Messages in this thread | | | Date | Thu, 30 Jul 2009 11:10:50 -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: > 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)... > }
NM. My first instinct was correct.
We need the result of sd->span, cpus_allowed, and active_map. The submitted logic (or the original) is correct, and my comment above is wrong.
Sorry for the noise, -Greg
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