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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91684C5B572 for ; Wed, 12 Aug 2026 13:48:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5E77F6B016C; Wed, 12 Aug 2026 09:48:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5975D6B016D; Wed, 12 Aug 2026 09:48:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 488D36B016E; Wed, 12 Aug 2026 09:48:41 -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 211936B016C for ; Wed, 12 Aug 2026 09:48:41 -0400 (EDT) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B051416037B for ; Wed, 12 Aug 2026 13:48:40 +0000 (UTC) X-FDA: 85092747600.03.B211206 Received: from mta1.migadu.com (out-249.mta1.migadu.com [95.215.58.249]) by imf30.hostedemail.com (Postfix) with ESMTP id 97C3B80011 for ; Wed, 12 Aug 2026 13:48:38 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bqt6VLL2; spf=pass (imf30.hostedemail.com: domain of cui.tao@linux.dev designates 95.215.58.249 as permitted sender) smtp.mailfrom=cui.tao@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786542518; 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=yxJE5C6YtFE0Ee+SEe2FvdZ5LddPaUuMhy07fXctXXI=; b=7i9gjvCmrj4Kf9CYphuyTxSe8vf2ARMy1qaOBSRnkBOiyXA9+dUSueQEIsb7H32ogB7FCB 7vkW6ZK/oCSnzVU0qgbhhtnSa1/oim5FHY9CF2rVQjlekWhwVBrL+UjfLnV6XURJRbuZVr +G5bIf0w6F2IrHMzqXWGMmPXdV27XEc= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786542518; b=XYontf64F16sJ7DPpa6VSPbEi0HP3G3KS2QkWfw/Cx885OpOuaar3/8mjLR5tShA7jknY6 GsNear3Nv4GvfMiJiDvBOfTZ7xGtr/VePKyWPPOKVfjq9Cwqoyzx425Ew453OfXGRK0sSb D3Is0dAgllgt1frtmizCDpwnkfKFnZA= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bqt6VLL2; spf=pass (imf30.hostedemail.com: domain of cui.tao@linux.dev designates 95.215.58.249 as permitted sender) smtp.mailfrom=cui.tao@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Envelope-To: linux-mm@kvack.org DKIM-Signature: a=rsa-sha256; bh=ASMCgRYWFh1U8hGKVOolQ/aTQ/PK231J3u3FwxsWacs=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1786542517; v=1; x=1787147317; b=bqt6VLL2oPMWtajSw0sxl/NU0Mo2Oiu8rit8fZeSxMtlJERaEfHNKZKZGumb5o1F/v0QRCK2 qUUzXNLihvi8GGJFN+FA5creF05Y21skfBl4r/uq1Rk1GluMrGOYCYW47E7+tLQu4EMtBrQmm9x 8hNvs/6pH89NGSVYK7fZ3GIY= X-Envelope-To: linux-mm@kvack.org Received: from [192.168.1.116] (111.162.215.50) by smtp.migadu.com with ESMTPS id 18dd0f5011e94cb8; Wed, 12 Aug 2026 13:48:37 +0000 X-Migadu-Flow: FLOW_OUT Message-ID: <3ab5e2cb-0660-4b20-9e67-cb47e17ae554@linux.dev> Date: Wed, 12 Aug 2026 21:48:26 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: cui.tao@linux.dev, Michal Hocko , Shakeel Butt , Muchun Song , Harry Yoo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Guopeng Zhang , Ran Xiaokai Subject: Re: [PATCH] mm: memcg: fix slab over-accounting for in-object objcg metadata To: Guopeng Zhang , Johannes Weiner , Roman Gushchin , Vlastimil Babka , Andrew Morton References: <20260812124858.73487-1-guopeng.zhang@linux.dev> From: Tao Cui In-Reply-To: <20260812124858.73487-1-guopeng.zhang@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: sdnoeegqfj4faejoxq6hwz89j6qcpzrd X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 97C3B80011 X-HE-Tag: 1786542518-158702 X-HE-Meta: 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 J2legl37 51zAkRqHpU+Uv11VHvZV7LIZuG4yMYC/48nHPnJJzjIagQRO0eYatuR67N+KjVY8lcJdXLgaKx8TYVfa4ttjSsZTqWF09mFFrWZM/qsQJkLbd6AIge8Gx3j0qLmT36Pg6G28J9oCWJ5ExdgPolOa9lOqlH3+UEjYNQTAEPfHf3AOM9mSzDuAgpOHc7YngPdGY29fQAZQWUXHyy4akGg0J7aypdKGH8Sfi59OKh06jG26qlkG2wGIuG/NyFbBAFzeWdSHyYyPDQgoZudu0zpJN9HgCx2J+q81/WDaHQvqfIbFlbG0c5KXnnPvTZWpTLG61uSUus8DzvtkCXx7nEvG+zAFB4ARej9bysaEDOS5WbQ8VTdm3QbZsWxfDc/SeNMwDNv8rl1Mar2AbSawNQ9M+Tiw+AQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/8/12 20:48, Guopeng Zhang 写道: > From: Guopeng Zhang > > obj_full_size() adds the size of an obj_cgroup pointer to s->size to > account for slabobj_ext storage, which normally resides outside the > object. > > Since commit a77d6d338685 ("mm/slab: place slabobj_ext metadata in > unused space within s->size"), slabobj_ext can reside in object padding > already covered by s->size. The extra charge then accounts for the same > memory twice. > > The per-slab obj_exts_in_object bit introduced by commit b5bc35ace2c5 > ("mm/slab: replace slab.stride with obj_exts_in_object") identifies this > layout. Use it to omit the extra charge only for in-object metadata. > Unlike in-object metadata, slab-leftover and separately allocated metadata > are not covered by the per-object s->size charge, so retain the existing > charge for those cases. > > Reported-by: Ran Xiaokai > Link: https://lore.kernel.org/all/20260310113804.245647-1-ranxiaokai627@163.com/ > Fixes: a77d6d338685 ("mm/slab: place slabobj_ext metadata in unused space within s->size") > Signed-off-by: Guopeng Zhang > --- > mm/memcontrol.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index d1312441a02b..aef480f46891 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3526,12 +3526,16 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size) > refill_obj_stock(objcg, size, true); > } > > -static inline size_t obj_full_size(struct kmem_cache *s) > +static inline size_t obj_full_size(struct kmem_cache *s, struct slab *slab) > { > /* > * For each accounted object there is an extra space which is used > - * to store obj_cgroup membership. Charge it too. > + * to store obj_cgroup membership. Charge it too, unless it is stored > + * in object padding already covered by s->size. > */ > + if (obj_exts_in_object(slab)) > + return s->size; > + > return s->size + sizeof(struct obj_cgroup *); > } > > @@ -3539,7 +3543,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, > gfp_t flags, unsigned int slab_alloc_flags, > size_t size, void **p) > { > - size_t obj_size = obj_full_size(s); > struct obj_cgroup *objcg; > struct slab *slab; > size_t i; > @@ -3580,6 +3583,7 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, > unsigned long obj_exts; > struct slabobj_ext *obj_ext; > struct obj_stock_pcp *stock; > + size_t obj_size; > > slab = virt_to_slab(p[i]); > > @@ -3590,6 +3594,8 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, > continue; > } > > + obj_size = obj_full_size(s, slab); > + > /* > * if we fail and size is 1, memcg_alloc_abort_single() will > * just free the object, which is ok as we have not assigned > @@ -3632,7 +3638,7 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, > void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, > void **p, int objects, unsigned long obj_exts) > { > - size_t obj_size = obj_full_size(s); > + size_t obj_size = obj_full_size(s, slab); > > for (int i = 0; i < objects; i++) { > struct obj_cgroup *objcg; > > base-commit: e7f630142df2afccce90555e4972e60008222311 Reviewed-by: Tao Cui