From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754260Ab3F0WCd (ORCPT ); Thu, 27 Jun 2013 18:02:33 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39124 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753475Ab3F0WCc (ORCPT ); Thu, 27 Jun 2013 18:02:32 -0400 Date: Thu, 27 Jun 2013 15:02:31 -0700 From: Andrew Morton To: Luiz Capitulino Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@suse.cz, minchan@kernel.org, anton@enomsg.org, kmpark@infradead.org, hyunhee.kim@samsung.com Subject: Re: [PATCH v2] vmpressure: implement strict mode Message-Id: <20130627150231.2bc00e3efcd426c4beef894c@linux-foundation.org> In-Reply-To: <20130626231712.4a7392a7@redhat.com> References: <20130626231712.4a7392a7@redhat.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 26 Jun 2013 23:17:12 -0400 Luiz Capitulino wrote: > Currently, an eventfd is notified for the level it's registered for > _plus_ higher levels. > > This is a problem if an application wants to implement different > actions for different levels. For example, an application might want > to release 10% of its cache on level low, 50% on medium and 100% on > critical. To do this, an application has to register a different > eventfd for each pressure level. However, fd low is always going to > be notified and and all fds are going to be notified on level critical. > > Strict mode solves this problem by strictly notifiying an eventfd > for the pressure level it registered for. This new mode is optional, > by default we still notify eventfds on higher levels too. > It didn't take long for this simple interface to start getting ugly :( And having the fd operate in different modes is ugly. Can we instead pass the level in the event payload?