From: Josh Don <joshdon@google.com> To: cruzzhao <cruzzhao@linux.alibaba.com> Cc: Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>, Johannes Weiner <hannes@cmpxchg.org>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Steven Rostedt <rostedt@goodmis.org>, Benjamin Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>, Daniel Bristot de Oliveira <bristot@redhat.com>, cgroups@vger.kernel.org, linux-kernel <linux-kernel@vger.kernel.org> Subject: Re: [PATCH v2 2/3] sched/core: Forced idle accounting per-cpu Date: Fri, 14 Jan 2022 15:40:43 -0800 [thread overview] Message-ID: <CABk29Nu0iCs83VjuipEohL63mdUg_4L-=dKPS0yzE=SfYXtcxw@mail.gmail.com> (raw) In-Reply-To: <86fbc313-e179-0cbd-8f5b-66e7b5964b14@linux.alibaba.com> > > 1) From your v1, I still wasn't quite sure if the per-cpu time was > > useful or not for you versus a single overall sum (ie. I think other > > metrics could be more useful for analyzing steal_cookie if that's what > > you're specifically interested in). Do you definitely want the per-cpu > > totals? > > > IMO, the per-cpu forced idle time can help us get to know whether the > forced idle time is uniform among the core, or among all the cpus. IMO, > it's a kind of balance. Sure, I'm not opposed to it. > > 2) If your cgroup accounting patch is merged, do you still want this > > patch? You can grab the global values from the root cgroup (assuming > > you have cgroups enabled). The only potential gap is if you need > > per-cpu totals, though I'm working to add percpu stats to cgroup-v2: > > https://lkml.kernel.org/r/%3C20220107234138.1765668-1-joshdon@google.com%3E > > If cgroup accounting patch is merged, this patch is still needed. > > Consider the following scenario: > Task p of cgroup A is running on cpu x, and it forces cpu y into idle > for t ns. The forceidle time of cgroup A on cpu x increases t ns, and > the forcedidle time of cpu y increases t ns. > > That is, the force idle time of cgroup is defined as the forced idle > time it caused, and the force idle time of cpu is defined as the time > the cpu is forced into idle, which have different meanings from each other. > > And for SMT > 2, we cannot caculate the forced idle time of cpu x from > the cgroup interface. Ack. Note that the patch I linked above for per-cpu stats for cgroup-v2 has been nack'd, so it is unlikely we'll have kernel exports for cgroup-v2 per-cpu stats (but perhaps some export via BPF). In v2, we could at least export the cgroup sum force idle time in cpu.stat, if you feel it would be useful and want to add the accounting to rstat. If you really just want the per-cpu root stats then I'm fine with skipping cgroup for now.
WARNING: multiple messages have this Message-ID (diff)
From: Josh Don <joshdon-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> To: cruzzhao <cruzzhao-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Zefan Li <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Vincent Guittot <vincent.guittot-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Dietmar Eggemann <dietmar.eggemann-5wv7dgnIgG8@public.gmane.org>, Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Benjamin Segall <bsegall-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>, Daniel Bristot de Oliveira <bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> Subject: Re: [PATCH v2 2/3] sched/core: Forced idle accounting per-cpu Date: Fri, 14 Jan 2022 15:40:43 -0800 [thread overview] Message-ID: <CABk29Nu0iCs83VjuipEohL63mdUg_4L-=dKPS0yzE=SfYXtcxw@mail.gmail.com> (raw) In-Reply-To: <86fbc313-e179-0cbd-8f5b-66e7b5964b14-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> > > 1) From your v1, I still wasn't quite sure if the per-cpu time was > > useful or not for you versus a single overall sum (ie. I think other > > metrics could be more useful for analyzing steal_cookie if that's what > > you're specifically interested in). Do you definitely want the per-cpu > > totals? > > > IMO, the per-cpu forced idle time can help us get to know whether the > forced idle time is uniform among the core, or among all the cpus. IMO, > it's a kind of balance. Sure, I'm not opposed to it. > > 2) If your cgroup accounting patch is merged, do you still want this > > patch? You can grab the global values from the root cgroup (assuming > > you have cgroups enabled). The only potential gap is if you need > > per-cpu totals, though I'm working to add percpu stats to cgroup-v2: > > https://lkml.kernel.org/r/%3C20220107234138.1765668-1-joshdon-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org%3E > > If cgroup accounting patch is merged, this patch is still needed. > > Consider the following scenario: > Task p of cgroup A is running on cpu x, and it forces cpu y into idle > for t ns. The forceidle time of cgroup A on cpu x increases t ns, and > the forcedidle time of cpu y increases t ns. > > That is, the force idle time of cgroup is defined as the forced idle > time it caused, and the force idle time of cpu is defined as the time > the cpu is forced into idle, which have different meanings from each other. > > And for SMT > 2, we cannot caculate the forced idle time of cpu x from > the cgroup interface. Ack. Note that the patch I linked above for per-cpu stats for cgroup-v2 has been nack'd, so it is unlikely we'll have kernel exports for cgroup-v2 per-cpu stats (but perhaps some export via BPF). In v2, we could at least export the cgroup sum force idle time in cpu.stat, if you feel it would be useful and want to add the accounting to rstat. If you really just want the per-cpu root stats then I'm fine with skipping cgroup for now.
next prev parent reply other threads:[~2022-01-14 23:40 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-01-11 9:55 [PATCH v2 0/3] Accounting forced idle time per cpu and per cgroup Cruz Zhao 2022-01-11 9:55 ` Cruz Zhao 2022-01-11 9:55 ` [PATCH v2 1/3] sched/core: Accounting forceidle time for all tasks except idle task Cruz Zhao 2022-01-11 9:55 ` Cruz Zhao 2022-01-11 23:52 ` Josh Don 2022-01-18 11:18 ` [tip: sched/urgent] " tip-bot2 for Cruz Zhao 2022-01-11 9:56 ` [PATCH v2 2/3] sched/core: Forced idle accounting per-cpu Cruz Zhao 2022-01-12 1:59 ` Josh Don 2022-01-12 1:59 ` Josh Don 2022-01-14 15:04 ` cruzzhao 2022-01-14 15:04 ` cruzzhao 2022-01-14 23:40 ` Josh Don [this message] 2022-01-14 23:40 ` Josh Don 2022-01-12 12:27 ` Peter Zijlstra 2022-01-12 12:27 ` Peter Zijlstra 2022-01-14 11:06 ` cruzzhao 2022-01-11 9:56 ` [PATCH v2 3/3] sched/core: Force idle accounting per cgroup Cruz Zhao 2022-01-11 9:56 ` Cruz Zhao 2022-01-12 20:42 ` Tejun Heo 2022-01-12 20:42 ` Tejun Heo 2022-01-14 11:13 ` cruzzhao 2022-01-14 11:13 ` cruzzhao 2022-01-14 16:39 ` Tejun Heo 2022-01-14 16:39 ` Tejun Heo 2022-01-12 21:27 ` kernel test robot
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to='CABk29Nu0iCs83VjuipEohL63mdUg_4L-=dKPS0yzE=SfYXtcxw@mail.gmail.com' \ --to=joshdon@google.com \ --cc=bristot@redhat.com \ --cc=bsegall@google.com \ --cc=cgroups@vger.kernel.org \ --cc=cruzzhao@linux.alibaba.com \ --cc=dietmar.eggemann@arm.com \ --cc=hannes@cmpxchg.org \ --cc=juri.lelli@redhat.com \ --cc=linux-kernel@vger.kernel.org \ --cc=lizefan.x@bytedance.com \ --cc=mgorman@suse.de \ --cc=mingo@redhat.com \ --cc=peterz@infradead.org \ --cc=rostedt@goodmis.org \ --cc=tj@kernel.org \ --cc=vincent.guittot@linaro.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.