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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 A13C6C433DF for ; Fri, 16 Oct 2020 12:07:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D376320866 for ; Fri, 16 Oct 2020 12:07:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="MsTJuYeF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D376320866 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C47CE900003; Fri, 16 Oct 2020 08:07:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BB398900002; Fri, 16 Oct 2020 08:07:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A4A09900003; Fri, 16 Oct 2020 08:07:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0201.hostedemail.com [216.40.44.201]) by kanga.kvack.org (Postfix) with ESMTP id 8841E900002 for ; Fri, 16 Oct 2020 08:07:55 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 4A1468249980 for ; Fri, 16 Oct 2020 12:07:55 +0000 (UTC) X-FDA: 77377664910.18.grape66_0814cb72721d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id 22C9C1025ABDC for ; Fri, 16 Oct 2020 12:07:55 +0000 (UTC) X-HE-Tag: grape66_0814cb72721d X-Filterd-Recvd-Size: 2458 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Fri, 16 Oct 2020 12:07:54 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1602850073; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aMvmrgpjMkX0xJOTXr8Pz+UkBkQEErVHRE0b+uty4jo=; b=MsTJuYeFBaY1lUdcdwkieCiuRiuoHH/KEexOXZihB/7wj6fcen0rY7ib52Q8Q9Vd+dsEmk /xagWKCpLyntf1KWzA+EwuUbRbMPqd4ABTRuAvoj2TqI0Muh7oPpZLre7+yc+Ab91dliAV RFNaoo1GdLos0vZygjYfSC83Q9IcmdI= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 785A6AD72; Fri, 16 Oct 2020 12:07:53 +0000 (UTC) Date: Fri, 16 Oct 2020 14:07:49 +0200 From: Michal Hocko To: Xianting Tian 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() Message-ID: <20201016120749.GG22589@dhcp22.suse.cz> References: <20201016033952.1924-1-tian.xianting@h3c.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201016033952.1924-1-tian.xianting@h3c.com> 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 Fri 16-10-20 11:39:52, Xianting Tian wrote: > In shrink_slab(), it directly goes to 'out' label only when it > can't get the lock of shrinker_rwsew. In this case, it doesn't > do the real work of shrinking slab, so we don't need trigger a > reschedule by cond_resched(). Your changelog doesn't explain why this is not needed or undesirable. Do you see any actual problem? The point of this code is to provide a deterministic scheduling point regardless of the shrinker_rwsew. > > Signed-off-by: Xianting Tian > --- > mm/vmscan.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 466fc3144..676e97b28 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -687,8 +687,9 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, > } > > up_read(&shrinker_rwsem); > -out: > + > cond_resched(); > +out: > return freed; > } > > -- > 2.17.1 > -- Michal Hocko SUSE Labs