From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx159.postini.com [74.125.245.159]) by kanga.kvack.org (Postfix) with SMTP id 322146B0031 for ; Fri, 28 Jun 2013 14:55:51 -0400 (EDT) Received: by mail-pa0-f50.google.com with SMTP id fb1so2738545pad.23 for ; Fri, 28 Jun 2013 11:55:50 -0700 (PDT) Date: Fri, 28 Jun 2013 11:55:47 -0700 From: Anton Vorontsov 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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