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 41342C36000 for ; Wed, 19 Mar 2025 17:35:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 50A56280003; Wed, 19 Mar 2025 13:35:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4BA2B280001; Wed, 19 Mar 2025 13:35:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 35BEA280003; Wed, 19 Mar 2025 13:35:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 04755280001 for ; Wed, 19 Mar 2025 13:35:40 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 11B831A0566 for ; Wed, 19 Mar 2025 17:35:41 +0000 (UTC) X-FDA: 83239002882.07.998A0A4 Received: from mail-qk1-f178.google.com (mail-qk1-f178.google.com [209.85.222.178]) by imf24.hostedemail.com (Postfix) with ESMTP id E37E2180004 for ; Wed, 19 Mar 2025 17:35:38 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=cmpxchg-org.20230601.gappssmtp.com header.s=20230601 header.b=MueCcBRO; spf=pass (imf24.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.222.178 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (policy=none) header.from=cmpxchg.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1742405739; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gGhGDuuhhwM0Ly0sNcJ9dpabn4WGi06NRVVNOwZFOBw=; b=F9O3MjCAB1AizEZmMSjgZ6QE8MAPKGVC+HuEO/ddpqvGnv/v6a8R+bZBjywAssKP0PWCVe 1FgSvYmrSVIsnWecUR9VZCT5SiwzdS8Im8BB5YQY4Bkw9hYJ+vl8sRvzIi4q97OLYKGoV5 nJrzlYz72nYuV3/BP2mwI9ph/cWohl4= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=cmpxchg-org.20230601.gappssmtp.com header.s=20230601 header.b=MueCcBRO; spf=pass (imf24.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.222.178 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (policy=none) header.from=cmpxchg.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1742405739; a=rsa-sha256; cv=none; b=7+WAAR3/ER0xo3O26o6KSQu1gSGaSwP7eS9FYQ1rwB922I4+wK/cqzWvTdgPsZ3op1XlTO 1I7m2abqfzyfCzFVyagguFV65pHtc3uRMsUzOHuLY/8buqaRNHGFV+dIn9tSapamkyLcY9 qEXM6snRYKotU5Pho3EmHTFSD7FpiU8= Received: by mail-qk1-f178.google.com with SMTP id af79cd13be357-7c559b3eb0bso403037085a.1 for ; Wed, 19 Mar 2025 10:35:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20230601.gappssmtp.com; s=20230601; t=1742405738; x=1743010538; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=gGhGDuuhhwM0Ly0sNcJ9dpabn4WGi06NRVVNOwZFOBw=; b=MueCcBROc2DAB/LkQ1mqePhAbgHDzFSnnz6a5e06Bil8JXHU3fsMvIv79Ea4RXsOLB R2LUb1TxbB7FKaIlf8GrW3BCtbKOlgvxZrCNVEodt4kVvF1moA0i2qyqEifYHBGUfKly 2F6cBPISfNW9FhEBmOXujWEJKZp1NbH7PV59hc9QtxC9WUKIpyqEPayWG3upMYIC6id8 RLRmfLB4WFqgRoOiDS789JjnTob8qFNYg02XAdvfbyev0vrbnhxFaFS9UMxT1w8jSwmm jAHDLZSsEix14zqe8xdIwUkKtEi4gPqUEtj7akCSsl0kjDl3Ee3hr5lOvV5glQe8EnqC 5syQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1742405738; x=1743010538; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gGhGDuuhhwM0Ly0sNcJ9dpabn4WGi06NRVVNOwZFOBw=; b=iKw11suBmOKCouLmp15G1Ddb0K2VgMkDTiZlDql3PjILF98yAgZSbo2XsEatfP825X Tw1rDnGiwQiW1jNhTWCfOsoNfpcmzYGDlqyefKZhY+8QGwq9ay47f1HWFa5Lk/I0dibE 400SRhNd2/rfB5ilmTWIqwEos6f8uQwLzOHg5c1AsQg+9jfJ30b/QwBYHCMovYkU0/O3 32KLC4SRwy6AYOLvQwi0e9nB8o7p7evNUJ+zTkczAjSGEEy/v06ZKelqtJmae+dk8nzL jIV95+QIydptOO/ArPp4O3ROT8Y+SanOkmepxyprVlKEUiKpaUCiv5UooK337bHVOsKf 6GIQ== X-Forwarded-Encrypted: i=1; AJvYcCVcosMfsdq9SuXzmKeDCopgaTOU+g9JjxStrZ4AnlIbgxQxF/sdagUinBXk+uRPG4i5kIHHjhUNhQ==@kvack.org X-Gm-Message-State: AOJu0YxaDJ52EbllwwhPkSjAKUYxeaQo/ACcaOpNo1sN+LuBKf446Agh Xri+2hLrI6sIlCLKWfqQ05rRbDFXxuvnT5qJOybFHzqhr4CnwWyN7r3mlR+s3j4= X-Gm-Gg: ASbGnct25ssgpsFnYcfImQdgypidh8BnrmiwbaMc0PYay8ZpFsfF+a9IyLkeQGfPY6V ILpqlgbdE7VJuP2klFyfUdgU+IDcrWFqDPT2fKU8Odf7VFjXnz/pBd//7OLJMc50lFThRE73UZ7 aSVzZ2UzhQL+zoT7ATNPYqV8gejl3ZuGfS2EkwDIGCKr4SnBTKT5ak7XJckRpZlKfFO//92pfok isZfS846BSau62N4F0VKNjDw4+wNcDz3CpHFasRVv8D6V3RZNneS2w+xpQ89/rj0EOoPEKaq11Y zRCtLRGbDUe4qWWq5Letc19zg52QLa+9vCf/mqWBVBQ= X-Google-Smtp-Source: AGHT+IFR0/DfY8PYnes84poP8QP06hXgfeFrcg01HIiFZ9sGfXEz2eMa/vjBdtqJwbnxBH9L/Po3Bw== X-Received: by 2002:a05:620a:25d1:b0:7c5:3b8d:9f37 with SMTP id af79cd13be357-7c5b0c9401bmr1747185a.30.1742405737601; Wed, 19 Mar 2025 10:35:37 -0700 (PDT) Received: from localhost ([2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with UTF8SMTPSA id af79cd13be357-7c5ad3b2908sm67625185a.88.2025.03.19.10.35.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Mar 2025 10:35:36 -0700 (PDT) Date: Wed, 19 Mar 2025 13:35:36 -0400 From: Johannes Weiner To: Greg Thelen Cc: Tejun Heo , Michal =?iso-8859-1?Q?Koutn=FD?= , Andrew Morton , Eric Dumazet , Yosry Ahmed , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Eric Dumazet Subject: Re: [PATCH] cgroup/rstat: avoid disabling irqs for O(num_cpu) Message-ID: <20250319173536.GB1876369@cmpxchg.org> References: <20250319071330.898763-1-gthelen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250319071330.898763-1-gthelen@google.com> X-Rspam-User: X-Rspamd-Queue-Id: E37E2180004 X-Rspamd-Server: rspam08 X-Stat-Signature: tqd49pceb6kbyxyymu9eo9d7amoc6h5k X-HE-Tag: 1742405738-814133 X-HE-Meta: U2FsdGVkX199UbvlF+tXFwp3SL9+yCFYOZ5LXrpDZBRMv22Ko9XuQbZPD/oYTgDHQAEf8gRlDQziJThFEssh7trzOi6eNAMOIdcfxWf5wkNONu7PKgfpc/JG0jKy87Z4ghOkMJOR50/ftV+CK9SfgPb3HHYgi8Y+WE//mltZuoBTa0mO/ksG1LO8pDZm+cvDG2tcLzqLhUR2p9EWQg0WsxZCc4ngldLh5RR4kSucgjZImLiM1FCGgMzeSDA2KePdezIiHimtIvcoEc7t4tmDqY7cd0aBV0bnDv9orYSz4LsveTlf0KZBJsOcXO6/uo1pyr2RGNnZsElGO4HR8q3bNUSYBuXSjGfslnurxCBJvM+zjrRSPRz9FmW9znn+OJN837Fi+7x4WUdXHecNalQUzVGEsyUYg2oBlE6PLBUsh9oVlQIp787td4AQyxnRfDLA5j2dJwoG2xMR9vefPeCavJmkgFHnZRVKusI082TK+DDoEyoelIYeKcYcYgsc8jpK3PGgkbk3mJuKBIoFjr0PbGrUB72ku462S+0x/u2PioBtnOnf7lDbMJLc7YlAmSPqWO3juI++ggRLfiFgnJuqsyBAAwdyiMKh6HpyfRirZ5pOARSiVTeGFsiHc4BRvcWvObR/Ppnb2Wy6wMiWnhOl/l09M2QYaMis3VU8jZeUbqlF9m5lSXQObbU2rl451Od6XrNUj8QEQku8wbfnwAL2I4hg74/79HLCdrLDaNcLWlnR/yM6EDqPs8kp3fScWcHGfZd1BsdX7589QEeNlxEFd/z0+IzXMfCF7DjUoCrBVdX8IqwpOsDdRp+K03jo7/S6e6g7WQehjXo5MfTdVMR0jXUVw04ru992tPAJxK7/ByYchM8/zRtyZqAvgWlbxn1ztpOeBHguVxnAmdvTTKT8tqNK28WVS7+J33mB8hkIS1V+lFXoPb0wbrOmuZBP4KUjsvZ/JWvgnQ4UpW8FwMI L1cx5uIW 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 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: List-Subscribe: List-Unsubscribe: On Wed, Mar 19, 2025 at 12:13:30AM -0700, Greg Thelen wrote: > From: Eric Dumazet > > cgroup_rstat_flush_locked() grabs the irq safe cgroup_rstat_lock while > iterating all possible cpus. It only drops the lock if there is > scheduler or spin lock contention. If neither, then interrupts can be > disabled for a long time. On large machines this can disable interrupts > for a long enough time to drop network packets. On 400+ CPU machines > I've seen interrupt disabled for over 40 msec. > > Prevent rstat from disabling interrupts while processing all possible > cpus. Instead drop and reacquire cgroup_rstat_lock for each cpu. This > approach was previously discussed in > https://lore.kernel.org/lkml/ZBz%2FV5a7%2F6PZeM7S@slm.duckdns.org/, > though this was in the context of an non-irq rstat spin lock. > > Benchmark this change with: > 1) a single stat_reader process with 400 threads, each reading a test > memcg's memory.stat repeatedly for 10 seconds. > 2) 400 memory hog processes running in the test memcg and repeatedly > charging memory until oom killed. Then they repeat charging and oom > killing. > > v6.14-rc6 with CONFIG_IRQSOFF_TRACER with stat_reader and hogs, finds > interrupts are disabled by rstat for 45341 usec: > # => started at: _raw_spin_lock_irq > # => ended at: cgroup_rstat_flush > # > # > # _------=> CPU# > # / _-----=> irqs-off/BH-disabled > # | / _----=> need-resched > # || / _---=> hardirq/softirq > # ||| / _--=> preempt-depth > # |||| / _-=> migrate-disable > # ||||| / delay > # cmd pid |||||| time | caller > # \ / |||||| \ | / > stat_rea-96532 52d.... 0us*: _raw_spin_lock_irq > stat_rea-96532 52d.... 45342us : cgroup_rstat_flush > stat_rea-96532 52d.... 45342us : tracer_hardirqs_on <-cgroup_rstat_flush > stat_rea-96532 52d.... 45343us : > => memcg1_stat_format > => memory_stat_format > => memory_stat_show > => seq_read_iter > => vfs_read > => ksys_read > => do_syscall_64 > => entry_SYSCALL_64_after_hwframe > > With this patch the CONFIG_IRQSOFF_TRACER doesn't find rstat to be the > longest holder. The longest irqs-off holder has irqs disabled for > 4142 usec, a huge reduction from previous 45341 usec rstat finding. > > Running stat_reader memory.stat reader for 10 seconds: > - without memory hogs: 9.84M accesses => 12.7M accesses > - with memory hogs: 9.46M accesses => 11.1M accesses > The throughput of memory.stat access improves. > > The mode of memory.stat access latency after grouping by of 2 buckets: > - without memory hogs: 64 usec => 16 usec > - with memory hogs: 64 usec => 8 usec > The memory.stat latency improves. > > Signed-off-by: Eric Dumazet > Signed-off-by: Greg Thelen > Tested-by: Greg Thelen Acked-by: Johannes Weiner