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Code Issues Releases Activity

- Remove the bogus idle thread state code. This may have a race in it

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and it only optimized out an ipi or mwait in very few cases.
 - Skip the adaptive idle code when running on SMT or HTT cores.  This
   just wastes cpu time that could be used on a busy thread on the same
   core.
 - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive.  Re-use
   CG_FLAG_THREAD to mean SMT or HTT.

Sponsored by:   Nokia
This commit is contained in:
Jeff Roberson 2009-04-29 03:15:43 +00:00
parent 6aaa0b3cf1
commit 7b55ab0534
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=191643
3 changed files with 15 additions and 30 deletions
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40
sys/kern/sched_ule.c
View File

@ -36,7 +36,7 @@
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
__FBSDID("$FreeBSD$);
#include "opt_hwpmc_hooks.h"
#include "opt_kdtrace.h"
@ -213,7 +213,6 @@ struct tdq {
volatile int tdq_load; /* Aggregate load. */
int tdq_sysload; /* For loadavg, !ITHD load. */
int tdq_transferable; /* Transferable thread count. */
volatile int tdq_idlestate; /* State of the idle thread. */
short tdq_switchcnt; /* Switches this tick. */
short tdq_oldswitchcnt; /* Switches last tick. */
u_char tdq_lowpri; /* Lowest priority thread. */
@ -360,7 +359,6 @@ tdq_print(int cpu)
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("\tidle state: %d\n", tdq->tdq_idlestate);
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
printf("\tload transferable: %d\n", tdq->tdq_transferable);
@ -913,7 +911,7 @@ tdq_idled(struct tdq *tdq)
/* 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_HTT | CG_FLAG_THREAD)) == 0)
if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
thresh = steal_thresh;
else
thresh = 1;
@ -968,13 +966,6 @@ tdq_notify(struct tdq *tdq, struct thread *td)
if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
return;
if (TD_IS_IDLETHREAD(ctd)) {
/*
* If the idle thread is still 'running' it's probably
* waiting on us to release the tdq spinlock already. No
* need to ipi.
*/
if (tdq->tdq_idlestate == TDQ_RUNNING)
return;
/*
* If the MD code has an idle wakeup routine try that before
* falling back to IPI.
@ -2536,12 +2527,10 @@ sched_idletd(void *dummy)
int switchcnt;
int i;
mtx_assert(&Giant, MA_NOTOWNED);
td = curthread;
tdq = TDQ_SELF();
mtx_assert(&Giant, MA_NOTOWNED);
/* ULE relies on preemption for idle interruption. */
for (;;) {
tdq->tdq_idlestate = TDQ_RUNNING;
#ifdef SMP
if (tdq_idled(tdq) == 0)
continue;
@ -2550,26 +2539,21 @@ sched_idletd(void *dummy)
/*
* If we're switching very frequently, spin while checking
* for load rather than entering a low power state that
* requires an IPI.
* 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 (switchcnt > sched_idlespinthresh) {
if ((tdq->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0 &&
switchcnt > sched_idlespinthresh) {
for (i = 0; i < sched_idlespins; i++) {
if (tdq->tdq_load)
break;
cpu_spinwait();
}
}
/*
* We must set our state to IDLE before checking
* tdq_load for the last time to avoid a race with
* tdq_notify().
*/
if (tdq->tdq_load == 0) {
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
tdq->tdq_idlestate = TDQ_IDLE;
if (tdq->tdq_load == 0)
cpu_idle(switchcnt > 1);
}
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);
@ -2683,7 +2667,7 @@ sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
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_THREAD) != 0)
if ((cg->cg_flags & CG_FLAG_SMT) != 0)
sbuf_printf(sb, "<flag name=\"THREAD\">SMT group</flag>\n");
}
sbuf_printf(sb, "</flags>\n");

2
sys/kern/subr_smp.c
View File

@ -491,7 +491,7 @@ smp_topo(void)
case 7:
/* quad core with a shared l3, 8 threads sharing L2. */
top = smp_topo_2level(CG_SHARE_L3, 4, CG_SHARE_L2, 8,
CG_FLAG_THREAD);
CG_FLAG_SMT);
break;
default:
/* Default, ask the system what it wants. */

3
sys/sys/smp.h
View File

@ -54,7 +54,8 @@ struct cpu_group {
* Behavior modifiers for load balancing and affinity.
*/
#define CG_FLAG_HTT 0x01 /* Schedule the alternate core last. */
#define CG_FLAG_THREAD 0x02 /* New age htt, less crippled. */
#define CG_FLAG_SMT 0x02 /* New age htt, less crippled. */
#define CG_FLAG_THREAD (CG_FLAG_HTT | CG_FLAG_SMT) /* Any threading. */
/*
* Convenience routines for building topologies.