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 64B71E7AD74 for ; Tue, 3 Oct 2023 15:54:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DF84A6B020B; Tue, 3 Oct 2023 11:54:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DA8BC8D007D; Tue, 3 Oct 2023 11:54:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C71498D0003; Tue, 3 Oct 2023 11:54:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id B91826B020B for ; Tue, 3 Oct 2023 11:54:09 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 956F2B357F for ; Tue, 3 Oct 2023 15:54:09 +0000 (UTC) X-FDA: 81304596618.21.643A09E Received: from mail-ed1-f43.google.com (mail-ed1-f43.google.com [209.85.208.43]) by imf24.hostedemail.com (Postfix) with ESMTP id 4A164180003 for ; Tue, 3 Oct 2023 15:54:06 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=YHVDTMbG; spf=pass (imf24.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.43 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1696348446; a=rsa-sha256; cv=none; b=BoSf7JZDrhflmtigfXXy4Ot6J/NmD3J9VBcbW8PgcPqwo5g489sFHJvmUzBo2hHzNuVa84 SzqV7l/4vLRwAUXY30tFOHRFaFdF5PhacBiY8D3pneYt/h78snLleBFAIuWTPbHHizlhnZ msBYKBo33SOvcUWduCdjnnpK9jat50w= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=YHVDTMbG; spf=pass (imf24.hostedemail.com: domain of yosryahmed@google.com designates 209.85.208.43 as permitted sender) smtp.mailfrom=yosryahmed@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1696348446; 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=Dxid03xXpcvsVqUaGgfhHGeyo+iLwB2wREvZPzja/s0=; b=4lH6z5+g1rlIhX3r5NBzD316njcCGxhFZ65EsxMTYC9QHVvlpya8GyC9j/2i6jAb/DW6/e YgZzwn455NkJv1HYitSlko/mmBzH4IwqvqGzbc8D3MYrX5COHQU6VFFCDoezsqDdJECKGG EmT2ewCx2Gv/3PP9/dgr4DtV0gkrd7o= Received: by mail-ed1-f43.google.com with SMTP id 4fb4d7f45d1cf-5230a22cfd1so1900757a12.1 for ; Tue, 03 Oct 2023 08:54:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1696348444; x=1696953244; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=Dxid03xXpcvsVqUaGgfhHGeyo+iLwB2wREvZPzja/s0=; b=YHVDTMbGG4ITaX0wWXf7pdt5KSItg0BJ6JwmFs8nNpho/jH5WVmaSVq6CcoKAIaSFZ 6duu0Xi3eVmEnAm3Ej2nJ9TAGgcTI0rEdrREhEyjeQj/ypJAIxOir0efXdwfsNJIFmby cL6d8ZskSz7XIF1g5NNl+8EPEA0DJAJKjF7YGHhGrEKEsh78Lt6+f5HUYcJwcEAlCzwh LRRYZmlpr/Ni6PS7IxNEA8AMc8X8nAPD03a5kxed8/BOl6bp7/1IQHeyTJTTitNVJC3t ibVHKpH+BcsMolMyxe/t1K1v1CGcclCmhbKBGanRoRXElw8/0VyuyZQxAV+l1F1fiD4x //Nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696348444; x=1696953244; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Dxid03xXpcvsVqUaGgfhHGeyo+iLwB2wREvZPzja/s0=; b=HZwmreEOmoZLmnf+R4FokR3DDvecQY1aVLxk97GqsqBFOrzSho8lxHuBlAW1oO4e3q KBeRs7mdu8HS0nyyxr/30Ba7cMgdASTtufjgy4+tYdJo/5/CQKRrPl/2HKrMFkJtcyuW /uxXYPg4TdT7bAfTCCGwwP2TyvBsfrQp4o8NyypV4yAXXG94Uaf95NnAX8a8mPgMjEne LmNZB7xFdMIxJ9njZbzjNpMKhzoy0p/4FZJ7kkZbFH7v7wHOwd8B358A4jv8HPcDs7qu cz/lDQULGPMzJxUGbna1Bz/JIhtYsSzlbVoqNOgUE5RbNFkI7Q6VKqnvXx6cSF5U0KHf 82Kg== X-Gm-Message-State: AOJu0Yyhku0/olm6Fp0tGDQq5CvwSAS4UzfXuv3VsLAdZ/xCm3q/eLXn 1ZUE+5+RzjRIFcq3CfXD0leuNbq7IyxVHbfEGnqoRA== X-Google-Smtp-Source: AGHT+IHT5P1GPrW7t7OawdrJlX/jyBMUXSn0g82xaLa6cpdViOSy68e02n41+YU+V9/BtYsN4Pccbt9P/9A27fZ4vl8= X-Received: by 2002:a17:906:738b:b0:9a2:86a:f9b7 with SMTP id f11-20020a170906738b00b009a2086af9b7mr12235071ejl.59.1696348444408; Tue, 03 Oct 2023 08:54:04 -0700 (PDT) MIME-Version: 1.0 References: <20230922175741.635002-1-yosryahmed@google.com> <20230922175741.635002-3-yosryahmed@google.com> <20231003131309.GD17012@cmpxchg.org> In-Reply-To: <20231003131309.GD17012@cmpxchg.org> From: Yosry Ahmed Date: Tue, 3 Oct 2023 08:53:25 -0700 Message-ID: Subject: Re: [PATCH v2 2/2] mm: memcg: normalize the value passed into memcg_rstat_updated() To: Johannes Weiner Cc: Andrew Morton , Shakeel Butt , Michal Hocko , Roman Gushchin , Muchun Song , =?UTF-8?Q?Michal_Koutn=C3=BD?= , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4A164180003 X-Stat-Signature: cp7ahuouqx6j8zkqjjornjdyaxjds49h X-Rspam-User: X-HE-Tag: 1696348446-762978 X-HE-Meta: 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 gjNEmFTo /qivR9pbpvYo/DIoxkPeuh9VAYRZrXAqZ6abBdrPPwIuw09lgayfTfHfVklj0blRxDsI1Q6/gdZbDo8WYknrf2X53Yut22Xl2C9jH9VTGrfLI+OptXlikK5Fx3DcRfDYJm4X3s+KCNIhQJ5dft+wqLT2yQueQuxFc26C/iQ0YXsMT0u0O/4il5Uajn1IpYuSEHewO7qAVgSTnw4oFKdfEoCNKk8W09UYgABXAgh8VHB/Pc57zX2NrSset8S0Ab9oZ/oDUDayYO15LOD6fl5b99o5vJDk02MSjpdbOTvhPJ1FsK6BPPtnFWTfmyeo1jL8ycwigEHwNWqtDpCtJhADvoeMWaN3HcT2zaL2M X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 3, 2023 at 6:13=E2=80=AFAM Johannes Weiner = wrote: > > On Fri, Sep 22, 2023 at 05:57:40PM +0000, Yosry Ahmed wrote: > > memcg_rstat_updated() uses the value of the state update to keep track > > of the magnitude of pending updates, so that we only do a stats flush > > when it's worth the work. Most values passed into memcg_rstat_updated() > > are in pages, however, a few of them are actually in bytes or KBs. > > > > To put this into perspective, a 512 byte slab allocation today would > > look the same as allocating 512 pages. This may result in premature > > flushes, which means unnecessary work and latency. > > Yikes. > > I'm somewhat less concerned about the performance as I am about the > variance in flushing cost that could be quite difficult to pinpoint. > IMO this is a correctness fix and a code cleanup, not a performance > thing. Agreed, the code right now has a subtle mistake. > > > Normalize all the state values passed into memcg_rstat_updated() to > > pages. Round up non-zero sub-page to 1 page, because > > memcg_rstat_updated() ignores 0 page updates. > > > > Fixes: 5b3be698a872 ("memcg: better bounds on the memcg stats updates") > > Signed-off-by: Yosry Ahmed > > Acked-by: Johannes Weiner Thanks for taking a look!