From: Mel Gorman <email@example.com> To: Aubrey Li <firstname.lastname@example.org> Cc: Barry Song <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [PATCH 8/9] sched/fair: select idle cpu from idle cpumask for task wakeup Date: Fri, 17 Sep 2021 14:35:12 +0100 [thread overview] Message-ID: <20210917133512.GH3959@techsingularity.net> (raw) In-Reply-To: <email@example.com> On Fri, Sep 17, 2021 at 05:11:11PM +0800, Aubrey Li wrote: > On 9/17/21 12:15 PM, Barry Song wrote: > >> @@ -4965,6 +4965,7 @@ void scheduler_tick(void) > >> > >> #ifdef CONFIG_SMP > >> rq->idle_balance = idle_cpu(cpu); > >> + update_idle_cpumask(cpu, rq->idle_balance); > >> trigger_load_balance(rq); > >> #endif > >> } > > > > might be stupid, a question bothering yicong and me is that why don't we > > choose to update_idle_cpumask() while idle task exits and switches to a > > normal task? > > I implemented that way and we discussed before(RFC v1 ?), updating a cpumask > at every enter/exit idle is more expensive than we expected, though it's > per LLC domain, Vincent saw a significant regression IIRC. You can also > take a look at nohz.idle_cpus_mask as a reference. > It's possible to track it differently and I prototyped it some time back. The results were mixed at the time. It helped some workloads and was marginal on others. It appeared to help hackbench but I found that hackbench is much more vulnerable to the wakeup_granularity and overscheduling. For hackbench, it makes more sense to target that directly before revisiting the alt-idlecore to see what it really helps. I'm waiting on test results on various ways wakeup_gran can be scaled depending on rq activity. For alternative idle core tracking, the current 5.15-rc1 rebase prototype looks like this https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/commit/?h=sched-altidlecore-v2r8&id=b2af1a88245f6cbeb28343e89f3183a77b29d52d Test results still pending and as usual the queue is busy. I swear, my primary bottleneck for doing anything is benchmark and validation :( -- Mel Gorman SUSE Labs
next prev parent reply other threads:[~2021-09-17 13:36 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-26 10:22 [RFC PATCH 0/9] Modify and/or delete SIS_PROP Mel Gorman 2021-07-26 10:22 ` [PATCH 1/9] sched/fair: Track efficiency of select_idle_sibling Mel Gorman 2021-07-26 10:22 ` [PATCH 2/9] sched/fair: Track efficiency of task recent_used_cpu Mel Gorman 2021-07-26 10:22 ` [PATCH 3/9] sched/fair: Track efficiency of select_idle_core Mel Gorman 2021-07-26 10:22 ` [PATCH 4/9] sched/fair: Use prev instead of new target as recent_used_cpu Mel Gorman 2021-07-26 10:22 ` [PATCH 5/9] sched/fair: Avoid a second scan of target in select_idle_cpu Mel Gorman 2021-07-26 10:22 ` [PATCH 6/9] sched/fair: Make select_idle_cpu() proportional to cores Mel Gorman 2021-07-26 10:22 ` [PATCH 7/9] sched/fair: Enforce proportional scan limits when scanning for an idle core Mel Gorman 2021-08-02 10:52 ` Song Bao Hua (Barry Song) 2021-08-04 10:22 ` Mel Gorman 2021-07-26 10:22 ` [PATCH 8/9] sched/fair: select idle cpu from idle cpumask for task wakeup Mel Gorman 2021-08-02 10:41 ` Song Bao Hua (Barry Song) 2021-08-04 10:26 ` Mel Gorman 2021-08-05 0:23 ` Aubrey Li 2021-09-17 3:44 ` Barry Song 2021-09-17 4:15 ` Barry Song 2021-09-17 9:11 ` Aubrey Li 2021-09-17 13:35 ` Mel Gorman [this message] 2021-07-26 10:22 ` [PATCH 9/9] sched/core: Delete SIS_PROP and rely on the idle cpu mask Mel Gorman
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