Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752839Ab3F1TKo (ORCPT ); Fri, 28 Jun 2013 15:10:44 -0400 Received: from mail-pb0-f42.google.com ([209.85.160.42]:52835 "EHLO mail-pb0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752222Ab3F1Szv (ORCPT ); Fri, 28 Jun 2013 14:55:51 -0400 Date: Fri, 28 Jun 2013 11:55:47 -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: <20130628185547.GA14520@teo> References: <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> <20130628165722.GA12271@teo> <20130628170917.GA12610@teo> <20130628144507.37d28ed9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20130628144507.37d28ed9@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: 1440 Lines: 42 On Fri, Jun 28, 2013 at 02:45:07PM -0400, Luiz Capitulino wrote: > On Fri, 28 Jun 2013 10:09:17 -0700 > Anton Vorontsov wrote: > > > So, I would now argue that the current scheme is perfectly OK and can do > > everything you can do with the "strict" one, > > I forgot commenting this bit. This is not true, because I don't want a > low fd to be notified on critical level. The current interface just > can't do that. Why can't you use poll() and demultiplex the events? Check if there is an event in the crit fd, and if there is, then just ignore all the rest. > However, it *is* possible to make non-strict work on strict if we make > strict default _and_ make reads on memory.pressure_level return > available events. Just do this on app initialization: > > for each event in memory.pressure_level; do > /* register eventfd to be notified on "event" */ > done This scheme registers "all" events. Here is more complicated case: Old kernels, pressure_level reads: low, med, crit The app just wants to listen for med level. New kernels, pressure_level reads: low, FOO, med, BAR, crit How would application decide which of FOO and BAR are ex-med levels? 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/