svn commit: r191643 - in head/sys: kern sys

[Kostik Belousov]

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);
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/svn-src-all/attachments/20090429/31495e52/attachment.pgp