Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755926Ab3F1Q51 (ORCPT ); Fri, 28 Jun 2013 12:57:27 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:42178 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859Ab3F1Q50 (ORCPT ); Fri, 28 Jun 2013 12:57:26 -0400 Date: Fri, 28 Jun 2013 09:57:22 -0700 From: Anton Vorontsov To: Luiz Capitulino Cc: Andrew Morton , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@suse.cz, kmpark@infradead.org, hyunhee.kim@samsung.com Subject: Re: [PATCH v2] vmpressure: implement strict mode Message-ID: <20130628165722.GA12271@teo> References: <20130626231712.4a7392a7@redhat.com> <20130627150231.2bc00e3efcd426c4beef894c@linux-foundation.org> <20130628000201.GB15637@bbox> <20130627173433.d0fc6ecd.akpm@linux-foundation.org> <20130628005852.GA8093@teo> <20130627181353.3d552e64.akpm@linux-foundation.org> <20130628043411.GA9100@teo> <20130628050712.GA10097@teo> <20130628100027.31504abe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20130628100027.31504abe@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1445 Lines: 30 On Fri, Jun 28, 2013 at 10:00:27AM -0400, Luiz Capitulino wrote: > On Thu, 27 Jun 2013 22:07:12 -0700 > Anton Vorontsov wrote: > > > On Thu, Jun 27, 2013 at 09:34:11PM -0700, Anton Vorontsov wrote: > > > ... we can add the strict mode and deprecate the > > > "filtering" -- basically we'll implement the idea of requiring that > > > userspace registers a separate fd for each level. > > > > Btw, assuming that more levels can be added, there will be a problem: > > imagine that an app hooked up onto low, med, crit levels in "strict" > > mode... then once we add a new level, the app will start missing the new > > level events. > > That's how it's expected to work, because on strict mode you're notified > for the level you registered for. So apps registering for critical, will > still be notified on critical just like before. Suppose you introduce a new level, and the system hits this level. Before, the app would receive at least some notification for the given memory load (i.e. one of the old levels), with the new level introduced in the kernel, the app will receive no events at all. This makes a serious behavioural change in the app (read: it'll break it). Anton -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/