lkml.org 
[lkml]   [2009]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: hackbench regression with kernel 2.6.32-rc1
From
Date
On Fri, 2009-10-16 at 13:06 +0200, Mike Galbraith wrote:
> On Tue, 2009-10-13 at 11:12 +0800, Zhang, Yanmin wrote:
>
> > NEXT_BUDDY has no help on volanoMark and tbench.
>
> Can you try the patch below please? It does tries to preserve buddy
> affinity where possible, and mitigates over-preemption by strengthening
> buddies a bit. It improves vmark here by ~7%.
I ran some benchmarks against 2.6.32-rc1+Peter_2_patches+below_patch.
Below result is against 2.6.32-rc1.
hackbench result has about 10% improvement on stoakley (2*4 cores) and
tigerton (4*4 cores).
tbench still has about 5% regression on stoakley and tigerton.
VolanoMark has 33% regression on tigerton, but has 2% improvement on stoakley.

I also ran the benchmarks against the latest tips/master and got the similiar
results like above testing.

The testing against tips on Nehalem machine didn't show much improvement/regression.

>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 00f9e71..fb025d4 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -2007,8 +2007,12 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
>
> /*
> * Buddy candidates are cache hot:
> + *
> + * Do not honor buddies if there may be nothing else to
> + * prevent us from becoming idle.
> */
> if (sched_feat(CACHE_HOT_BUDDY) &&
> + task_rq(p)->nr_running >= sched_nr_latency &&
> (&p->se == cfs_rq_of(&p->se)->next ||
> &p->se == cfs_rq_of(&p->se)->last))
> return 1;
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index c32c3e6..428bf55 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -863,18 +863,20 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
> struct sched_entity *se = __pick_next_entity(cfs_rq);
> struct sched_entity *buddy;
>
> - if (cfs_rq->next) {
> + if (cfs_rq->next && sched_feat(NEXT_BUDDY)) {
> buddy = cfs_rq->next;
> - cfs_rq->next = NULL;
> - if (wakeup_preempt_entity(buddy, se) < 1)
> + if (wakeup_preempt_entity(buddy, se) < 1) {
> + cfs_rq->next = NULL;
> return buddy;
> + }
> }
>
> - if (cfs_rq->last) {
> + if (cfs_rq->last && sched_feat(LAST_BUDDY)) {
> buddy = cfs_rq->last;
> - cfs_rq->last = NULL;
> - if (wakeup_preempt_entity(buddy, se) < 1)
> + if (wakeup_preempt_entity(buddy, se) < 1) {
> + cfs_rq->last = NULL;
> return buddy;
> + }
> }
>
> return se;
> @@ -1600,9 +1602,9 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
> * Also, during early boot the idle thread is in the fair class, for
> * obvious reasons its a bad idea to schedule back to the idle thread.
> */
> - if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
> + if (!(wake_flags & WF_FORK) && likely(se->on_rq && curr != rq->idle))
> set_last_buddy(se);
> - if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
> + if (!(wake_flags & WF_FORK))
> set_next_buddy(pse);
>
> /*
>
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2009-10-27 09:05    [W:1.469 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site