Messages in this thread Patch in this message | | | Date | Thu, 30 Jul 2009 11:01:49 -0400 | From | Gregory Haskins <> | Subject | Re: [PATCH 1/2] [RESEND] sched: Fully integrate cpus_active_map and root-domain code |
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Gregory Haskins wrote: > (Applies to 2.6.31-rc4) > > [ > This patch was originaly sent about a year ago, but got dropped > presumably by accident. Here is the original thread. > > http://lkml.org/lkml/2008/7/22/281 > > At that time, Peter and Max acked it. It has now been forward > ported to the new cpumask interface. I will be so bold as to > carry their acks forward since the basic logic is the same. > However, a new acknowledgement, if they have the time to review, > would be ideal. > > I have tested this patch on a 4-way system using Max's recommended > "echo 0|1 > cpu1/online" technique and it appears to work properly > ] > > What: Reflect "active" cpus in the rq->rd->online field, instead of the > online_map. > > Motivation: Things that use the root-domain code (such as cpupri) only > care about cpus classified as "active" anyway. By synchronizing the > root-domain state with the active map, we allow several optimizations. > > For instance, we can remove an extra cpumask_and from the scheduler > hotpath by utilizing rq->rd->online (since it is now a cached version > of cpu_active_map & rq->rd->span). > > Signed-off-by: Gregory Haskins <ghaskins@novell.com> > Acked-by: Peter Zijlstra <peterz@infradead.org> > Acked-by: Max Krasnyansky <maxk@qualcomm.com> > --- > > kernel/sched.c | 2 +- > kernel/sched_fair.c | 10 +++++++--- > kernel/sched_rt.c | 7 ------- > 3 files changed, 8 insertions(+), 11 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 1a104e6..38a1526 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -7874,7 +7874,7 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd) > rq->rd = rd; > > cpumask_set_cpu(rq->cpu, rd->span); > - if (cpumask_test_cpu(rq->cpu, cpu_online_mask)) > + if (cpumask_test_cpu(rq->cpu, cpu_active_mask)) > set_rq_online(rq); > > spin_unlock_irqrestore(&rq->lock, flags); > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 9ffb2b2..2b9cae6 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1040,17 +1040,21 @@ static void yield_task_fair(struct rq *rq) > * search starts with cpus closest then further out as needed, > * so we always favor a closer, idle cpu. > * Domains may include CPUs that are not usable for migration, > - * hence we need to mask them out (cpu_active_mask) > + * hence we need to mask them out (rq->rd->online) > * > * Returns the CPU we should wake onto. > */ > #if defined(ARCH_HAS_SCHED_WAKE_IDLE) > + > +#define cpu_rd_active(cpu, rq) cpumask_test_cpu(cpu, rq->rd->online) > + > static int wake_idle(int cpu, struct task_struct *p) > { > struct sched_domain *sd; > int i; > unsigned int chosen_wakeup_cpu; > int this_cpu; > + struct rq *task_rq = task_rq(p); > > /* > * At POWERSAVINGS_BALANCE_WAKEUP level, if both this_cpu and prev_cpu > @@ -1083,10 +1087,10 @@ static int wake_idle(int cpu, struct task_struct *p) > for_each_domain(cpu, sd) { > if ((sd->flags & SD_WAKE_IDLE) > || ((sd->flags & SD_WAKE_IDLE_FAR) > - && !task_hot(p, task_rq(p)->clock, sd))) { > + && !task_hot(p, task_rq->clock, sd))) { > for_each_cpu_and(i, sched_domain_span(sd), > &p->cpus_allowed) {
Hmm, something got suboptimal in translation from the original patch.
This would be better expressed as:
for_each_cpu_and(i, rq->rd->online, &p->cpus_allowed) { if (idle_cpu(i)... }
> - if (cpu_active(i) && idle_cpu(i)) { > + if (cpu_rd_active(i, task_rq) && idle_cpu(i)) { > if (i != task_cpu(p)) { > schedstat_inc(p, > se.nr_wakeups_idle); > diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c > index a8f89bc..13f728e 100644 > --- a/kernel/sched_rt.c > +++ b/kernel/sched_rt.c > @@ -1173,13 +1173,6 @@ static int find_lowest_rq(struct task_struct *task) > return -1; /* No targets found */ > > /* > - * Only consider CPUs that are usable for migration. > - * I guess we might want to change cpupri_find() to ignore those > - * in the first place. > - */ > - cpumask_and(lowest_mask, lowest_mask, cpu_active_mask); > - > - /* > * At this point we have built a mask of cpus representing the > * lowest priority tasks in the system. Now we want to elect > * the best one based on our affinity and topology. > > -- > 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/
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