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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 B56F8C433DB for ; Fri, 5 Feb 2021 15:31:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1DAF7650ED for ; Fri, 5 Feb 2021 15:31:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DAF7650ED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8FE8D6B006C; Fri, 5 Feb 2021 10:31:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8B01E6B0071; Fri, 5 Feb 2021 10:31:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C69F6B007B; Fri, 5 Feb 2021 10:31:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 66F386B006C for ; Fri, 5 Feb 2021 10:31:17 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 282B92481 for ; Fri, 5 Feb 2021 15:31:17 +0000 (UTC) X-FDA: 77784602994.03.blood96_3b06845275e5 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 9BDCF28A26A for ; Fri, 5 Feb 2021 15:31:14 +0000 (UTC) X-HE-Tag: blood96_3b06845275e5 X-Filterd-Recvd-Size: 6790 Received: from mail-pg1-f177.google.com (mail-pg1-f177.google.com [209.85.215.177]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Fri, 5 Feb 2021 15:31:13 +0000 (UTC) Received: by mail-pg1-f177.google.com with SMTP id o7so4800978pgl.1 for ; Fri, 05 Feb 2021 07:31:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=k4OJLV6TXS1KdESPsSN5ElFkZKiwedSKAnd29KVc8KM=; b=1aw6G8+TFmecyaEdtijZI3sTpYEbc4iqst6CcMnq1bl2fPTIIjZ71I95liyMaaTEdM njh8wvV/aPJZI3cAQlg8pI9VCAHNZHuKLMhrGZmIjboD1TagcPOdprngYyDCsor7ncGs 09+hFnX+T6ilxBP80u7+mkj2cilveG/6G+QwnlTtFDjDdpovBSaSLZ5qNqIrefNiphby VSTGt1n3cYWec6DxUohkn8BjxwrXVLyOVle+kB8wOWx2v7YAVSkSqbzliKdWClAuWPGV kqYy8HcxH7eYR3EvDfoIV5Amdw10sOwcttGJzzYnP2+3KWpVN8cAZGNfh6fikwGVHRSY VcsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=k4OJLV6TXS1KdESPsSN5ElFkZKiwedSKAnd29KVc8KM=; b=f83olfe/d/mA4xuECpqu2ir4HMxdT/gP9Rf4EbwshmtoJLNMAOJwzuVIW3sz2mfJTp gAuwWJKfUEXwoR20ZjoDbRPsRvih/1OXNsAR+D9oXubCq0P+w9eaUIsPh4EXaKrek7OL UlAUKDpgR7R7CwVp9rufnFA+LFbggNBcXyiya1YHPni9Soh+bUxF09VIB9vmMhxFwT/Q 5mIfzrahEXfkhIYFQN6CrmoVS+IvKhBvtVCN0q2Ho/PyH9EW0O4eD5Vc17BkisjJ+tS4 DOvVIYWeUNZ+bpsJSmTT+hCGq/h/6jJdBnc0Rjk6FeaEXQ09ewMeOQB+OJ6qZRQbX/Yf qHpQ== X-Gm-Message-State: AOAM530dwsNt3UL9ZufJKyehAxKOr0UPOUAzFwPy7XIhcz7qAloVoxkL mQU7bP4A/1qlwUoqyotjD8loWDEA+hVQ58PUCNabfQ== X-Google-Smtp-Source: ABdhPJwhULqIS5l4qL1BjXkv2y/zKC3UJe21U6D62vItTdYaESCfEqvoP5XrUuqj+ZBAH5RcV/hzjTced12oZpPUHhQ= X-Received: by 2002:a63:de0e:: with SMTP id f14mr4752501pgg.273.1612539072639; Fri, 05 Feb 2021 07:31:12 -0800 (PST) MIME-Version: 1.0 References: <20210205062310.74268-1-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Fri, 5 Feb 2021 23:30:36 +0800 Message-ID: Subject: Re: [External] Re: [PATCH] mm: memcontrol: fix missing wakeup oom task To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Cgroups , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" 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 Fri, Feb 5, 2021 at 8:20 PM Michal Hocko wrote: > > On Fri 05-02-21 19:04:19, Muchun Song wrote: > > On Fri, Feb 5, 2021 at 6:21 PM Michal Hocko wrote: > > > > > > On Fri 05-02-21 17:55:10, Muchun Song wrote: > > > > On Fri, Feb 5, 2021 at 4:24 PM Michal Hocko wrote: > > > > > > > > > > On Fri 05-02-21 14:23:10, Muchun Song wrote: > > > > > > We call memcg_oom_recover() in the uncharge_batch() to wakeup OOM task > > > > > > when page uncharged, but for the slab pages, we do not do this when page > > > > > > uncharged. > > > > > > > > > > How does the patch deal with this? > > > > > > > > When we uncharge a slab page via __memcg_kmem_uncharge, > > > > actually, this path forgets to do this for us compared to > > > > uncharge_batch(). Right? > > > > > > Yes this was more more or less clear (still would have been nicer to be > > > explicit). But you still haven't replied to my question I believe. I > > > assume you rely on refill_stock doing draining but how does this address > > > the problem? Is it sufficient to do wakeups in the batched way? > > > > Sorry, the subject title may not be suitable. IIUC, memcg_oom_recover > > aims to wake up the OOM task when we uncharge the page. > > Yes, your understanding is correct. This is a way to pro-actively wake > up oom victims when the memcg oom handling is outsourced to the > userspace. Please note that I haven't objected to the problem statement. > > I was questioning the fix for the problem. > > > I see uncharge_batch always do this. I am confused why > > __memcg_kmem_uncharge does not. > > Very likely an omission. I haven't checked closely but I suspect this > has been introduced by the recent kmem accounting changes. > > Why didn't you simply do the same thing and call memcg_oom_recover > unconditionally and instead depend on the draining? I suspect this was > because you wanted to recover also when draining which is not necessary > as pointed out in other email. Thanks for your explanations. You are right. It is my fault to depend on the draining. I should call memcg_oom_recover directly in the __memcg_kmem_uncharge. Right? > > [...] > > > > > Does this lead to any code generation improvements? I would expect > > > > > compiler to be clever enough to inline static functions if that pays > > > > > off. If yes make this a patch on its own. > > > > > > > > I have disassembled the code, I see memcg_oom_recover is not > > > > inline. Maybe because memcg_oom_recover has a lot of callers. > > > > Just guess. > > > > > > > > (gdb) disassemble uncharge_batch > > > > [...] > > > > 0xffffffff81341c73 <+227>: callq 0xffffffff8133c420 > > > > 0xffffffff81341c78 <+232>: jmpq 0xffffffff81341bc0 > > > > 0xffffffff81341c7d <+237>: callq 0xffffffff8133e2c0 > > > > > > So does it really help to do the inlining? > > > > I just think memcg_oom_recover is very small, inline maybe > > a good choice. Maybe I am wrong. > > In general I am not overly keen on changes without a proper > justification. In this particular case I would understand that a > function call that will almost never do anything but the test (because > oom_disabled is a rarely used) is just waste of cycles in some hot > paths (e.g. kmem uncharge). Maybe this even has some visible performance > benefit. If this is really the case then would it make sense to guard > this test by the existing cgroup_subsys_on_dfl(memory_cgrp_subsys)? Agree. I think it can improve performance when this function is inline. Guarding the test should be also an improvement on cgroup v2. > -- > Michal Hocko > SUSE Labs