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 X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 097F1C433DF for ; Fri, 16 Oct 2020 14:33:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B87A02084C for ; Fri, 16 Oct 2020 14:33:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408905AbgJPOdw convert rfc822-to-8bit (ORCPT ); Fri, 16 Oct 2020 10:33:52 -0400 Received: from smtp.h3c.com ([60.191.123.50]:14970 "EHLO h3cspam02-ex.h3c.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405999AbgJPOdw (ORCPT ); Fri, 16 Oct 2020 10:33:52 -0400 Received: from DAG2EX10-IDC.srv.huawei-3com.com ([10.8.0.73]) by h3cspam02-ex.h3c.com with ESMTPS id 09GEX97X045540 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 16 Oct 2020 22:33:09 +0800 (GMT-8) (envelope-from tian.xianting@h3c.com) Received: from DAG2EX03-BASE.srv.huawei-3com.com (10.8.0.66) by DAG2EX10-IDC.srv.huawei-3com.com (10.8.0.73) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 16 Oct 2020 22:33:13 +0800 Received: from DAG2EX03-BASE.srv.huawei-3com.com ([fe80::5d18:e01c:bbbd:c074]) by DAG2EX03-BASE.srv.huawei-3com.com ([fe80::5d18:e01c:bbbd:c074%7]) with mapi id 15.01.1713.004; Fri, 16 Oct 2020 22:33:13 +0800 From: Tianxianting To: Michal Hocko CC: "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] mm: vmscan: avoid a unnecessary reschedule in shrink_slab() Thread-Topic: [PATCH] mm: vmscan: avoid a unnecessary reschedule in shrink_slab() Thread-Index: AQHWo29cMaRbAMdQE0ycFn5GylDeeqmZnPOAgACJFdD//4YYAIAAiVZw//+CoICAAJNtUA== Date: Fri, 16 Oct 2020 14:33:13 +0000 Message-ID: References: <20201016033952.1924-1-tian.xianting@h3c.com> <20201016120749.GG22589@dhcp22.suse.cz> <9a2b772b13f84bdd9517b17d8d72aa89@h3c.com> <20201016130208.GI22589@dhcp22.suse.cz> <8a25eacf4b37460897911ade338754d3@h3c.com> <20201016134457.GM22589@dhcp22.suse.cz> In-Reply-To: <20201016134457.GM22589@dhcp22.suse.cz> Accept-Language: en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.99.141.128] x-sender-location: DAG2 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-DNSRBL: X-MAIL: h3cspam02-ex.h3c.com 09GEX97X045540 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for the explain. I got it. -----Original Message----- From: Michal Hocko [mailto:mhocko@suse.com] Sent: Friday, October 16, 2020 9:45 PM To: tianxianting (RD) Cc: akpm@linux-foundation.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: vmscan: avoid a unnecessary reschedule in shrink_slab() On Fri 16-10-20 13:20:41, Tianxianting wrote: > Thanks > I understood what you said :) > But whether it is proper to check reschedule in every loop when lock is taken? I do not see any actual problem TBH. cond_resched is mostly to increase interactivity for non preemptible kernel. It can reduce throughput but this is a memory reclaim path and I do not expect this to contribute to any moderate hot paths. Direct reclaim doesn't really count as a hot path. -- Michal Hocko SUSE Labs