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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1E92C433EF for ; Tue, 8 Feb 2022 17:58:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E72456B0071; Tue, 8 Feb 2022 12:58:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E1F976B0075; Tue, 8 Feb 2022 12:58:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CE76D6B0078; Tue, 8 Feb 2022 12:58:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0054.hostedemail.com [216.40.44.54]) by kanga.kvack.org (Postfix) with ESMTP id C04BF6B0071 for ; Tue, 8 Feb 2022 12:58:41 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7DD8596F1B for ; Tue, 8 Feb 2022 17:58:41 +0000 (UTC) X-FDA: 79120372842.27.C9BFFA3 Received: from mail-lf1-f48.google.com (mail-lf1-f48.google.com [209.85.167.48]) by imf01.hostedemail.com (Postfix) with ESMTP id BECEB40002 for ; Tue, 8 Feb 2022 17:58:40 +0000 (UTC) Received: by mail-lf1-f48.google.com with SMTP id f10so34769053lfu.8 for ; Tue, 08 Feb 2022 09:58:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+CQgr5ve9zRzrNvBukJhKnL+pLaCQfJXdaqimLxBtNw=; b=E2UoFvQVzm+7bHzoMVzVa5ubhrCgFht99UH8rY/REMe83oGfWQbtPaijzy5V1htQAM BkkNX7I3Loju1qPFQ5SKiuN5gRGm//MXKuPFU/+lAiqJjC612uxlmflrzBxtp0cWwYp0 0Kn0O12jqVtQTdqiqNJsAs/kerC4f1FDmDdBVHLKxxjOtW327uXZ7o+HvwuC70xxjlJl gSSvHFw3+VHuGjkG/d+Df6+eQ0ecY2ISbQ4wyFZX0Fpw5/u3TLH17KBnUcAF9XaLd/bl if5ThueUvsEl4EwY0MmqrEAzcqWRBNvYY6S6rsWOgW3CuGWUHJPk569Mef72P68WBent D8HA== 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=+CQgr5ve9zRzrNvBukJhKnL+pLaCQfJXdaqimLxBtNw=; b=N0qBAR9JWYPlIUJ8yfsFtebGzV0FUehUx/9ZxZadcFbIqD5rBmkxRbgWrBkspHiwAd m4RglHWMh5dRwEEqNWOxAGm8TStKOCTIrtSMCHdtbQePxalra4CxZ5I0DwkluP5joaGu fs9B895lyjj9g5JSaSB1ncLF4VX5zMOCcxg3dTf5gSG6YKS5KFdWnjMuBRO6h11gyUrJ 8l4WQ4c7ceayoDeJmH/8q7KBdTAMW2j+MwXhPjQT0atatL2UtLqRwfCvI9EwTdaAnmzc 1v+EJEl9aI4ENmSJg9tQfy5aIYCIKR7kd429JKBQ37C1KXGzYOfUBTlAuJ+Jr6VpcvZy draw== X-Gm-Message-State: AOAM533eFGUcFkpewsZ0TB15SwE2kEQm4kLPTZ/MBiPdyfSF++Tqrp0e 6MI/Ai1PHGlvAlmzUr0Xg8kZOkBmyLCLrjQdgNu96Q== X-Google-Smtp-Source: ABdhPJzAJtv7/46SwEDqx+yw/l/cxQ/RFIcqnChaJ8qRLteh+2fRg1hhY9W/DgaPCSXAVJRA9+8dkpNfdfi5A44xCvg= X-Received: by 2002:ac2:43ad:: with SMTP id t13mr3734442lfl.8.1644343119017; Tue, 08 Feb 2022 09:58:39 -0800 (PST) MIME-Version: 1.0 References: <20220125164337.2071854-1-bigeasy@linutronix.de> <20220125164337.2071854-4-bigeasy@linutronix.de> In-Reply-To: From: Shakeel Butt Date: Tue, 8 Feb 2022 09:58:27 -0800 Message-ID: Subject: Re: [PATCH 3/4] mm/memcg: Add a local_lock_t for IRQ and TASK object. To: Michal Hocko Cc: Waiman Long , Sebastian Andrzej Siewior , Cgroups , Linux MM , Andrew Morton , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Peter Zijlstra , Thomas Gleixner , Vladimir Davydov Content-Type: text/plain; charset="UTF-8" X-Rspam-User: Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=E2UoFvQV; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf01.hostedemail.com: domain of shakeelb@google.com designates 209.85.167.48 as permitted sender) smtp.mailfrom=shakeelb@google.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: BECEB40002 X-Stat-Signature: b3atgatase157sw7fn78xt4j73133qi4 X-HE-Tag: 1644343120-968077 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 3, 2022 at 2:10 AM Michal Hocko wrote: > > On Thu 03-02-22 10:54:07, Sebastian Andrzej Siewior wrote: > > On 2022-02-01 16:29:35 [+0100], Michal Hocko wrote: > > > > > Sorry, I know that this all is not really related to your work but if > > > > > the original optimization is solely based on artificial benchmarks then > > > > > I would rather drop it and also make your RT patchset easier. > > > > > > > > Do you have any real-world benchmark in mind? Like something that is > > > > already used for testing/ benchmarking and would fit here? > > > > > > Anything that even remotely resembles a real allocation heavy workload. > > > > So I figured out that build the kernel as user triggers the allocation > > path in_task() and in_interrupt(). I booted a PREEMPT_NONE kernel and > > run "perf stat -r 5 b.sh" where b.sh unpacks a kernel and runs a > > allmodconfig build on /dev/shm. The slow disk should not be a problem. > > > > With the optimisation: > > | Performance counter stats for './b.sh' (5 runs): > > | > > | 43.367.405,59 msec task-clock # 30,901 CPUs utilized ( +- 0,01% ) > > | 7.393.238 context-switches # 170,499 /sec ( +- 0,13% ) > > | 832.364 cpu-migrations # 19,196 /sec ( +- 0,15% ) > > | 625.235.644 page-faults # 14,419 K/sec ( +- 0,00% ) > > | 103.822.081.026.160 cycles # 2,394 GHz ( +- 0,01% ) > > | 75.392.684.840.822 stalled-cycles-frontend # 72,63% frontend cycles idle ( +- 0,02% ) > > | 54.971.177.787.990 stalled-cycles-backend # 52,95% backend cycles idle ( +- 0,02% ) > > | 69.543.893.308.966 instructions # 0,67 insn per cycle > > | # 1,08 stalled cycles per insn ( +- 0,00% ) > > | 14.585.269.354.314 branches # 336,357 M/sec ( +- 0,00% ) > > | 558.029.270.966 branch-misses # 3,83% of all branches ( +- 0,01% ) > > | > > | 1403,441 +- 0,466 seconds time elapsed ( +- 0,03% ) > > > > > > With the optimisation disabled: > > | Performance counter stats for './b.sh' (5 runs): > > | > > | 43.354.742,31 msec task-clock # 30,869 CPUs utilized ( +- 0,01% ) > > | 7.394.210 context-switches # 170,601 /sec ( +- 0,06% ) > > | 842.835 cpu-migrations # 19,446 /sec ( +- 0,63% ) > > | 625.242.341 page-faults # 14,426 K/sec ( +- 0,00% ) > > | 103.791.714.272.978 cycles # 2,395 GHz ( +- 0,01% ) > > | 75.369.652.256.425 stalled-cycles-frontend # 72,64% frontend cycles idle ( +- 0,01% ) > > | 54.947.610.706.450 stalled-cycles-backend # 52,96% backend cycles idle ( +- 0,01% ) > > | 69.529.388.440.691 instructions # 0,67 insn per cycle > > | # 1,08 stalled cycles per insn ( +- 0,01% ) > > | 14.584.515.016.870 branches # 336,497 M/sec ( +- 0,00% ) > > | 557.716.885.609 branch-misses # 3,82% of all branches ( +- 0,02% ) > > | > > | 1404,47 +- 1,05 seconds time elapsed ( +- 0,08% ) > > > > I'm still open to a more specific test ;) > > Thanks for this test. I do assume that both have been run inside a > non-root memcg. > > Weiman, what was the original motivation for 559271146efc0? Because as > this RT patch shows it makes future changes much more complex and I > would prefer a simpler and easier to maintain code than some micro > optimizations that do not have any visible effect on real workloads. commit 559271146efc0 is a part of patch series "mm/memcg: Reduce kmemcache memory accounting overhead". For perf numbers you can see the cover letter in the commit fdbcb2a6d677 ("mm/memcg: move mod_objcg_state() to memcontrol.c"). BTW I am onboard with preferring simpler code over complicated optimized code.