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 9CAC8C64EC4 for ; Thu, 9 Mar 2023 02:33:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DD5FF6B0075; Wed, 8 Mar 2023 21:33:09 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D866E280001; Wed, 8 Mar 2023 21:33:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C4E1B6B007B; Wed, 8 Mar 2023 21:33:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id B5EE06B0075 for ; Wed, 8 Mar 2023 21:33:09 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 6CA65A139E for ; Thu, 9 Mar 2023 02:33:09 +0000 (UTC) X-FDA: 80547787698.19.41D6C63 Received: from mail-pf1-f177.google.com (mail-pf1-f177.google.com [209.85.210.177]) by imf27.hostedemail.com (Postfix) with ESMTP id 74E0D40004 for ; Thu, 9 Mar 2023 02:33:07 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=shopee.com header.s=shopee.com header.b=TndqUjuz; spf=pass (imf27.hostedemail.com: domain of haifeng.xu@shopee.com designates 209.85.210.177 as permitted sender) smtp.mailfrom=haifeng.xu@shopee.com; dmarc=pass (policy=reject) header.from=shopee.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678329187; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=eWBrUih/RRXh6LptA2jqLQdR79LGfEQflDsOHRkNIYE=; b=FuEPxvI2bWrLjaDkH5Xa91XcXZgEwu4QN453HGLF2uyBNkBGl8Xo6iuhC1Th+21LNGUCJn KuYqgURspUzatzc3lqgveJSqawmDkTAjQfeHeJmy1sDm0VhQsWeMXrKIjKlveb1o+qmZHs Ey6m1L8WH6Uj0D+bZTuEhI6L72FdcRs= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=shopee.com header.s=shopee.com header.b=TndqUjuz; spf=pass (imf27.hostedemail.com: domain of haifeng.xu@shopee.com designates 209.85.210.177 as permitted sender) smtp.mailfrom=haifeng.xu@shopee.com; dmarc=pass (policy=reject) header.from=shopee.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678329187; a=rsa-sha256; cv=none; b=zVdNEB8OoTj/rcZfvHbvAfp7Njikhz86JHWE4VRsuPk6Tf7UOxMopkU+mUDRsmSwRVOzNF 93nt4M01e50l0u4TA605cAXaL80wYIeiRkuLiZcQoK6OhP+DZ+tylBYI9hO3CySYNH3e9u DFbrwawVaTIIz4qmp6EUvSq23VP9RbI= Received: by mail-pf1-f177.google.com with SMTP id ay18so631534pfb.2 for ; Wed, 08 Mar 2023 18:33:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shopee.com; s=shopee.com; t=1678329186; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=eWBrUih/RRXh6LptA2jqLQdR79LGfEQflDsOHRkNIYE=; b=TndqUjuz2mhJFsHfOlTwlNVgmSD8i0JOsy5RdKaE+OooTm/W5IcvtRod7Jj015SPmK 3jTaQOKL39NKi7wJcXvgYamueR8FWE91YVcQC7WL0odLoO+33gplRO1qY+KI+kqN/1hf REe3qIWTvHS69jUUmmIuBXVUzYL+bIaKsi/z98XYGKVBalJUpYdyuSBP0/PpdTE7RCer 61+NSoLRWLxr13xZGDBDh+MBp1Z0wlBjPrHZUK4injVDofq9LtLkt2v54/0T3n7dO1Vd aOq101hb8lm0LSjt3NgoN3NMpy4rIq0F9pLuZMnHMd0esDZvO5UE6LcqqVk6refFWpKb tsWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678329186; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=eWBrUih/RRXh6LptA2jqLQdR79LGfEQflDsOHRkNIYE=; b=qMBR82QTsJY8/F9vb8/LqCEvmkr5IwSfyveDNHBqEh/9+Lm4MzZ0KtGPuu5pvQdWtG SOoWl8vdP0JMQfxkuLsszjS0dEERXjcbY1OHWVa+4I/FzxBCGNu8IS7roMbzLRc+jtUA CGPG5yiSp7ZYZiJJaLUXOxJg4U5twyfYRsAvWkFk1UvnNUDgDqepq6Wsy5Z8MdozpFA2 v3VQoWJEukAX7z3Ac1IK9hvukKOiWVTFOWeHmBxcy2dJHVp+5hMrv4kquN4rIWfTgzjS tA+PcFYg2azzjnMdfRHFZV492le03CkkdmY6FPv4n4LKLIjkwVVCTA2Hmi4d9Wdn7BFY 92iw== X-Gm-Message-State: AO0yUKVgzYp3SH4+KgUbTXTgPZw6OwqeKvu2Pw20xWXoso/x3FQJwUjq ubmvaGuCcW1W42nDkL60MXkePA== X-Google-Smtp-Source: AK7set+aAhmSeEQpM5/fO0SMwY482EMidsA9DAGvcoxnyQXhsAvVF4n/vUkj32hjwPt95szWOR1DGQ== X-Received: by 2002:aa7:9418:0:b0:5cd:d766:8a26 with SMTP id x24-20020aa79418000000b005cdd7668a26mr17477255pfo.8.1678329186221; Wed, 08 Mar 2023 18:33:06 -0800 (PST) Received: from [10.54.24.141] ([143.92.118.3]) by smtp.gmail.com with ESMTPSA id x8-20020aa79188000000b005dc70330d9bsm10009545pfa.26.2023.03.08.18.33.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Mar 2023 18:33:05 -0800 (PST) Message-ID: <060b2056-35c3-dbd3-e097-a53423737e45@shopee.com> Date: Thu, 9 Mar 2023 10:33:02 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH] mm: remove redundant check in handle_mm_fault To: David Hildenbrand , Matthew Wilcox Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230306024959.131468-1-haifeng.xu@shopee.com> <354360d5-dce6-a11c-ee61-d41e615bfa05@shopee.com> <6df72872-2829-47ab-552c-7ef8a6470e6f@shopee.com> <562e9cc3-d0aa-23e9-bd19-266b5aef2ae7@redhat.com> From: Haifeng Xu In-Reply-To: <562e9cc3-d0aa-23e9-bd19-266b5aef2ae7@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: py4e8htz4ikw3obxtc343zrgz6n6fxcu X-Rspamd-Queue-Id: 74E0D40004 X-HE-Tag: 1678329187-107866 X-HE-Meta: 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 GXr7DIW8 7JWbqOLuyGvD+4nW/SWuk5y+YCL5Z3zPHi59RwOvrMXvt8nHmsG3GId3qAj+p3jjp+Isqr49L0fu2p4gUqGYjIS4uQ0lWg8hwXts1kTFEA3dlA1ARdjySW3tEj6p6VqMwT7tRBeF0sria2faZd3U93Z+ytd/WS+xqPDpa+62QJwz6hxReqPKwJ9W1dvA7DXMWEWhFRnDnAMwz5ERTvl22W9bqaAEEN5woFG5rPWwFSQaVHuCF6krpRxplXxEh1aNlMjfkEJB+TpcxQoC3ooZijRgjeme7iQLLg3KZzvtou4j504XKbrvt/W2tsDJ4ILXq2vs1THs0mo9PolmjR7XTWkO58gHdG8HO/K1oPiuySzszZA1kd4bl7H+P4t15oMKgTFZznlZj6i+eTkbozN/b0MWiqa4levQ9DosBuDBk6PPcf4U= 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 2023/3/8 17:13, David Hildenbrand wrote: > On 08.03.23 10:03, Haifeng Xu wrote: >> >> >> On 2023/3/7 10:48, Matthew Wilcox wrote: >>> On Tue, Mar 07, 2023 at 10:36:55AM +0800, Haifeng Xu wrote: >>>> On 2023/3/6 21:49, David Hildenbrand wrote: >>>>> On 06.03.23 03:49, Haifeng Xu wrote: >>>>>> mem_cgroup_oom_synchronize() has checked whether current memcg_in_oom is >>>>>> set or not, so remove the check in handle_mm_fault(). >>>>> >>>>> "mem_cgroup_oom_synchronize() will returned immediately if memcg_in_oom is not set, so remove the check from handle_mm_fault()". >>>>> >>>>> However, that requires now always an indirect function call -- do we care about dropping that optimization? >>>>> >>>>> >>>> >>>> If memcg_in_oom is set, we will check it twice, one is from handle_mm_fault(), the other is from mem_cgroup_oom_synchronize(). That seems a bit redundant. >>>> >>>> if memcg_in_oom is not set, mem_cgroup_oom_synchronize() returns directly. Though it's an indirect function call, but the time spent can be negligible >>>> compare to the whole mm user falut preocess. And that won't cause stack overflow error. >>> >>> I suggest you measure it. >> >> test steps: >> 1) Run command: ./mmap_anon_test(global alloc, so the memcg_in_oom is not set) >> 2) Calculate the quotient of cost time and page-fault counts, run 10 rounds and average the results. >> >> The test result shows that whether using indirect function call or not, the time spent in user fault >> is almost the same, about 2.3ms. > > I guess most of the benchmark time is consumed by allocating fresh pages in your test (also, why exactly do you use MAP_SHARED?). Yes, most of the time consumption is page allocation. MAP_SHARED or MAP_PRIVATE doesn't affect the result，so I just use one of them at will, although no process share memory with it. > > Is 2.3ms the total time for writing to that 1GiB of memory or how did you derive that number? Posting both results would be cleaner (with more digits ;) ). > I'm sorry I got the measuring unit wrong，actually it is 2.3us for every page fault. The details are as follows. without change ------------------------------------------------------------------------------------------------- cost time(ms) number of page fault time of page faults(ns) 599 262144 2285 590 262144 2251 595 262144 2270 595 262144 2270 594 262144 2266 597 262144 2277 596 262144 2274 598 262144 2281 594 262144 2266 598 262144 2281 ------------------------------------------------------------------------------------------------- average: 2272 with change ------------------------------------------------------------------------------------------------- cost time(ms) number of page fault time of page faults(ns) 600 262144 2289 597 262144 2277 596 262144 2274 596 262144 2274 597 262144 2277 595 262144 2270 598 262144 2281 588 262144 2243 596 262144 2274 598 262144 2281 ------------------------------------------------------------------------------------------------- average: 2274