Messages in this thread Patch in this message | | | Subject | Re: [LKP] Re: [sched/hotplug] 2558aacff8: will-it-scale.per_thread_ops -1.6% regression | From | Xing Zhengjun <> | Date | Tue, 15 Dec 2020 13:35:46 +0800 |
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On 12/11/2020 12:14 AM, Peter Zijlstra wrote: > On Thu, Dec 10, 2020 at 04:18:59PM +0800, kernel test robot wrote: >> FYI, we noticed a -1.6% regression of will-it-scale.per_thread_ops due to commit: >> commit: 2558aacff8586699bcd248b406febb28b0a25de2 ("sched/hotplug: Ensure only per-cpu kthreads run during hotplug") > > Mooo, weird but whatever. Does the below help at all?
I test the patch, the regression reduced to -0.6%.
========================================================================================= tbox_group/testcase/rootfs/kconfig/compiler/nr_task/mode/test/cpufreq_governor/ucode: lkp-cpl-4sp1/will-it-scale/debian-10.4-x86_64-20200603.cgz/x86_64-rhel-8.3/gcc-9/100%/thread/sched_yield/performance/0x700001e
commit: 565790d28b1e33ee2f77bad5348b99f6dfc366fd 2558aacff8586699bcd248b406febb28b0a25de2 4b26139b8db627a55043183614a32b0aba799d27 (this test patch)
565790d28b1e33ee 2558aacff8586699bcd248b406f 4b26139b8db627a55043183614a ---------------- --------------------------- --------------------------- %stddev %change %stddev %change %stddev \ | \ | \ 4.011e+08 -1.6% 3.945e+08 -0.6% 3.989e+08 will-it-scale.144.threads 2785455 -1.6% 2739520 -0.6% 2769967 will-it-scale.per_thread_ops 4.011e+08 -1.6% 3.945e+08 -0.6% 3.989e+08 will-it-scale.workload
> > --- > kernel/sched/core.c | 40 +++++++++++++++------------------------- > kernel/sched/sched.h | 13 +++++-------- > 2 files changed, 20 insertions(+), 33 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 7af80c3fce12..f80245c7f903 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3985,15 +3985,20 @@ static void do_balance_callbacks(struct rq *rq, struct callback_head *head) > } > } > > +static void balance_push(struct rq *rq); > + > +struct callback_head balance_push_callback = { > + .next = NULL, > + .func = (void (*)(struct callback_head *))balance_push, > +}; > + > static inline struct callback_head *splice_balance_callbacks(struct rq *rq) > { > struct callback_head *head = rq->balance_callback; > > lockdep_assert_held(&rq->lock); > - if (head) { > + if (head) > rq->balance_callback = NULL; > - rq->balance_flags &= ~BALANCE_WORK; > - } > > return head; > } > @@ -4014,21 +4019,6 @@ static inline void balance_callbacks(struct rq *rq, struct callback_head *head) > } > } > > -static void balance_push(struct rq *rq); > - > -static inline void balance_switch(struct rq *rq) > -{ > - if (likely(!rq->balance_flags)) > - return; > - > - if (rq->balance_flags & BALANCE_PUSH) { > - balance_push(rq); > - return; > - } > - > - __balance_callbacks(rq); > -} > - > #else > > static inline void __balance_callbacks(struct rq *rq) > @@ -4044,10 +4034,6 @@ static inline void balance_callbacks(struct rq *rq, struct callback_head *head) > { > } > > -static inline void balance_switch(struct rq *rq) > -{ > -} > - > #endif > > static inline void > @@ -4075,7 +4061,7 @@ static inline void finish_lock_switch(struct rq *rq) > * prev into current: > */ > spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_); > - balance_switch(rq); > + __balance_callbacks(rq); > raw_spin_unlock_irq(&rq->lock); > } > > @@ -7256,6 +7242,10 @@ static void balance_push(struct rq *rq) > > lockdep_assert_held(&rq->lock); > SCHED_WARN_ON(rq->cpu != smp_processor_id()); > + /* > + * Ensure the thing is persistent until balance_push_set(, on = false); > + */ > + rq->balance_callback = &balance_push_callback; > > /* > * Both the cpu-hotplug and stop task are in this case and are > @@ -7305,9 +7295,9 @@ static void balance_push_set(int cpu, bool on) > > rq_lock_irqsave(rq, &rf); > if (on) > - rq->balance_flags |= BALANCE_PUSH; > + rq->balance_callback = &balance_push_callback; > else > - rq->balance_flags &= ~BALANCE_PUSH; > + rq->balance_callback = NULL; > rq_unlock_irqrestore(rq, &rf); > } > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index f5acb6c5ce49..12ada79d40f3 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -975,7 +975,6 @@ struct rq { > unsigned long cpu_capacity_orig; > > struct callback_head *balance_callback; > - unsigned char balance_flags; > > unsigned char nohz_idle_balance; > unsigned char idle_balance; > @@ -1226,6 +1225,8 @@ struct rq_flags { > #endif > }; > > +extern struct callback_head balance_push_callback; > + > /* > * Lockdep annotation that avoids accidental unlocks; it's like a > * sticky/continuous lockdep_assert_held(). > @@ -1243,9 +1244,9 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf) > #ifdef CONFIG_SCHED_DEBUG > rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); > rf->clock_update_flags = 0; > -#endif > #ifdef CONFIG_SMP > - SCHED_WARN_ON(rq->balance_callback); > + SCHED_WARN_ON(rq->balance_callback && rq->balance_callback != &balance_push_callback); > +#endif > #endif > } > > @@ -1408,9 +1409,6 @@ init_numa_balancing(unsigned long clone_flags, struct task_struct *p) > > #ifdef CONFIG_SMP > > -#define BALANCE_WORK 0x01 > -#define BALANCE_PUSH 0x02 > - > static inline void > queue_balance_callback(struct rq *rq, > struct callback_head *head, > @@ -1418,13 +1416,12 @@ queue_balance_callback(struct rq *rq, > { > lockdep_assert_held(&rq->lock); > > - if (unlikely(head->next || (rq->balance_flags & BALANCE_PUSH))) > + if (unlikely(head->next || rq->balance_callback == &balance_push_callback)) > return; > > head->func = (void (*)(struct callback_head *))func; > head->next = rq->balance_callback; > rq->balance_callback = head; > - rq->balance_flags |= BALANCE_WORK; > } > > #define rcu_dereference_check_sched_domain(p) \ > _______________________________________________ > LKP mailing list -- lkp@lists.01.org > To unsubscribe send an email to lkp-leave@lists.01.org >
-- Zhengjun Xing
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