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=unavailable 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 3B721C433E7 for ; Fri, 16 Oct 2020 12:07:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C922C2084C 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" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407205AbgJPMHz (ORCPT ); Fri, 16 Oct 2020 08:07:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:43528 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407197AbgJPMHy (ORCPT ); Fri, 16 Oct 2020 08:07:54 -0400 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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