Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751394AbZIJO4Y (ORCPT ); Thu, 10 Sep 2009 10:56:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751149AbZIJO4Y (ORCPT ); Thu, 10 Sep 2009 10:56:24 -0400 Received: from casper.infradead.org ([85.118.1.10]:34590 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932AbZIJO4X (ORCPT ); Thu, 10 Sep 2009 10:56:23 -0400 Subject: Re: [RFC][PATCH 7/7] writeback: balance_dirty_pages() shall write more than dirtied pages From: Peter Zijlstra To: Wu Fengguang Cc: Chris Mason , Jan Kara , Andrew Morton , Jens Axboe , Dave Chinner , Christoph Hellwig , Artem Bityutskiy , LKML , "linux-fsdevel@vger.kernel.org" In-Reply-To: <20090910132154.GA6446@localhost> References: <20090909145141.293229693@intel.com> <20090909150601.159061863@intel.com> <20090909154413.GC7949@duck.suse.cz> <20090910014201.GB10957@localhost> <20090910125742.GH5106@think> <20090910132154.GA6446@localhost> Content-Type: text/plain Date: Thu, 10 Sep 2009 16:56:04 +0200 Message-Id: <1252594564.7205.36.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2082 Lines: 38 On Thu, 2009-09-10 at 21:21 +0800, Wu Fengguang wrote: > On Thu, Sep 10, 2009 at 08:57:42PM +0800, Chris Mason wrote: > > On Thu, Sep 10, 2009 at 09:42:01AM +0800, Wu Fengguang wrote: > > > On Wed, Sep 09, 2009 at 11:44:13PM +0800, Jan Kara wrote: > > > > On Wed 09-09-09 22:51:48, Wu Fengguang wrote: > > > > > Some filesystem may choose to write much more than ratelimit_pages > > > > > before calling balance_dirty_pages_ratelimited_nr(). So it is safer to > > > > > determine number to write based on real number of dirtied pages. > > > > > > > > > > The increased write_chunk may make the dirtier more bumpy. This is > > > > > filesystem writers' duty not to dirty too much at a time without > > > > > checking the ratelimit. > > > > I don't get this. balance_dirty_pages_ratelimited_nr() is called when we > > > > dirty the page, not when we write it out. So a problem would only happen if > > > > filesystem dirties pages by set_page_dirty() and won't call > > > > balance_dirty_pages_ratelimited_nr(). But e.g. generic_perform_write() > > > > and do_wp_page() takes care of that. So where's the problem? > > > > > > It seems that btrfs_file_write() is writing in chunks of up to 1024-pages > > > (1024 is the computed nrptrs value in a 32bit kernel). And it calls > > > balance_dirty_pages_ratelimited_nr() each time it dirtied such a chunk. > > > > I can easily change this to call more often, but we do always call > > balance_dirty_pages to reflect how much ram we've really sent down. > > Btrfs is doing OK. 2MB/4MB looks like reasonable chunk sizes. The > need-change part is balance_dirty_pages_ratelimited_nr(), hence this > patch :) I'm not getting it, it calls set_page_dirty() for each page, right? and then it calls into balance_dirty_pages_ratelimited_nr(), that sounds right. What is the problem with that? -- 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/