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 503A2C25B75 for ; Thu, 23 May 2024 05:53:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A415B6B0083; Thu, 23 May 2024 01:53:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9F13F6B0088; Thu, 23 May 2024 01:53:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8B88A6B0089; Thu, 23 May 2024 01:53:39 -0400 (EDT) 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 6EA2B6B0083 for ; Thu, 23 May 2024 01:53:39 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id DF0771A02EE for ; Thu, 23 May 2024 05:53:38 +0000 (UTC) X-FDA: 82148593716.15.98DC995 Received: from mail-ej1-f50.google.com (mail-ej1-f50.google.com [209.85.218.50]) by imf25.hostedemail.com (Postfix) with ESMTP id 093C2A000C for ; Thu, 23 May 2024 05:53:36 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="b/FQALCB"; spf=pass (imf25.hostedemail.com: domain of yosryahmed@google.com designates 209.85.218.50 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=1716443617; 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=/NE4Ia1OfNQ96VRogomKZai/04wbpvQ4U9VVM90Atwk=; b=uV1xUab09l3U0SQAJ/CrG1u0VJHOI+fvTfNv0uEZaTz8TH6C4GvjSSrvBZtcS+tq5ac3mj GQ100wzMFK/+Vk1MVtXgYzorGZurspppOEwIod4NA7pDs/z3BEVvXEjVSVX6NQTf7z/bfr y/oUUypotupyLMWEZL/vvGhx6vTS+dM= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="b/FQALCB"; spf=pass (imf25.hostedemail.com: domain of yosryahmed@google.com designates 209.85.218.50 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=1716443617; a=rsa-sha256; cv=none; b=ROz4xx+TgL6fKTTDDrk/WYbEMgfX2ZNK1z6B4TxQ2hdbA/nwt243YJud+Z5b4zTjoFWKlq Nqfxr7l17P8WDBgSECvBTs0wmrVI4Fy0sKxGiMWF5te7nGU5Ahhw0FQ8xR9GSw9BtHK7t6 E1J0CAp54kSFim8YDdGrweOAgoToTEI= Received: by mail-ej1-f50.google.com with SMTP id a640c23a62f3a-a5a5cb0e6b7so1103962866b.1 for ; Wed, 22 May 2024 22:53:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1716443615; x=1717048415; 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=/NE4Ia1OfNQ96VRogomKZai/04wbpvQ4U9VVM90Atwk=; b=b/FQALCBEd8PTBBnnk1fZfl6ddu5ZiH+FW5Hhr9LSwYLw2viAKo9nZXW+Zd+OJ9uh5 ahG/6s+nndjp+8Jp/rqr/o7P9nVJn4buVMihSIwOsVE5FyVynYzDUrrWglDe7ORVvb2/ QDABFBiaBUN4d1Qsij5PsnqXe6ZLzwRM1cJhIsXsNiEaq7idcAAsbNr78lOIrTKYU9+Z v/I8EcqEW0T/N9lDpEq2BDt9awwQtMw6WX967dictShL1NatwHTHKb4CKTrY4O9LYzAo CBe1iIeqqdlFMLaA4metz0onzRiQOeh2/v0+lLvih2KDCJdIQo1rgn7L7EuYFBf/DUzX vuGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1716443615; x=1717048415; 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=/NE4Ia1OfNQ96VRogomKZai/04wbpvQ4U9VVM90Atwk=; b=mGQJaz/WAtPJB+UL3AA2HDVLm1hMVn1bi4PHekzrXxhzJp6ceAZfeYLkPa6YxRxa8e iNcRN1fo8c2SAdxptqj8UwTuK44/2A2r77lj2W7swcm4Gcg6P3sTx2Pm8fJ8og/qVZE+ M9HZI7jvC6cAwMcT4jbPDptLCqTpTDWfmMRF86fgvOw9l0c0HIezq3UfM/9WhZkFwgeM z1c62zWnMBDNZvOPMiwqU5ed/96i+8cjDD/5F8jFqi45iNPiLSm6EfBTy+6ia/JVd+Jm hhiWdlIOusAHt6WzC9CnE8y8Q87Gvt/3K7B/jdXn8J/TeIAUeJh4Hpql05l0q14dIVfT 5F2A== X-Forwarded-Encrypted: i=1; AJvYcCUYJUnAm7kGTYmXudSvNjH1eUiw0KQklLPjYC8GzbgUphg02DakSO9ALS7rCQ4VL+LqSZ1KgE7YnUx2uf3FshbmdQQ= X-Gm-Message-State: AOJu0YxEGLZjbaVHSo9qMaOdfN14QD+Xd98Gc72rcEfifB2u/16rbaaB qtjVGQglJGrEWepbmdS0o3T1KTic7PxJ04fINm/XEt0IhA0mUZozMFiT+OJErDlY5gR9Dr/CG2A ZWluzTgYiZGU9MkvRid4DCBnLYbHjR5qem6jW X-Google-Smtp-Source: AGHT+IFRCEo0DSlUwuM9NVea1wb5doYjdeL4viv68jGc9TuZBAXigzRYsnoWu4zchKZ8TYpXIcX7MoZR9CHLoPoSDj8= X-Received: by 2002:a17:906:fb04:b0:a59:a0c1:2624 with SMTP id a640c23a62f3a-a62280a0833mr246971666b.39.1716443615264; Wed, 22 May 2024 22:53:35 -0700 (PDT) MIME-Version: 1.0 References: <20240523034824.1255719-1-shakeel.butt@linux.dev> In-Reply-To: From: Yosry Ahmed Date: Wed, 22 May 2024 22:52:56 -0700 Message-ID: Subject: Re: [PATCH] memcg: rearrage fields of mem_cgroup_per_node To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com, oliver.sang@intel.com, kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 093C2A000C X-Stat-Signature: fqbkqtpwghbj3yseg6jo7e61adikqiep X-Rspam-User: X-HE-Tag: 1716443616-1611 X-HE-Meta: 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 16DFGmMw Gc2ZYupjW66HP0DyYKEKIpfGXausPtBk/jzTQdf0mCdQIkFpwoNg3Za14tUZsp2pv6sEZF1akC3oaxCHBLUnvxo2OCkuCMZSyOCJtTWsde56PH/Zid0EhWXKdunMVYSolPnKEq8vPh/DrTS4wxaMEknu2p2FJAaEmCTlkcqsdQD8jqhsHffvI4jQewN8cxWRYmez3oKVrSJYJhyHe3HdKR9tPjFSP9CLu3c24tiw8OIxOHu4gZxxV5o52x9NpQyh9NNUs5PZeLABYBDsKBSoWvGqaaqbfeIHnOuOD4qj8xChuAto= X-Bogosity: Ham, tests=bogofilter, spamicity=0.002328, 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, May 22, 2024 at 10:34=E2=80=AFPM Shakeel Butt wrote: > > On Wed, May 22, 2024 at 09:35:57PM -0700, Yosry Ahmed wrote: > > On Wed, May 22, 2024 at 8:48=E2=80=AFPM Shakeel Butt wrote: > [...] > > > > > > struct mem_cgroup_per_node { > > > - struct lruvec lruvec; > > > + /* Keep the read-only fields at the start */ > > > + struct mem_cgroup *memcg; /* Back pointer, we c= annot */ > > > + /* use container_of = */ > > > > > > struct lruvec_stats_percpu __percpu *lruvec_stats_percpu; > > > struct lruvec_stats *lruvec_stats; > > > - > > > - unsigned long lru_zone_size[MAX_NR_ZONES][NR_LRU_LI= STS]; > > > - > > > - struct mem_cgroup_reclaim_iter iter; > > > - > > > struct shrinker_info __rcu *shrinker_info; > > > > > > + /* memcg-v1 only stuff in middle */ > > > + > > > struct rb_node tree_node; /* RB tree node */ > > > unsigned long usage_in_excess;/* Set to the value b= y which */ > > > /* the soft limit is = exceeded*/ > > > bool on_tree; > > > - struct mem_cgroup *memcg; /* Back pointer, we c= annot */ > > > - /* use container_of = */ > > > > Do we need CACHELINE_PADDING() here (or maybe make struct lruvec > > cache-aligned) to make sure the false cacheline sharing doesn't happen > > again with the fields below, or is the idea that the fields that get > > read in hot paths (memcg, lruvec_stats_percpu, lruvec_stats) are far > > at the top, and the memcg v1 elements in the middle act as a buffer? > > > > IOW, is sharing between the fields below and memcg v1 fields okay > > because they are not read in the hot path? If yes, I believe it's > > worth a comment. It can be easily missed if the memcg v1 soft limit is > > removed later for example. > > > > For 6.10, I wanted to keep the change simple and yes, the memcg v1 stuff > as a buffer between the pointers and lruvec/lru_zone_size fields. For Fair enough, could we update the comment to explicitly mention this? > 6.11 or later kernels, I am planning to use some asserts to make sure > these fields don't share a cacheline, so later when we remove the > v1-only stuff, the asserts will make sure we keep the separate cacheline > property intact. > Makes sense to me. With the comment update, feel free to add: Reviewed-by: Yosry Ahmed