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 3D678C433EF for ; Wed, 30 Mar 2022 01:59:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AABC28D0002; Tue, 29 Mar 2022 21:59:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A0EFC8D0001; Tue, 29 Mar 2022 21:59:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 85FC98D0002; Tue, 29 Mar 2022 21:59:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0179.hostedemail.com [216.40.44.179]) by kanga.kvack.org (Postfix) with ESMTP id 7450C8D0001 for ; Tue, 29 Mar 2022 21:59:56 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0473E1828FDA9 for ; Wed, 30 Mar 2022 01:59:55 +0000 (UTC) X-FDA: 79299396792.16.AE18BD3 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf14.hostedemail.com (Postfix) with ESMTP id CC0A410000D for ; Wed, 30 Mar 2022 01:59:54 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KSqPL4pB3z1GD5x; Wed, 30 Mar 2022 09:59:34 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 30 Mar 2022 09:59:51 +0800 Subject: Re: [PATCH 4/8] mm/vmscan: save a bit of stack space in shrink_lruvec To: Christoph Hellwig CC: , , References: <20220329132619.18689-1-linmiaohe@huawei.com> <20220329132619.18689-5-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Wed, 30 Mar 2022 09:59:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Stat-Signature: 17isc4bjfpu9n9p4tpf3hwwgshbgoyg6 Authentication-Results: imf14.hostedemail.com; dkim=none; spf=pass (imf14.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CC0A410000D X-HE-Tag: 1648605594-764014 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/29 22:00, Christoph Hellwig wrote: > On Tue, Mar 29, 2022 at 09:26:15PM +0800, Miaohe Lin wrote: >> LRU_UNEVICTABLE is not taken into account when shrink lruvec. So we can >> save a bit of stack space by shrinking the array size of nr and targets >> to NR_LRU_LISTS - 1. No functional change intended. >> >> Signed-off-by: Miaohe Lin >> --- >> mm/vmscan.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index a6e60c78d058..ebd8ffb63673 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -2862,8 +2862,9 @@ static bool can_age_anon_pages(struct pglist_data *pgdat, >> >> static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) >> { >> - unsigned long nr[NR_LRU_LISTS]; >> - unsigned long targets[NR_LRU_LISTS]; >> + /* LRU_UNEVICTABLE is not taken into account. */ >> + unsigned long nr[NR_LRU_LISTS - 1]; >> + unsigned long targets[NR_LRU_LISTS - 1]; > > This looks like a problem waiting to happen.. IIUC, I am changing the array size to what it exactly uses now. And LRU_UNEVICTABLE won't be used anyway. Could you please tell me what kind of problem is waiting to happen ? If this will result in actual risk, I will drop this patch. Thanks. > > . >