Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754949Ab3F1OCJ (ORCPT ); Fri, 28 Jun 2013 10:02:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6685 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752566Ab3F1OCI (ORCPT ); Fri, 28 Jun 2013 10:02:08 -0400 Date: Fri, 28 Jun 2013 09:43:25 -0400 From: Luiz Capitulino To: Anton Vorontsov 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: <20130628094325.45f5139b@redhat.com> In-Reply-To: <20130628043411.GA9100@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> Organization: Red Hat 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 Content-Length: 2038 Lines: 43 On Thu, 27 Jun 2013 21:34:11 -0700 Anton Vorontsov wrote: > On Thu, Jun 27, 2013 at 06:13:53PM -0700, Andrew Morton wrote: > > On Thu, 27 Jun 2013 17:58:53 -0700 Anton Vorontsov wrote: > > > Current frequency is 1/(2MB). Suppose we ended up scanning the whole > > > memory on a 2GB host, this will give us 1024 hits. Doesn't feel too much* > > > to me... But for what it worth, I am against adding read() to the > > > interface -- just because we can avoid the unnecessary switch into the > > > kernel. > > > > What was it they said about premature optimization? > > > > I think I'd rather do nothing than add a mode hack (already!). > > > > The information Luiz wants is already available with the existing > > interface, so why not just use it until there is a real demonstrated > > problem? > > > > But all this does point at the fact that the chosen interface was not a > > good one. And it's happening so soon :( A far better interface would > > be to do away with this level filtering stuff in the kernel altogether. > > OK, I am convinced that modes might be not necessary, but I see no big > problem in current situation, 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. Agreed this is a good solution. > As one of the ways to change the interface, we can do the strict mode by > writing levels in uppercase, and warn_once on lowercase levels, describing > that the old behaviour will go away. Once (if ever) we remove the old > behaviour, the apps trying the old-style lowercase levels will fail > gracefully with EINVAL. Why don't we just break it? There's no non-development kernel released with this interface yet. -- 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/