From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754655Ab0DVQcS (ORCPT ); Thu, 22 Apr 2010 12:32:18 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:59043 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754180Ab0DVQcQ (ORCPT ); Thu, 22 Apr 2010 12:32:16 -0400 Date: Thu, 22 Apr 2010 12:32:11 -0400 From: Christoph Hellwig To: Nick Piggin Cc: Dave Chinner , linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Christoph Hellwig , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH 1/2] mm: add context argument to shrinker callback Message-ID: <20100422163211.GA2478@infradead.org> References: <1271118255-21070-1-git-send-email-david@fromorbit.com> <1271118255-21070-2-git-send-email-david@fromorbit.com> <20100418001514.GA26575@infradead.org> <20100419140039.GQ5683@laptop> <20100420004149.GA14744@dastard> <20100420083840.GR5683@laptop> <20100420103216.GK15130@dastard> <20100421084004.GS5683@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100421084004.GS5683@laptop> User-Agent: Mutt/1.5.19 (2009-01-05) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 21, 2010 at 06:40:04PM +1000, Nick Piggin wrote: > I'm saying that dynamic registration is no good, if we don't have a > way to order the shrinkers. We can happily throw in a priority field into the shrinker structure, but at this stage in the release process I'd rather have an as simple as possible fix for the regression. And just adding the context pointer which is a no-op for all existing shrinkers fits that scheme very well. If it makes you happier I can queue up a patch to add the priorities for 2.6.35. I think figuring out any meaningful priorities will be much harder than that, though. > > If a change of interface means that we end up with shorter call > > chains, less global state, more flexibilty, better batching and IO > > patterns, less duplication of code and algorithms and it doesn't > > cause any regressions, then where's the problem? > > Yep that would all be great but I don't see how the interface change > enables any of that at all. It seems to me that the advantage goes > the other way because it doesn't put as much crap into your mount > structure and you end up with an useful traversable list of mounts as > a side-effect. There really is not need for that. The Linux VFS is designed to have superblocks independent, which actually is a good thing as global state gets in the way of scalability or just clean code. Note that a mounts list would be even worse as filesystems basically are not concerned with mount points themselves.