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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46FE4C10F13 for ; Tue, 19 Jan 2021 18:28:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A54020706 for ; Tue, 19 Jan 2021 18:28:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390471AbhASRAY (ORCPT ); Tue, 19 Jan 2021 12:00:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389193AbhASQ7Y (ORCPT ); Tue, 19 Jan 2021 11:59:24 -0500 Received: from mail-qt1-x82e.google.com (mail-qt1-x82e.google.com [IPv6:2607:f8b0:4864:20::82e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BE31C061574 for ; Tue, 19 Jan 2021 08:58:44 -0800 (PST) Received: by mail-qt1-x82e.google.com with SMTP id z6so7117019qtn.0 for ; Tue, 19 Jan 2021 08:58:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ZrHO+yIyrdnmaVFMwMvHwDYxfdcxIe8NtcCENOohqSk=; b=IjO3yV9X3nKmpNx8G+WcMwGh4WEgM94OpZUe3C4BCxS9AKRrGEhbWZO7OTjbH7Ne3x hBn/tqmq9p/SRMGTavW8121ebd0zIeiAp/LuvwT6FMfCYkBE04QBVr87DOd2YF1dJ5XU VGAQcehIYy7JkkebnKqVX9kRX0Qn0F76T8Y/cDI+QGt0gljuxp0EF85EX96ntV+03wOk 7KbKWoG2E/FhQykR4/gb9nAj7FAsU+Ia39sjuA/EFf/99riTedyctkT0L4TZQXUZwWmk JAQBPrNevBWhtXC2xw3srAkrdbawiF+K0gCtNuEOPdxq0l1YTimU5KpCR879RCLBNVad 7RkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ZrHO+yIyrdnmaVFMwMvHwDYxfdcxIe8NtcCENOohqSk=; b=R3aIcraTWiu3Vbbq7Z6h+cMYTd59BElKg1RQ3pSp9JHMeHwFxWChHm7C6LnJw+OA+X 9tMw0zEg/hSKTg3o9cRmp79FcQszRyjABCXd7V4MBM2NJet+FBDNWf6JGKT2j/ALFK8N ml1xKjjhmOZWTj39jSPh8w2o5BE9rN9w/yqno4Yrh9wit9U3l3y63npEX7eYs+sxeYSW KTkgbd/5ma87HPkGSNSbdWvy4XUHxbDUpouBmRSf4gWOrHviy95/DU6GfQyGOOop3rZq vJKm1m852en4nmF/yxIR/Eb/co+05/g4sydPNjRZ3TDP/z2yiwkLxSHWMlYFUSlu0zSQ ADOw== X-Gm-Message-State: AOAM531h5FowCPMd7VVf0hepJd3utnE0ZLd3MimAUmApH00Ek+nMa2qh 7+U9ml+fUwqRkubNSGyeSc7GNQ== X-Google-Smtp-Source: ABdhPJzsyWLPgohCl7XB5LwIp8dV/Pk3lXKhNGMeii0fsyJDhxQqGVWDod3V+nlOOW8bx/cWiERhNg== X-Received: by 2002:a05:622a:28d:: with SMTP id z13mr5136519qtw.87.1611075523954; Tue, 19 Jan 2021 08:58:43 -0800 (PST) Received: from localhost (70.44.39.90.res-cmts.bus.ptd.net. [70.44.39.90]) by smtp.gmail.com with ESMTPSA id m21sm8279408qtq.52.2021.01.19.08.58.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 08:58:43 -0800 (PST) Date: Tue, 19 Jan 2021 11:58:42 -0500 From: Johannes Weiner To: Muchun Song Cc: mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memcontrol: skip propagate percpu vmstat values to current memcg Message-ID: References: <20210119052744.96765-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210119052744.96765-1-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 19, 2021 at 01:27:44PM +0800, Muchun Song wrote: > The current memcg will be freed soon, so updating it's vmstat and > vmevent values is pointless. Just skip updating it. > > Signed-off-by: Muchun Song Oof, that's pretty subtle! Somebody trying to refactor that code for other purposes may not immediately notice that optimization and add potentially tedious bugs. How much does this save? Cgroup creation and deletion isn't really considered a hot path. It takes global locks and such...