts_runq != NULL,
("tdq_runq_remove: thread %p null ts_runq", ts->ts_thread));
#ifdef SMP
if (ts->ts_flags & TSF_XFERABLE) {
tdq->tdq_transferable--;
tdq->tdq_group->tdg_transferable--;
ts->ts_flags &= ~TSF_XFERABLE;
}
#endif
if (ts->ts_runq == &tdq->tdq_timeshare) {
if (tdq->tdq_idx != tdq->tdq_ridx)
runq_remove_idx(ts->ts_runq, ts, &tdq->tdq_ridx);
else
runq_remove_idx(ts->ts_runq, ts, NULL);
/*
* For timeshare threads we update the priority here so
* the priority reflects the time we've been sleeping.
*/
ts->ts_ltick = ticks;
sched_pctcpu_update(ts);
sched_priority(ts->ts_thread);
} else
runq_remove(ts->ts_runq, ts);
}
/*
* 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 td_sched *ts)
{
int class;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
class = PRI_BASE(ts->ts_thread->td_pri_class);
tdq->tdq_load++;
CTR2(KTR_SCHED, "cpu %d load: %d", TDQ_ID(tdq), tdq->tdq_load);
if (class != PRI_ITHD &&
(ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
tdq->tdq_group->tdg_load++;
#else
tdq->tdq_sysload++;
#endif
}
/*
* Remove the load from a thread that is transitioning to a sleep state or
* exiting.
*/
static void
tdq_load_rem(struct tdq *tdq, struct td_sched *ts)
{
int class;
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
class = PRI_BASE(ts->ts_thread->td_pri_class);
if (class != PRI_ITHD &&
(ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
tdq->tdq_group->tdg_load--;
#else
tdq->tdq_sysload--;
#endif
KASSERT(tdq->tdq_load != 0,
("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
tdq->tdq_load--;
CTR1(KTR_SCHED, "load: %d", tdq->tdq_load);
ts->ts_runq = NULL;
}
#ifdef SMP
/*
* sched_balance is a simple CPU load balancing algorithm. It operates by
* finding the least loaded and most loaded cpu and equalizing their load
* by migrating some processes.
*
* Dealing only with two CPUs at a time has two advantages. Firstly, most
* installations will only have 2 cpus. Secondly, load balancing too much at
* once can have an unpleasant effect on the system. The scheduler rarely has
* enough information to make perfect decisions. So this algorithm chooses
* simplicity and more gradual effects on load in larger systems.
*
*/
static void
sched_balance()
{
struct tdq_group *high;
struct tdq_group *low;
struct tdq_group *tdg;
struct tdq *tdq;
int cnt;
int i;
/*
* 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);
low = high = NULL;
i = random() % (tdg_maxid + 1);
for (cnt = 0; cnt <= tdg_maxid; cnt++) {
tdg = TDQ_GROUP(i);
/*
* Find the CPU with the highest load that has some
* threads to transfer.
*/
if ((high == NULL || tdg->tdg_load > high->tdg_load)
&& tdg->tdg_transferable)
high = tdg;
if (low == NULL || tdg->tdg_load < low->tdg_load)
low = tdg;
if (++i > tdg_maxid)
i = 0;
}
if (low != NULL && high != NULL && high != low)
sched_balance_pair(LIST_FIRST(&high->tdg_members),
LIST_FIRST(&low->tdg_members));
TDQ_LOCK(tdq);
}
/*
* Balance load between CPUs in a group. Will only migrate within the group.
*/
static void
sched_balance_groups()
{
struct tdq *tdq;
int i;
/*
* Select a random time between .5 * balance_interval and
* 1.5 * balance_interval.
*/
balance_group_ticks = max(balance_interval / 2, 1);
balance_group_ticks += random() % balance_interval;
if (smp_started == 0 || rebalance == 0)
return;
tdq = TDQ_SELF();
TDQ_UNLOCK(tdq);
for (i = 0; i <= tdg_maxid; i++)
sched_balance_group(TDQ_GROUP(i));
TDQ_LOCK(tdq);
}
/*
* Finds the greatest imbalance between two tdqs in a group.
*/
static void
sched_balance_group(struct tdq_group *tdg)
{
struct tdq *tdq;
struct tdq *high;
struct tdq *low;
int load;
if (tdg->tdg_transferable == 0)
return;
low = NULL;
high = NULL;
LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
load = tdq->tdq_load;
if (high == NULL || load > high->tdq_load)
high = tdq;
if (low == NULL || load < low->tdq_load)
low = tdq;
}
if (high != NULL && low != NULL && high != low)
sched_balance_pair(high, low);
}
/*
* 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 void
sched_balance_pair(struct tdq *high, struct tdq *low)
{
int transferable;
int high_load;
int low_load;
int move;
int diff;
int i;
tdq_lock_pair(high, low);
/*
* If we're transfering within a group we have to use this specific
* tdq's transferable count, otherwise we can steal from other members
* of the group.
*/
if (high->tdq_group == low->tdq_group) {
transferable = high->tdq_transferable;
high_load = high->tdq_load;
low_load = low->tdq_load;
} else {
transferable = high->tdq_group->tdg_transferable;
high_load = high->tdq_group->tdg_load;
low_load = low->tdq_group->tdg_load;
}
/*
* 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++)
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;
}
/*
* Move a thread from one thread queue to another.
*/
static void
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);
ts = tdq_steal(tdq);
if (ts == NULL) {
struct tdq_group *tdg;
tdg = tdq->tdq_group;
LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
if (tdq == from || tdq->tdq_transferable == 0)
continue;
ts = tdq_steal(tdq);
break;
}
if (ts == NULL)
return;
}
if (tdq == to)
return;
td = ts->ts_thread;
/*
* 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);
}
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
*/
static int
tdq_idled(struct tdq *tdq)
{
struct tdq_group *tdg;
struct tdq *steal;
int highload;
int highcpu;
int load;
int cpu;
/* We don't want to be preempted while we're iterating over tdqs */
spinlock_enter();
tdg = tdq->tdq_group;
/*
* If we're in a cpu group, try and steal threads from another cpu in
* the group before idling. In a HTT group all cpus share the same
* run-queue lock, however, we still need a recursive lock to
* call tdq_move().
*/
if (steal_htt && tdg->tdg_cpus > 1 && tdg->tdg_transferable) {
TDQ_LOCK(tdq);
LIST_FOREACH(steal, &tdg->tdg_members, tdq_siblings) {
if (steal == tdq || steal->tdq_transferable == 0)
continue;
TDQ_LOCK(steal);
goto steal;
}
TDQ_UNLOCK(tdq);
}
for (;;) {
if (steal_idle == 0)
break;
highcpu = 0;
highload = 0;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
steal = TDQ_CPU(cpu);
load = TDQ_CPU(cpu)->tdq_transferable;
if (load < highload)
continue;
highload = load;
highcpu = cpu;
}
if (highload < steal_thresh)
break;
steal = TDQ_CPU(highcpu);
tdq_lock_pair(tdq, steal);
if (steal->tdq_transferable >= steal_thresh)
goto steal;
tdq_unlock_pair(tdq, steal);
break;
}
spinlock_exit();
return (1);
steal:
spinlock_exit();
tdq_move(steal, tdq);
TDQ_UNLOCK(steal);
mi_switch(SW_VOL, NULL);
thread_unlock(curthread);
return (0);
}
/*
* Notify a remote cpu of new work. Sends an IPI if criteria are met.
*/
static void
tdq_notify(struct td_sched *ts)
{
struct thread *ctd;
struct pcpu *pcpu;
int cpri;
int pri;
int cpu;
cpu = ts->ts_cpu;
pri = ts->ts_thread->td_priority;
pcpu = pcpu_find(cpu);
ctd = pcpu->pc_curthread;
cpri = ctd->td_priority;
/*
* If our priority is not better than the current priority there is
* nothing to do.
*/
if (pri > cpri)
return;
/*
* Always IPI idle.
*/
if (cpri > PRI_MIN_IDLE)
goto sendipi;
/*
* If we're realtime or better and there is timeshare or worse running
* send an IPI.
*/
if (pri < PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
goto sendipi;
/*
* Otherwise only IPI if we exceed the threshold.
*/
if (pri > preempt_thresh)
return;
sendipi:
ctd->td_flags |= TDF_NEEDRESCHED;
ipi_selected(1 << cpu, IPI_PREEMPT);
}
/*
* Steals load from a timeshare queue. Honors the rotating queue head
* index.
*/
static struct td_sched *
runq_steal_from(struct runq *rq, u_char start)
{
struct td_sched *ts;
struct rqbits *rqb;
struct rqhead *rqh;
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(ts, rqh, ts_procq) {
if (first && THREAD_CAN_MIGRATE(ts->ts_thread))
return (ts);
first = 1;
}
}
if (start != 0) {
start = 0;
goto again;
}
return (NULL);
}
/*
* Steals load from a standard linear queue.
*/
static struct td_sched *
runq_steal(struct runq *rq)
{
struct rqhead *rqh;
struct rqbits *rqb;
struct td_sched *ts;
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(ts, rqh, ts_procq)
if (THREAD_CAN_MIGRATE(ts->ts_thread))
return (ts);
}
}
return (NULL);
}
/*
* Attempt to steal a thread in priority order from a thread queue.
*/
static struct td_sched *
tdq_steal(struct tdq *tdq)
{
struct td_sched *ts;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
if ((ts = runq_steal(&tdq->tdq_realtime)) != NULL)
return (ts);
if ((ts = runq_steal_from(&tdq->tdq_timeshare, tdq->tdq_ridx)) != NULL)
return (ts);
return (runq_steal(&tdq->tdq_idle));
}
/*
* 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 td_sched *ts, int cpu, int flags)
{
struct thread *td;
struct tdq *tdq;
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
tdq = TDQ_CPU(cpu);
td = ts->ts_thread;
ts->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);
}
/*
* Find the thread queue running the lowest priority thread.
*/
static int
tdq_lowestpri(void)
{
struct tdq *tdq;
int lowpri;
int lowcpu;
int lowload;
int load;
int cpu;
int pri;
lowload = 0;
lowpri = lowcpu = 0;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
tdq = TDQ_CPU(cpu);
pri = tdq->tdq_lowpri;
load = TDQ_CPU(cpu)->tdq_load;
CTR4(KTR_ULE,
"cpu %d pri %d lowcpu %d lowpri %d",
cpu, pri, lowcpu, lowpri);
if (pri < lowpri)
continue;
if (lowpri && lowpri == pri && load > lowload)
continue;
lowpri = pri;
lowcpu = cpu;
lowload = load;
}
return (lowcpu);
}
/*
* Find the thread queue with the least load.
*/
static int
tdq_lowestload(void)
{
struct tdq *tdq;
int lowload;
int lowpri;
int lowcpu;
int load;
int cpu;
int pri;
lowcpu = 0;
lowload = TDQ_CPU(0)->tdq_load;
lowpri = TDQ_CPU(0)->tdq_lowpri;
for (cpu = 1; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load;
pri = tdq->tdq_lowpri;
CTR4(KTR_ULE, "cpu %d load %d lowcpu %d lowload %d",
cpu, load, lowcpu, lowload);
if (load > lowload)
continue;
if (load == lowload && pri < lowpri)
continue;
lowcpu = cpu;
lowload = load;
lowpri = pri;
}
return (lowcpu);
}
/*
* Pick the destination cpu for sched_add(). Respects affinity and makes
* a determination based on load or priority of available processors.
*/
static int
sched_pickcpu(struct td_sched *ts, int flags)
{
struct tdq *tdq;
int self;
int pri;
int cpu;
cpu = self = PCPU_GET(cpuid);
if (smp_started == 0)
return (self);
/*
* Don't migrate a running thread from sched_switch().
*/
if (flags & SRQ_OURSELF) {
CTR1(KTR_ULE, "YIELDING %d",
curthread->td_priority);
return (self);
}
pri = ts->ts_thread->td_priority;
cpu = ts->ts_cpu;
/*
* Regardless of affinity, if the last cpu is idle send it there.
*/
tdq = TDQ_CPU(cpu);
if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
CTR5(KTR_ULE,
"ts_cpu %d idle, ltick %d ticks %d pri %d curthread %d",
ts->ts_cpu, ts->ts_rltick, ticks, pri,
tdq->tdq_lowpri);
return (ts->ts_cpu);
}
/*
* If we have affinity, try to place it on the cpu we last ran on.
*/
if (SCHED_AFFINITY(ts) && tdq->tdq_lowpri > pri) {
CTR5(KTR_ULE,
"affinity for %d, ltick %d ticks %d pri %d curthread %d",
ts->ts_cpu, ts->ts_rltick, ticks, pri,
tdq->tdq_lowpri);
return (ts->ts_cpu);
}
/*
* Look for an idle group.
*/
CTR1(KTR_ULE, "tdq_idle %X", tdq_idle);
cpu = ffs(tdq_idle);
if (cpu)
return (--cpu);
/*
* If there are no idle cores see if we can run the thread locally.
* This may improve locality among sleepers and wakers when there
* is shared data.
*/
if (tryself && pri < curthread->td_priority) {
CTR1(KTR_ULE, "tryself %d",
curthread->td_priority);
return (self);
}
/*
* Now search for the cpu running the lowest priority thread with
* the least load.
*/
if (pick_pri)
cpu = tdq_lowestpri();
else
cpu = tdq_lowestload();
return (cpu);
}
#endif /* SMP */
/*
* Pick the highest priority task we have and return it.
*/
static struct td_sched *
tdq_choose(struct tdq *tdq)
{
struct td_sched *ts;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
ts = runq_choose(&tdq->tdq_realtime);
if (ts != NULL)
return (ts);
ts = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
if (ts != NULL) {
KASSERT(ts->ts_thread->td_priority >= PRI_MIN_TIMESHARE,
("tdq_choose: Invalid priority on timeshare queue %d",
ts->ts_thread->td_priority));
return (ts);
}
ts = runq_choose(&tdq->tdq_idle);
if (ts != NULL) {
KASSERT(ts->ts_thread->td_priority >= PRI_MIN_IDLE,
("tdq_choose: Invalid priority on idle queue %d",
ts->ts_thread->td_priority));
return (ts);
}
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);
tdq->tdq_load = 0;
}
#ifdef SMP
static void
tdg_setup(struct tdq_group *tdg)
{
if (bootverbose)
printf("ULE: setup cpu group %d\n", TDG_ID(tdg));
snprintf(tdg->tdg_name, sizeof(tdg->tdg_name),
"sched lock %d", (int)TDG_ID(tdg));
mtx_init(&tdg->tdg_lock, tdg->tdg_name, "sched lock",
MTX_SPIN | MTX_RECURSE);
LIST_INIT(&tdg->tdg_members);
tdg->tdg_load = 0;
tdg->tdg_transferable = 0;
tdg->tdg_cpus = 0;
tdg->tdg_mask = 0;
tdg->tdg_cpumask = 0;
tdg->tdg_idlemask = 0;
}
static void
tdg_add(struct tdq_group *tdg, struct tdq *tdq)
{
if (tdg->tdg_mask == 0)
tdg->tdg_mask |= 1 << TDQ_ID(tdq);
tdg->tdg_cpumask |= 1 << TDQ_ID(tdq);
tdg->tdg_cpus++;
tdq->tdq_group = tdg;
tdq->tdq_lock = &tdg->tdg_lock;
LIST_INSERT_HEAD(&tdg->tdg_members, tdq, tdq_siblings);
if (bootverbose)
printf("ULE: adding cpu %d to group %d: cpus %d mask 0x%X\n",
TDQ_ID(tdq), TDG_ID(tdg), tdg->tdg_cpus, tdg->tdg_cpumask);
}
static void
sched_setup_topology(void)
{
struct tdq_group *tdg;
struct cpu_group *cg;
int balance_groups;
struct tdq *tdq;
int i;
int j;
topology = 1;
balance_groups = 0;
for (i = 0; i < smp_topology->ct_count; i++) {
cg = &smp_topology->ct_group[i];
tdg = &tdq_groups[i];
/*
* Initialize the group.
*/
tdg_setup(tdg);
/*
* Find all of the group members and add them.
*/
for (j = 0; j < MAXCPU; j++) {
if ((cg->cg_mask & (1 << j)) != 0) {
tdq = TDQ_CPU(j);
tdq_setup(tdq);
tdg_add(tdg, tdq);
}
}
if (tdg->tdg_cpus > 1)
balance_groups = 1;
}
tdg_maxid = smp_topology->ct_count - 1;
if (balance_groups)
sched_balance_groups();
}
static void
sched_setup_smp(void)
{
struct tdq_group *tdg;
struct tdq *tdq;
int cpus;
int i;
for (cpus = 0, i = 0; i < MAXCPU; i++) {
if (CPU_ABSENT(i))
continue;
tdq = &tdq_cpu[i];
tdg = &tdq_groups[i];
/*
* Setup a tdq group with one member.
*/
tdg_setup(tdg);
tdq_setup(tdq);
tdg_add(tdg, tdq);
cpus++;
}
tdg_maxid = cpus - 1;
}
/*
* Fake a topology with one group containing all CPUs.
*/
static void
sched_fake_topo(void)
{
#ifdef SCHED_FAKE_TOPOLOGY
static struct cpu_top top;
static struct cpu_group group;
top.ct_count = 1;
top.ct_group = &group;
group.cg_mask = all_cpus;
group.cg_count = mp_ncpus;
group.cg_children = 0;
smp_topology = &top;
#endif
}
#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_fake_topo();
/*
* Setup tdqs based on a topology configuration or vanilla SMP based
* on mp_maxid.
*/
if (smp_topology == NULL)
sched_setup_smp();
else
sched_setup_topology();
balance_tdq = tdq;
sched_balance();
#else
tdq_setup(tdq);
mtx_init(&tdq_lock, "sched lock", "sched lock", MTX_SPIN | MTX_RECURSE);
tdq->tdq_lock = &tdq_lock;
#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, &td_sched0);
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 log2(mp_ncpu) but no greater than 4. This
* prevents excess thrashing on large machines and excess idle on
* smaller machines.
*/
steal_thresh = min(ffs(mp_ncpus) - 1, 4);
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_thread = &thread0;
}
/*
* 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;
CTR6(KTR_SCHED, "sched_prio: %p(%s) prio %d newprio %d by %p(%s)",
td, td->td_proc->p_comm, td->td_priority, prio, curthread,
curthread->td_proc->p_comm);
ts = td->td_sched;
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_priority == prio)
return;
if (TD_ON_RUNQ(td) && prio < td->td_priority) {
/*
* 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.
*/
sched_rem(td);
td->td_priority = prio;
sched_add(td, SRQ_BORROWING);
} else {
#ifdef SMP
struct tdq *tdq;
tdq = TDQ_CPU(ts->ts_cpu);
if (prio < tdq->tdq_lowpri)
tdq->tdq_lowpri = prio;
#endif
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;
if (TD_ON_UPILOCK(td) && oldprio != prio)
umtx_pi_adjust(td, oldprio);
}
void
sched_lend_user_prio(struct thread *td, u_char prio)
{
u_char oldprio;
td->td_flags |= TDF_UBORROWING;
oldprio = td->td_user_pri;
td->td_user_pri = prio;
if (TD_ON_UPILOCK(td) && oldprio != prio)
umtx_pi_adjust(td, oldprio);
}
void
sched_unlend_user_prio(struct thread *td, u_char prio)
{
u_char base_pri;
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);
}
/*
* Add the thread passed as 'newtd' to the run queue before selecting
* the next thread to run. This is only used for KSE.
*/
static void
sched_switchin(struct tdq *tdq, struct thread *td)
{
#ifdef SMP
spinlock_enter();
TDQ_UNLOCK(tdq);
thread_lock(td);
spinlock_exit();
sched_setcpu(td->td_sched, TDQ_ID(tdq), SRQ_YIELDING);
#else
td->td_lock = TDQ_LOCKPTR(tdq);
#endif
tdq_add(tdq, td, SRQ_YIELDING);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
}
/*
* 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
/*
* 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. */
TDQ_LOCK(tdn);
tdq_add(tdn, td, flags);
tdq_notify(td->td_sched);
/*
* After we unlock tdn the new cpu still can't switch into this
* thread until we've unblocked it in cpu_switch(). The lock
* pointers may match in the case of HTT cores. Don't unlock here
* or we can deadlock when the other CPU runs the IPI handler.
*/
if (TDQ_LOCKPTR(tdn) != TDQ_LOCKPTR(tdq)) {
TDQ_UNLOCK(tdn);
TDQ_LOCK(tdq);
}
spinlock_exit();
#endif
return (TDQ_LOCKPTR(tdn));
}
/*
* 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);
}
/*
* 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);
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
ts = td->td_sched;
mtx = td->td_lock;
#ifdef SMP
ts->ts_rltick = ticks;
if (newtd && newtd->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = newtd->td_priority;
#endif
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
td->td_flags &= ~TDF_NEEDRESCHED;
td->td_owepreempt = 0;
/*
* 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));
tdq_load_rem(tdq, ts);
srqflag = (flags & SW_PREEMPT) ?
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
SRQ_OURSELF|SRQ_YIELDING;
if (ts->ts_cpu == cpuid)
tdq_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, ts);
}
/*
* 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);
/*
* If KSE assigned a new thread just add it here and let choosethread
* select the best one.
*/
if (newtd != NULL)
sched_switchin(tdq, newtd);
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
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
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);
#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.
*/
#ifdef SMP
/* We should always get here with the lowest priority td possible */
tdq->tdq_lowpri = td->td_priority;
#endif
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);
PROC_SLOCK_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)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_slptick = ticks;
}
/*
* 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;
/*
* 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);
sched_priority(td);
}
/* 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;
/*
* Initialize child.
*/
THREAD_LOCK_ASSERT(td, MA_OWNED);
sched_newthread(child);
child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
ts = td->td_sched;
ts2 = child->td_sched;
ts2->ts_cpu = ts->ts_cpu;
ts2->ts_runq = NULL;
/*
* 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. */
}
/*
* 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;
#ifdef SMP
/*
* On SMP if we're on the RUNQ we must adjust the transferable
* count because could be changing to or from an interrupt
* class.
*/
if (TD_ON_RUNQ(td)) {
struct tdq *tdq;
tdq = TDQ_CPU(td->td_sched->ts_cpu);
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable--;
tdq->tdq_group->tdg_transferable--;
}
td->td_pri_class = class;
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable++;
tdq->tdq_group->tdg_transferable++;
}
}
#endif
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;
CTR3(KTR_SCHED, "sched_exit: %p(%s) prio %d",
child, child->td_proc->p_comm, child->td_priority);
PROC_SLOCK_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)
{
CTR3(KTR_SCHED, "sched_exit_thread: %p(%s) prio %d",
child, child->td_proc->p_comm, child->td_priority);
#ifdef KSE
/*
* KSE forks and exits so often that this penalty causes short-lived
* threads to always be non-interactive. This causes mozilla to
* crawl under load.
*/
if ((td->td_pflags & TDP_SA) && td->td_proc == child->td_proc)
return;
#endif
/*
* 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);
}
/*
* 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;
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();
if (balance_group_ticks && --balance_group_ticks == 0)
sched_balance_groups();
}
#endif
/*
* 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;
/*
* We only do slicing code for TIMESHARE threads.
*/
if (td->td_pri_class != PRI_TIMESHARE)
return;
/*
* 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);
/*
* We used up one time slice.
*/
if (--ts->ts_slice > 0)
return;
/*
* We're out of time, recompute priorities and requeue.
*/
sched_priority(td);
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;
/* 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)
{
#ifdef SMP
struct tdq_group *tdg;
#endif
struct td_sched *ts;
struct tdq *tdq;
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
ts = tdq_choose(tdq);
if (ts) {
tdq_runq_rem(tdq, ts);
return (ts->ts_thread);
}
#ifdef SMP
/*
* We only set the idled bit when all of the cpus in the group are
* idle. Otherwise we could get into a situation where a thread bounces
* back and forth between two idle cores on seperate physical CPUs.
*/
tdg = tdq->tdq_group;
tdg->tdg_idlemask |= PCPU_GET(cpumask);
if (tdg->tdg_idlemask == tdg->tdg_cpumask)
atomic_set_int(&tdq_idle, tdg->tdg_mask);
tdq->tdq_lowpri = PRI_MAX_IDLE;
#endif
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;
ctd = curthread;
pri = td->td_priority;
cpri = ctd->td_priority;
if (td->td_priority < ctd->td_priority)
curthread->td_flags |= TDF_NEEDRESCHED;
if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
return;
/*
* Always preempt IDLE threads. Otherwise only if the preempting
* thread is an ithread.
*/
if (pri > preempt_thresh && cpri < PRI_MIN_IDLE)
return;
ctd->td_owepreempt = 1;
return;
}
/*
* Add a thread to a thread queue. Initializes priority, slice, runq, and
* add it to the appropriate queue. This is the internal function called
* when the tdq is predetermined.
*/
void
tdq_add(struct tdq *tdq, struct thread *td, int flags)
{
struct td_sched *ts;
int class;
#ifdef SMP
int cpumask;
#endif
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"));
ts = td->td_sched;
class = PRI_BASE(td->td_pri_class);
TD_SET_RUNQ(td);
if (ts->ts_slice == 0)
ts->ts_slice = sched_slice;
/*
* Pick the run queue based on priority.
*/
if (td->td_priority <= PRI_MAX_REALTIME)
ts->ts_runq = &tdq->tdq_realtime;
else if (td->td_priority <= PRI_MAX_TIMESHARE)
ts->ts_runq = &tdq->tdq_timeshare;
else
ts->ts_runq = &tdq->tdq_idle;
#ifdef SMP
cpumask = 1 << ts->ts_cpu;
/*
* If we had been idle, clear our bit in the group and potentially
* the global bitmap.
*/
if ((class != PRI_IDLE && class != PRI_ITHD) &&
(tdq->tdq_group->tdg_idlemask & cpumask) != 0) {
/*
* Check to see if our group is unidling, and if so, remove it
* from the global idle mask.
*/
if (tdq->tdq_group->tdg_idlemask ==
tdq->tdq_group->tdg_cpumask)
atomic_clear_int(&tdq_idle, tdq->tdq_group->tdg_mask);
/*
* Now remove ourselves from the group specific idle mask.
*/
tdq->tdq_group->tdg_idlemask &= ~cpumask;
}
if (td->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = td->td_priority;
#endif
tdq_runq_add(tdq, ts, flags);
tdq_load_add(tdq, ts);
}
/*
* 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 td_sched *ts;
struct tdq *tdq;
#ifdef SMP
int cpuid;
int cpu;
#endif
CTR5(KTR_SCHED, "sched_add: %p(%s) prio %d by %p(%s)",
td, td->td_proc->p_comm, td->td_priority, curthread,
curthread->td_proc->p_comm);
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
/*
* 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
cpuid = PCPU_GET(cpuid);
/*
* Pick the destination cpu and if it isn't ours transfer to the
* target cpu.
*/
if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_MIGRATE(td))
cpu = cpuid;
else if (!THREAD_CAN_MIGRATE(td))
cpu = ts->ts_cpu;
else
cpu = sched_pickcpu(ts, flags);
tdq = sched_setcpu(ts, cpu, flags);
tdq_add(tdq, td, flags);
if (cpu != cpuid) {
tdq_notify(ts);
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;
struct td_sched *ts;
CTR5(KTR_SCHED, "sched_rem: %p(%s) prio %d by %p(%s)",
td, td->td_proc->p_comm, td->td_priority, curthread,
curthread->td_proc->p_comm);
ts = td->td_sched;
tdq = TDQ_CPU(ts->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, ts);
tdq_load_rem(tdq, ts);
TD_SET_CAN_RUN(td);
}
/*
* 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);
}
/*
* 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;
#ifdef SMP
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);
#endif
}
/*
* 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;
#ifdef SMP
sched_unpin();
#endif
}
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);
SCHED_STAT_INC(switch_relinquish);
mi_switch(SW_VOL, 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 <= tdg_maxid; i++)
total += TDQ_GROUP(i)->tdg_load;
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));
}
/*
* The actual idle process.
*/
void
sched_idletd(void *dummy)
{
struct thread *td;
struct tdq *tdq;
td = curthread;
tdq = TDQ_SELF();
mtx_assert(&Giant, MA_NOTOWNED);
/* ULE relies on preemption for idle interruption. */
for (;;) {
#ifdef SMP
if (tdq_idled(tdq))
cpu_idle();
#else
cpu_idle();
#endif
}
}
/*
* 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->td_sched);
}
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);
}
static 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");
#ifdef SMP
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri, CTLFLAG_RW, &pick_pri, 0,
"Pick the target cpu based on priority rather than load.");
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, tryself, CTLFLAG_RW, &tryself, 0, "");
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");
SYSCTL_INT(_kern_sched, OID_AUTO, topology, CTLFLAG_RD, &topology, 0,
"True when a topology has been specified by the MD code.");
#endif
/* ps compat. All cpu percentages from ULE are weighted. */
static int ccpu = 0;
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
#define KERN_SWITCH_INCLUDE 1
#include "kern/kern_switch.c"
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