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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 29B54CA9EB9 for ; Wed, 23 Oct 2019 13:15:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A0E421A4A for ; Wed, 23 Oct 2019 13:15:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405605AbfJWNPT (ORCPT ); Wed, 23 Oct 2019 09:15:19 -0400 Received: from mx2.suse.de ([195.135.220.15]:35604 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730450AbfJWNPS (ORCPT ); Wed, 23 Oct 2019 09:15:18 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E45C7B2F5; Wed, 23 Oct 2019 13:15:16 +0000 (UTC) Date: Wed, 23 Oct 2019 14:15:14 +0100 From: Mel Gorman To: Michal Hocko Cc: Andrew Morton , Waiman Long , Johannes Weiner , Roman Gushchin , Vlastimil Babka , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [RFC PATCH 2/2] mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo Message-ID: <20191023131514.GC28938@suse.de> References: <20191023095607.GE3016@techsingularity.net> <20191023102737.32274-1-mhocko@kernel.org> <20191023102737.32274-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20191023102737.32274-3-mhocko@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 23, 2019 at 12:27:37PM +0200, Michal Hocko wrote: > From: Michal Hocko > > pagetypeinfo_showfree_print is called by zone->lock held in irq mode. > This is not really nice because it blocks both any interrupts on that > cpu and the page allocator. On large machines this might even trigger > the hard lockup detector. > > Considering the pagetypeinfo is a debugging tool we do not really need > exact numbers here. The primary reason to look at the outuput is to see > how pageblocks are spread among different migratetypes therefore putting > a bound on the number of pages on the free_list sounds like a reasonable > tradeoff. > > The new output will simply tell > [...] > Node 6, zone Normal, type Movable >100000 >100000 >100000 >100000 41019 31560 23996 10054 3229 983 648 > > instead of > Node 6, zone Normal, type Movable 399568 294127 221558 102119 41019 31560 23996 10054 3229 983 648 > > The limit has been chosen arbitrary and it is a subject of a future > change should there be a need for that. > > Suggested-by: Andrew Morton > Signed-off-by: Michal Hocko You could have used need_resched() instead of unconditionally dropping the lock but that's very minor for a proc file and it would allos a parallel allocation to go ahead so Acked-by: Mel Gorman -- Mel Gorman SUSE Labs