From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751872AbcGRHWI (ORCPT ); Mon, 18 Jul 2016 03:22:08 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:37698 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751518AbcGRHWG (ORCPT ); Mon, 18 Jul 2016 03:22:06 -0400 Date: Mon, 18 Jul 2016 09:22:02 +0200 From: Michal Hocko To: Mikulas Patocka Cc: Ondrej Kozina , Jerome Marchand , Stanislav Kozina , linux-mm@kvack.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: System freezes after OOM Message-ID: <20160718072201.GC22671@dhcp22.suse.cz> References: <20160713111006.GF28723@dhcp22.suse.cz> <20160714125129.GA12289@dhcp22.suse.cz> <20160714145937.GB12289@dhcp22.suse.cz> <20160715083510.GD11811@dhcp22.suse.cz> <20160715122210.GG11811@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 15-07-16 13:02:17, Mikulas Patocka wrote: > > > On Fri, 15 Jul 2016, Michal Hocko wrote: > > > On Fri 15-07-16 08:11:22, Mikulas Patocka wrote: > > > > > > The stacktraces showed that the kcryptd process was throttled when it > > > tried to do mempool allocation. Mempool adds the __GFP_NORETRY flag to the > > > allocation, but unfortunatelly, this flag doesn't prevent the allocator > > > from throttling. > > > > Yes and in fact it shouldn't prevent any throttling. The flag merely > > says that the allocation should give up rather than retry > > reclaim/compaction again and again. > > > > > I say that the process doing mempool allocation shouldn't ever be > > > throttled. Maybe add __GFP_NOTHROTTLE? > > > > A specific gfp flag would be an option but we are slowly running out of > > bit space there and I am not yet convinced PF_LESS_THROTTLE is > > unsuitable. > > PF_LESS_THROTTLE will make it throttle less, but it doesn't eliminate > throttling entirely. So, maybe add PF_NO_THROTTLE? But PF_* flags are also > almost exhausted. I am not really sure we can make anybody so special to not throttle at all. Seeing a congested backig device sounds like a reasonable compromise. Besides that it seems that we do not really need to eliminate wait_iff_congested for dm to work properly again AFAIU. I plan to repost both patch today after some more internal review. If we need to do more changes I would suggest making them in separet patches. -- Michal Hocko SUSE Labs