From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C54AC433F5 for ; Wed, 10 Nov 2021 09:04:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EDB5B61241 for ; Wed, 10 Nov 2021 09:04:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EDB5B61241 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 875826B006C; Wed, 10 Nov 2021 04:04:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 825E46B0071; Wed, 10 Nov 2021 04:04:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 714386B0072; Wed, 10 Nov 2021 04:04:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id 606026B006C for ; Wed, 10 Nov 2021 04:04:36 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 27F4B800A4 for ; Wed, 10 Nov 2021 09:04:36 +0000 (UTC) X-FDA: 78792434952.20.913A399 Received: from mail-qk1-f170.google.com (mail-qk1-f170.google.com [209.85.222.170]) by imf26.hostedemail.com (Postfix) with ESMTP id 967AA20019C9 for ; Wed, 10 Nov 2021 09:04:36 +0000 (UTC) Received: by mail-qk1-f170.google.com with SMTP id de30so1905825qkb.0 for ; Wed, 10 Nov 2021 01:04:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OfmFNwr+aVtdehKioEcpUngJUmRgTzAF3GcrUhygPBc=; b=lPHB8F/JVchkS0M1d9X4iOqu8LGGmPWqijuWSfWDuJVgfua/d7PF2mB4BU1cswgZh3 VeU17KVNzCHED+9ja+0WGteSoOXimLD2x9u74BoSY4hT6+K1H6vz74u6isrzpObHLiya ljud+uOnmHrtgXTq/ZcCFpOOEENRpr90e3d8aTu7ZgKIUa/JfIvZGXHxXQwBoxqYbJZn AycQ1IWyIP+PADqEOn/bkEumhtca2RRCZwDsB0V8oqfjDC9BjaUBNNzqdOIXMlr9AVnY kgHrm9l4EPXKQkIYoA6vfaW2ljuGcQBCrmaDcyrnMBYopHOsy82TH5DJyCYSfF+NenLL GwEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OfmFNwr+aVtdehKioEcpUngJUmRgTzAF3GcrUhygPBc=; b=tS1tJznOuf/MS6GArps2TKOnoUYiLB9Sf102fUFKSWczfLFhCmcXMh3HAL1hsE7o2y 0UvdmlvypOkYNnoRCagGrEFgfeOEJX3/gx1PMdj3rPRVmtdcaWR0Inp7JVY39WTgXn8c p6I42pshpIFR4DAqQWHSS1Bkl1sorav04kf3qyMOBQWk7rr/eAILSZ0+2ElchZ7ZZk78 sswOdGJHPT3Css9zqklRXFP8mqpp5IiXi+I0CIkjpydLn7Fm7RId1S4vVeKBaEZYspNG 8Wx8Pfq80fcbGxnYsrLflKMhZfVLNxxNNy7ZCNKLIQsoCmgAQxXQOWsvq+jh266qdRyR bvvg== X-Gm-Message-State: AOAM5323exNzlrYbTpZQAqMnMt+R4oJ0ao81Q3NHV4OkMT6x+aVq1zMg RevlgpmU7m5KvTEeOiUb8TjN5kj2Z7JGka6Skyk= X-Google-Smtp-Source: ABdhPJxXZI3RG/ewp+YCny9S+xPFxMW+JahhkmYAalGpHIIOv/XBRAMhua860RZgfTHKB6d6lS5zo0luPqBTLf6YU+U= X-Received: by 2002:a37:4041:: with SMTP id n62mr10973112qka.225.1636535075083; Wed, 10 Nov 2021 01:04:35 -0800 (PST) MIME-Version: 1.0 References: <1634278612-17055-1-git-send-email-huangzhaoyang@gmail.com> In-Reply-To: From: Zhaoyang Huang Date: Wed, 10 Nov 2021 17:04:14 +0800 Message-ID: Subject: Re: [Resend PATCH] psi : calc cfs task memstall time more precisely To: Vincent Guittot Cc: Peter Zijlstra , Johannes Weiner , Andrew Morton , Michal Hocko , Vladimir Davydov , Zhaoyang Huang , "open list:MEMORY MANAGEMENT" , LKML Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="lPHB8F/J"; spf=pass (imf26.hostedemail.com: domain of huangzhaoyang@gmail.com designates 209.85.222.170 as permitted sender) smtp.mailfrom=huangzhaoyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 967AA20019C9 X-Stat-Signature: fry8x4ux6yo3mmia8uafdjg8rxph733q X-HE-Tag: 1636535076-1563 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000076, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 10, 2021 at 4:49 PM Vincent Guittot wrote: > > On Tue, 9 Nov 2021 at 15:56, Peter Zijlstra wrote: > > > > On Tue, Nov 02, 2021 at 03:47:33PM -0400, Johannes Weiner wrote: > > > CC peterz as well for rt and timekeeping magic > > > > > > On Fri, Oct 15, 2021 at 02:16:52PM +0800, Huangzhaoyang wrote: > > > > From: Zhaoyang Huang > > > > > > > > In an EAS enabled system, there are two scenarios discordant to current design, > > > > > > > > 1. workload used to be heavy uneven among cores for sake of scheduler policy. > > > > RT task usually preempts CFS task in little core. > > > > 2. CFS task's memstall time is counted as simple as exit - entry so far, which > > > > ignore the preempted time by RT, DL and Irqs. > > > > It ignores preemption full-stop. I don't see why RT/IRQ should be > > special cased here. > > > > > > With these two constraints, the percpu nonidle time would be mainly consumed by > > > > none CFS tasks and couldn't be averaged. Eliminating them by calc the time growth > > > > via the proportion of cfs_rq's utilization on the whole rq. > > > > > > > > +static unsigned long psi_memtime_fixup(u32 growth) > > > > +{ > > > > + struct rq *rq = task_rq(current); > > > > + unsigned long growth_fixed = (unsigned long)growth; > > > > + > > > > + if (!(current->policy == SCHED_NORMAL || current->policy == SCHED_BATCH)) > > > > + return growth_fixed; > > > > + > > > > + if (current->in_memstall) > > > > + growth_fixed = div64_ul((1024 - rq->avg_rt.util_avg - rq->avg_dl.util_avg > > > > + - rq->avg_irq.util_avg + 1) * growth, 1024); > > > > + > > > > + return growth_fixed; > > > > +} > > > > + > > > > static void init_triggers(struct psi_group *group, u64 now) > > > > { > > > > struct psi_trigger *t; > > > > @@ -658,6 +675,7 @@ static void record_times(struct psi_group_cpu *groupc, u64 now) > > > > } > > > > > > > > if (groupc->state_mask & (1 << PSI_MEM_SOME)) { > > > > + delta = psi_memtime_fixup(delta); > > > > > > Ok, so we want to deduct IRQ and RT preemption time from the memstall > > > period of an active reclaimer, since it's technically not stalled on > > > memory during this time but on CPU. > > > > > > However, we do NOT want to deduct IRQ and RT time from memstalls that > > > are sleeping on refaults swapins, since they are not affected by what > > > is going on on the CPU. > > > > I think that focus on RT/IRQ is mis-guided here, and the implementation > > is horrendous. > > > > So the fundamental question seems to be; and I think Johannes is the one > > to answer that: What time-base do these metrics want to use? > > > > Do some of these states want to account in task-time instead of > > wall-time perhaps? I can't quite remember, but vague memories are > > telling me most of the PSI accounting was about blocked tasks, not > > running tasks, which makes all this rather more complicated. > > I tend to agree with this. > Using rq_clock_task(rq) instead of cpu_clock(cpu) will remove the time > spent under interrupt as an example > and AFAICT, rq->clock_task is updated before calling psi function thanks vincent. Could rq_clock_task help on removing the preempted time of CFS task by RT/DL, which is the mainly part we want to solve on memstall time. > > > > > Randomly scaling time as proposed seems almost certainly wrong. What > > would that make the stats mean?