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=-6.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS 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 4BA0AC4363A for ; Tue, 27 Oct 2020 19:07:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B382B206D4 for ; Tue, 27 Oct 2020 19:07:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="Aty8GcfN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1829404AbgJ0THT (ORCPT ); Tue, 27 Oct 2020 15:07:19 -0400 Received: from m12-17.163.com ([220.181.12.17]:34092 "EHLO m12-17.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2902408AbgJ0THT (ORCPT ); Tue, 27 Oct 2020 15:07:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=mEweC mt22E7HtZLqqnDVM3+F4KShMEJihMB8YkEVp50=; b=Aty8GcfNm5mnErMNWfpvk AJpcCL/5OAwhb7uzpxUqyCPZCVlTRsu6LuCRIZOJFAVBIQCZWLLHRbsiFMGCLvIs mYNAlAT8o0baSNbQUoOootlwSlAndmRyn4iQfYPDEc3xxpfA7eMur6h6shrjw8at ybgHgm7vMEfleU549XOLQU= Received: from localhost (unknown [101.86.209.121]) by smtp13 (Coremail) with SMTP id EcCowACXJRLJb5hf0bLkQA--.9970S2; Wed, 28 Oct 2020 03:06:49 +0800 (CST) Date: Wed, 28 Oct 2020 03:06:49 +0800 From: Hui Su To: Vlastimil Babka Cc: akpm@linux-foundation.org, gustavo@embeddedor.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/list_lru: optimize condition of exiting the loop Message-ID: <20201027190649.GA67829@rlk> References: <20201027170420.GA61326@rlk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CM-TRANSID: EcCowACXJRLJb5hf0bLkQA--.9970S2 X-Coremail-Antispam: 1Uf129KBjvdXoWrur43Aw1xuw4UKFy5Kw17KFg_yoWDArcE9r 9YvFn29a15CrWSgFsFgrn3ArZ5Wr48WFykJF9rJr1Dtry7Za4jg3ZxWF1DXrykWFWfXryU Xw18Ar18uw1UtjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7IU8fWrJUUUUU== X-Originating-IP: [101.86.209.121] X-CM-SenderInfo: xvkbvvri6rljoofrz/1tbiLgnKX1SIqoT7igAAsx Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 27, 2020 at 07:45:53PM +0100, Vlastimil Babka wrote: > On 10/27/20 6:04 PM, Hui Su wrote: > > In list_lru_walk(), nr_to_walk type is 'unsigned long', > > so nr_to_walk won't be '< 0'. > > > > In list_lru_walk_node(), nr_to_walk type is 'unsigned long', > > so *nr_to_walk won't be '< 0' too. > > > > We can use '!nr_to_walk' instead of 'nr_to_walk <= 0', which > > is more precise. > > > > Signed-off-by: Hui Su > > OK. Why not this too? > > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -294,7 +294,7 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid, > > isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg, > nr_to_walk); > - if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) { > + if (*nr_to_walk && list_lru_memcg_aware(lru)) { > for_each_memcg_cache_index(memcg_idx) { > struct list_lru_node *nlru = &lru->node[nid]; > > Thanks for your fast reply. I did not notice that, and i would add this to my change. I will resend PATCH V2, and cc to you. Thanks.