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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FBB5C433F5 for ; Wed, 30 Mar 2022 01:59:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241784AbiC3CBl (ORCPT ); Tue, 29 Mar 2022 22:01:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236458AbiC3CBi (ORCPT ); Tue, 29 Mar 2022 22:01:38 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C3C76A438 for ; Tue, 29 Mar 2022 18:59:53 -0700 (PDT) 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > . >