From nobody Thu Dec 18 07:10:29 2025 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9E9C18C38 for ; Wed, 1 May 2024 17:26:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714584391; cv=none; b=ixMNpbxQajp7wzjSeikhaA3pKXmCubng7LEsIbBEO59VlNv4gw8upS4RUEzJv2PKlQIwYICfSShdGM2RfRs460MKwf7S+UjP4ylsKsBc+7c9Ty7VcD/AofmlpckjumIXv/CSL2ghyJ+8XqpWCTHWjtJJ/h2hywHl95mvjPuJDoc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714584391; c=relaxed/simple; bh=bpoSOwCps3ekmNK8friHUBN0NbKjjhHpo4dFg6sHcXY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=C4/3QLn5OO/TEc7etRYmB8EGPrm3UNEw5Vmir9rDAoyOhmGAgef7FmnvSzaFEjoQ93xVaV2BQWadxOXsFi0BTw21dR1ZQrMeQyaNfDXlu4GNyVkFrUUppBMzw1xaJ2g0FExls4+47R7rqqP3kbsvxYluQ6/jLET6zi2z4XFfTn0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=tIfgRTnl; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="tIfgRTnl" 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=1714584387; 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=d5S9dkOJqha+rpI1CHtwyB9wbo4t9Wc2EBy5O17ehws=; b=tIfgRTnl/mhCgo0S97RFAXjLL/WVu5BE3Xyfq+9Mm73A1FvvUmiRo1lxo7b4Xy3VsjEWSv x7EoZ6cGnTqWTDf9G9b6HpQZYMpFZEEwHjoreUm7T9cMzcP9nw8sl2uOSArKJ1uG3TCahI /Jtd6f/SoU72qn5FtRtSozJCOvm6c/w= From: Shakeel Butt To: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Yosry Ahmed , "T . J . Mercier" Cc: kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 1/8] memcg: reduce memory size of mem_cgroup_events_index Date: Wed, 1 May 2024 10:26:10 -0700 Message-ID: <20240501172617.678560-2-shakeel.butt@linux.dev> In-Reply-To: <20240501172617.678560-1-shakeel.butt@linux.dev> References: <20240501172617.678560-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" mem_cgroup_events_index is a translation table to get the right index of the memcg relevant entry for the general vm_event_item. At the moment, it is defined as integer array. However on a typical system the max entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to use int as storage type of the array. For now just use int8_t as type and add a BUILD_BUG_ON(). Another benefit of this change is that the translation table fits in 2 cachelines while previously it would require 8 cachelines (assuming 64 bytes cacheline). Signed-off-by: Shakeel Butt Reviewed-by: Roman Gushchin Reviewed-by: Yosry Ahmed Reviewed-by: T.J. Mercier --- Changes since v3: - N/A mm/memcontrol.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 602ad5faad4d..c146187cda9c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -607,11 +607,13 @@ static const unsigned int memcg_vm_event_stat[] =3D { }; =20 #define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) -static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; +static int8_t mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; =20 static void init_memcg_events(void) { - int i; + int8_t i; + + BUILD_BUG_ON(NR_VM_EVENT_ITEMS >=3D S8_MAX); =20 for (i =3D 0; i < NR_MEMCG_EVENTS; ++i) mem_cgroup_events_index[memcg_vm_event_stat[i]] =3D i + 1; --=20 2.43.0