From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755659AbaFKOLX (ORCPT ); Wed, 11 Jun 2014 10:11:23 -0400 Received: from cantor2.suse.de ([195.135.220.15]:56416 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbaFKOLV (ORCPT ); Wed, 11 Jun 2014 10:11:21 -0400 Date: Wed, 11 Jun 2014 16:11:17 +0200 From: Michal Hocko To: Tejun Heo Cc: Johannes Weiner , Greg Thelen , Hugh Dickins , Andrew Morton , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Michel Lespinasse , Roman Gushchin , LKML , linux-mm@kvack.org Subject: Re: [PATCH 2/2] memcg: Allow hard guarantee mode for low limit reclaim Message-ID: <20140611141117.GF4520@dhcp22.suse.cz> References: <20140606144421.GE26253@dhcp22.suse.cz> <1402066010-25901-1-git-send-email-mhocko@suse.cz> <1402066010-25901-2-git-send-email-mhocko@suse.cz> <20140610165756.GG2878@cmpxchg.org> <20140611075729.GA4520@dhcp22.suse.cz> <20140611123109.GA17777@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140611123109.GA17777@htj.dyndns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 11-06-14 08:31:09, Tejun Heo wrote: > Hello, Michal. > > On Wed, Jun 11, 2014 at 09:57:29AM +0200, Michal Hocko wrote: > > Is this the kind of symmetry Tejun is asking for and that would make > > change is Nack position? I am still not sure it satisfies his soft > > Yes, pretty much. What primarily bothered me was the soft/hard > guarantees being chosen by a toggle switch while the soft/hard limits > can be configured separately and combined. The last consensus at LSF was that there would be a knob which will distinguish hard/best effort behavior. The weaker semantic has strong usecases IMHO so I wanted to start with it and add a knob for the hard guarantee later when explicitly asked for. Going with min, low, high and hard makes more sense to me of course. > > guarantee objections from other email. > > I was wondering about the usefulness of "low" itself in isolation and I think it has more usecases than "min" from simply practical POV. OOM means a potential service down time and that is a no go. Optimistic isolation on the other hand adds an advantages of the isolation most of the time while not getting completely flat on an exception (be it misconfiguration or a corner case like mentioned during the discussion). That doesn't mean "min" is not useful. It definitely is, the category of usecases will be more specific though. > I still think it'd be less useful than "high", but as there seem to be > use cases which can be served with that and especially as a part of a > consistent control scheme, I have no objection. > > "low" definitely requires a notification mechanism tho. Would vmpressure notification be sufficient? That one is in place for any memcg which is reclaimed. Or are you thinking about something more like oom_control? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f169.google.com (mail-we0-f169.google.com [74.125.82.169]) by kanga.kvack.org (Postfix) with ESMTP id 79B736B0162 for ; Wed, 11 Jun 2014 10:11:27 -0400 (EDT) Received: by mail-we0-f169.google.com with SMTP id t60so3962113wes.0 for ; Wed, 11 Jun 2014 07:11:26 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id mc10si10294630wic.84.2014.06.11.07.11.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 11 Jun 2014 07:11:23 -0700 (PDT) Date: Wed, 11 Jun 2014 16:11:17 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] memcg: Allow hard guarantee mode for low limit reclaim Message-ID: <20140611141117.GF4520@dhcp22.suse.cz> References: <20140606144421.GE26253@dhcp22.suse.cz> <1402066010-25901-1-git-send-email-mhocko@suse.cz> <1402066010-25901-2-git-send-email-mhocko@suse.cz> <20140610165756.GG2878@cmpxchg.org> <20140611075729.GA4520@dhcp22.suse.cz> <20140611123109.GA17777@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140611123109.GA17777@htj.dyndns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Johannes Weiner , Greg Thelen , Hugh Dickins , Andrew Morton , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Michel Lespinasse , Roman Gushchin , LKML , linux-mm@kvack.org On Wed 11-06-14 08:31:09, Tejun Heo wrote: > Hello, Michal. > > On Wed, Jun 11, 2014 at 09:57:29AM +0200, Michal Hocko wrote: > > Is this the kind of symmetry Tejun is asking for and that would make > > change is Nack position? I am still not sure it satisfies his soft > > Yes, pretty much. What primarily bothered me was the soft/hard > guarantees being chosen by a toggle switch while the soft/hard limits > can be configured separately and combined. The last consensus at LSF was that there would be a knob which will distinguish hard/best effort behavior. The weaker semantic has strong usecases IMHO so I wanted to start with it and add a knob for the hard guarantee later when explicitly asked for. Going with min, low, high and hard makes more sense to me of course. > > guarantee objections from other email. > > I was wondering about the usefulness of "low" itself in isolation and I think it has more usecases than "min" from simply practical POV. OOM means a potential service down time and that is a no go. Optimistic isolation on the other hand adds an advantages of the isolation most of the time while not getting completely flat on an exception (be it misconfiguration or a corner case like mentioned during the discussion). That doesn't mean "min" is not useful. It definitely is, the category of usecases will be more specific though. > I still think it'd be less useful than "high", but as there seem to be > use cases which can be served with that and especially as a part of a > consistent control scheme, I have no objection. > > "low" definitely requires a notification mechanism tho. Would vmpressure notification be sufficient? That one is in place for any memcg which is reclaimed. Or are you thinking about something more like oom_control? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org