From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752664AbcEDTkX (ORCPT ); Wed, 4 May 2016 15:40:23 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:34400 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751423AbcEDTkW (ORCPT ); Wed, 4 May 2016 15:40:22 -0400 Date: Wed, 4 May 2016 21:40:19 +0200 From: Michal Hocko To: Joonsoo Kim Cc: Joonsoo Kim , Andrew Morton , Vlastimil Babka , Mel Gorman , Minchan Kim , Alexander Potapenko , Linux Memory Management List , LKML Subject: Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Message-ID: <20160504194019.GE21490@dhcp22.suse.cz> References: <1462252984-8524-1-git-send-email-iamjoonsoo.kim@lge.com> <1462252984-8524-7-git-send-email-iamjoonsoo.kim@lge.com> <20160503085356.GD28039@dhcp22.suse.cz> <20160504021449.GA10256@js1304-P5Q-DELUXE> <20160504092133.GG29978@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 05-05-16 00:30:35, Joonsoo Kim wrote: > 2016-05-04 18:21 GMT+09:00 Michal Hocko : [...] > > Do we really consume 512B of stack during reclaim. That sounds more than > > worrying to me. > > Hmm...I checked it by ./script/stackusage and result is as below. > > shrink_zone() 128 > shrink_zone_memcg() 248 > shrink_active_list() 176 > > We have a call path that shrink_zone() -> shrink_zone_memcg() -> > shrink_active_list(). > I'm not sure whether it is the deepest path or not. This is definitely not the deepest path. Slab shrinkers can take more but 512B is still a lot. Some call paths are already too deep when calling into the allocator and some of them already use GFP_NOFS to prevent from potentially deep callchain slab shrinkers. Anyway worth exploring for better solutions. And I believe it would be better to solve this in the stackdepot directly so other users do not have to invent their own ways around the same issue. I have just checked the code and set_track uses save_stack which does the same thing and it seems to be called from the slab allocator. I have missed this usage before so the problem already does exist. It would be unfair to request you to fix that in order to add a new user. It would be great if this got addressed though. -- Michal Hocko SUSE Labs