svn commit: r191643 - in head/sys: kern sys
Andreas Tobler
andreast-list at fgznet.ch
Wed Apr 29 19:01:28 UTC 2009
Kostik Belousov wrote:
> On Wed, Apr 29, 2009 at 03:15:44AM +0000, Jeff Roberson wrote:
>> Author: jeff
>> Date: Wed Apr 29 03:15:43 2009
>> New Revision: 191643
>> URL: http://svn.freebsd.org/changeset/base/191643
>>
>> Log:
>> - Remove the bogus idle thread state code. This may have a race in it
>> 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
>>
>> Modified:
>> head/sys/kern/sched_ule.c
>> head/sys/kern/subr_smp.c
>> head/sys/sys/smp.h
>
> Now I see a reason why it is better #ifdef SMP the code that uses CG_FLAG_*.
> Also, we should check for tdq_cg != NULL in one more place.
>
> See the patch below, instead of exposing CG_FLAG_* for !SMP configs.
>
> diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
> index 680572d..fe3a119 100644
> --- a/sys/kern/sched_ule.c
> +++ b/sys/kern/sched_ule.c
> @@ -891,6 +891,7 @@ tdq_move(struct tdq *from, struct tdq *to)
> return (1);
> }
>
> +#ifdef SMP
> /*
> * This tdq has idled. Try to steal a thread from another cpu and switch
> * to it.
> @@ -947,6 +948,7 @@ tdq_idled(struct tdq *tdq)
> spinlock_exit();
> return (1);
> }
> +#endif
>
> /*
> * Notify a remote cpu of new work. Sends an IPI if criteria are met.
> @@ -2525,7 +2527,9 @@ sched_idletd(void *dummy)
> struct thread *td;
> struct tdq *tdq;
> int switchcnt;
> +#ifdef SMP
> int i;
> +#endif
>
> mtx_assert(&Giant, MA_NOTOWNED);
> td = curthread;
> @@ -2543,7 +2547,9 @@ sched_idletd(void *dummy)
> * loops while on SMT machines as this simply steals
> * cycles from cores doing useful work.
> */
> - if ((tdq->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0 &&
> +#ifdef SMP
> + if (tdq->tdq_cg != NULL &&
> + (tdq->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0 &&
> switchcnt > sched_idlespinthresh) {
> for (i = 0; i < sched_idlespins; i++) {
> if (tdq->tdq_load)
> @@ -2551,6 +2557,7 @@ sched_idletd(void *dummy)
> cpu_spinwait();
> }
> }
> +#endif
> switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
> if (tdq->tdq_load == 0)
> cpu_idle(switchcnt > 1);
Fyi, with the above patch I can build amd64, sparc64 and powerpc kernel.
Andreas
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