From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752805AbeDRHKD (ORCPT ); Wed, 18 Apr 2018 03:10:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:35955 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022AbeDRHKC (ORCPT ); Wed, 18 Apr 2018 03:10:02 -0400 Date: Wed, 18 Apr 2018 09:09:58 +0200 From: Michal Hocko To: Matthew Wilcox Cc: Minchan Kim , Andrew Morton , LKML , linux-mm , Johannes Weiner , Vladimir Davydov Subject: Re: [PATCH] mm:memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create Message-ID: <20180418070958.GM17484@dhcp22.suse.cz> References: <20180418022912.248417-1-minchan@kernel.org> <20180418030824.GA7320@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180418030824.GA7320@bombadil.infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 17-04-18 20:08:24, Matthew Wilcox wrote: > On Wed, Apr 18, 2018 at 11:29:12AM +0900, Minchan Kim wrote: > > If there are heavy memory pressure, page allocation with __GFP_NOWAIT > > fails easily although it's order-0 request. > > I got below warning 9 times for normal boot. > > > > [ 17.072747] c0 0 : page allocation failure: order:0, mode:0x2200000(GFP_NOWAIT|__GFP_NOTRACK) > > > > Let's not make user scared. > > > > - cw = kmalloc(sizeof(*cw), GFP_NOWAIT); > > + cw = kmalloc(sizeof(*cw), GFP_NOWAIT | __GFP_NOWARN); > > if (!cw) > > Not arguing against this patch. But how many places do we want to use > GFP_NOWAIT without __GFP_NOWARN? Not many, and the few which do do this > seem like they simply haven't added it yet. Maybe this would be a good idea? > > -#define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) > +#define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM | __GFP_NOWARN) We have tried something like this in the past and Linus was strongly against. I do not have reference handy but his argument was that each __GFP_NOWARN should be explicit rather than implicit because it is a deliberate decision to make. -- Michal Hocko SUSE Labs