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 12F89CD5BAF for ; Fri, 22 May 2026 01:20:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8045B6B009E; Thu, 21 May 2026 21:20:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7DBA86B009F; Thu, 21 May 2026 21:20:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F1CF6B00A0; Thu, 21 May 2026 21:20:16 -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 5E0C06B009E for ; Thu, 21 May 2026 21:20:16 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 2E5701C1EC9 for ; Fri, 22 May 2026 01:20:16 +0000 (UTC) X-FDA: 84793300032.16.F0D186D Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) by imf23.hostedemail.com (Postfix) with ESMTP id 9D52514000B for ; Fri, 22 May 2026 01:20:14 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="jy/r4gRI"; spf=pass (imf23.hostedemail.com: domain of shakeel.butt@linux.dev designates 91.218.175.180 as permitted sender) smtp.mailfrom=shakeel.butt@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=1779412814; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=vHNkZOw2UW3I07VSJDEzsPCBLxzvWAd9K3Bgudx7KQM=; b=4YHdlReZkePkBHwu5/GLuv8Ix5pKD/Ngg5Ovt7KELu6TTGkEzagD/6fe+dpXE8iE2qYBmV r1R4z+CvED5tvgvUeqNBbNponGjwMx17DpUlSN5C+NusRP5jemTg64jE4ix/Hj6+qOhu4x HFjYb8iLu9QYygfDWjmruDHqJT2j1Mw= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="jy/r4gRI"; spf=pass (imf23.hostedemail.com: domain of shakeel.butt@linux.dev designates 91.218.175.180 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1779412814; a=rsa-sha256; cv=none; b=C5YWptww7hR+YeUJisc1LH+XklLHyvnoSe3vC9jYoYkHhZrUDHCzy7dfNxA7s1c0rLEuGx yBNb7oiD+qBCUBiDhhFRoPvByI5C3OY5e55d/i6nhx9uJLjaDNRA3CFwur3ZRVzYAS3dza PiuCqBYxryCoGkUfMJ0IMowkxXjbFb8= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779412813; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vHNkZOw2UW3I07VSJDEzsPCBLxzvWAd9K3Bgudx7KQM=; b=jy/r4gRIe+INC0fMlfJlaVAV5x+Nb+kKW1ZjbpReCKKEkZqCimx5YRDWT3Q3+hCVkcV9UX 2YgRNKrwM6EBzzzk6gUti1L+SEw9QMo2ynp9MTl9SL4EgNljClhgVgTeceWaHS2AmnOZWe xndOWTYnRO2WY7oCNwoD4m2/fxcPkao= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Qi Zheng , Alexandre Ghiti , Joshua Hahn , Harry Yoo , Meta kernel team , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot Subject: [PATCH v2 3/4] memcg: int16_t for cached slab stats Date: Thu, 21 May 2026 18:19:07 -0700 Message-ID: <20260522011908.1669332-4-shakeel.butt@linux.dev> In-Reply-To: <20260522011908.1669332-1-shakeel.butt@linux.dev> References: <20260522011908.1669332-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9D52514000B X-Stat-Signature: 5noshue8ikkrcoiwrdu3mbu93qa9ufyf X-HE-Tag: 1779412814-970118 X-HE-Meta: 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 be6fAMhk GPkaiZaY4C0FQbi+VDOHRNt1+A9QEMNgoGy8tYkH5RgMr+UC4qQ+sKPVPTJpPiWULP0SvwjGONZrTud0mCPOi1kICjnH4oI92ZQazHKw0QcbpAP1x+YmPy66S9eFQ6eDi7rn31wyPTomq5OFmBjZKACwaCKYcN4kZWsiNzdgmVvG9MK8oaUjehqTDHhTRKYyyGPJyoBsK37dbtfIa7nsGz5X7esW7wR4VPJaunNyh0L9v0/Ft8DzbIyS+PadtpHjtdPdEs1/HpvNdpZs8Re8dyRSU2dYecrSxMwJA4xylvnX+RylKnhd3LtuO+Kup1Lnq7ADbK2hYaG38mU0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently struct obj_stock_pcp stores cached slab stats in 'int' which is 4 bytes per counter on 64-bit machines. Switch them to int16_t to shrink the cached metadata. The existing PAGE_SIZE flush in __account_obj_stock() bounds *bytes at PAGE_SIZE on 4KiB and 16KiB page archs, well within int16_t. On 64KiB pages PAGE_SIZE is well above S16_MAX so that flush never fires, and a sufficiently long run of accumulations would overflow the cache. Add an explicit S16_MAX guard before each add: when the next add would push abs(*bytes) past S16_MAX, fold the cached value into @nr and flush directly via mod_objcg_mlstate() before the accumulation. Fixes: 01b9da291c49 ("mm: memcontrol: convert objcg to be per-memcg per-node type") Tested-by: kernel test robot Signed-off-by: Shakeel Butt Reviewed-by: Harry Yoo (Oracle) --- Changes since v2: - Collected tags mm/memcontrol.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e4f00a8159d5..78c02451312b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2022,8 +2022,8 @@ struct obj_stock_pcp { struct obj_cgroup *cached_objcg; uint16_t nr_bytes; int16_t node_id; - int nr_slab_reclaimable_b; - int nr_slab_unreclaimable_b; + int16_t nr_slab_reclaimable_b; + int16_t nr_slab_unreclaimable_b; struct work_struct work; unsigned long flags; @@ -3158,7 +3158,7 @@ static void __account_obj_stock(struct obj_cgroup *objcg, struct obj_stock_pcp *stock, int nr, struct pglist_data *pgdat, enum node_stat_item idx) { - int *bytes; + int16_t *bytes; /* * Though at the moment MAX_NUMNODES <= 1024 in all archs but let's make @@ -3195,6 +3195,16 @@ static void __account_obj_stock(struct obj_cgroup *objcg, bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b : &stock->nr_slab_unreclaimable_b; + /* + * To avoid overflow or underflow, flush directly if accumulating @nr + * would push the cached value past S16_MAX. + */ + if (abs(nr + *bytes) > S16_MAX) { + nr += *bytes; + *bytes = 0; + goto direct; + } + /* * Even for large object >= PAGE_SIZE, the vmstat data will still be * cached locally at least once before pushing it out. -- 2.53.0-Meta