Messages in this thread | | | Subject | Re: hackbench regression with kernel 2.6.32-rc1 | From | "Zhang, Yanmin" <> | Date | Tue, 27 Oct 2009 16:03:04 +0800 |
| |
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/
| |