Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757407Ab0FOKqK (ORCPT ); Tue, 15 Jun 2010 06:46:10 -0400 Received: from corega.com.ru ([195.178.208.66]:50366 "EHLO tservice.net.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757049Ab0FOKqH (ORCPT ); Tue, 15 Jun 2010 06:46:07 -0400 X-Greylist: delayed 1063 seconds by postgrey-1.27 at vger.kernel.org; Tue, 15 Jun 2010 06:46:07 EDT Date: Tue, 15 Jun 2010 14:28:22 +0400 From: Evgeniy Polyakov To: Dave Chinner Cc: Andrew Morton , Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Chris Mason , Nick Piggin , Rik van Riel , Johannes Weiner , Christoph Hellwig , KAMEZAWA Hiroyuki Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch Message-ID: <20100615102822.GA4010@ioremap.net> References: <1276514273-27693-1-git-send-email-mel@csn.ul.ie> <1276514273-27693-12-git-send-email-mel@csn.ul.ie> <20100614231144.GG6590@dastard> <20100614162143.04783749.akpm@linux-foundation.org> <20100615003943.GK6590@dastard> <20100614183957.ad0cdb58.akpm@linux-foundation.org> <20100615032034.GR6590@dastard> <20100614211515.dd9880dc.akpm@linux-foundation.org> <20100615063643.GS6590@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100615063643.GS6590@dastard> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1593 Lines: 37 On Tue, Jun 15, 2010 at 04:36:43PM +1000, Dave Chinner (david@fromorbit.com) wrote: > > Nope. Large-number-of-small-files is a pretty common case. If the fs > > doesn't handle that well (ie: by placing them nearby on disk), it's > > borked. > > Filesystems already handle this case just fine as we see it from > writeback all the time. Untarring a kernel is a good example of > this... > > I suggested sorting all the IO to be issued into per-mapping page > groups because: > a) makes IO issued from reclaim look almost exactly the same > to the filesytem as if writeback is pushing out the IO. > b) it looks to be a trivial addition to the new code. > > To me that's a no-brainer. That doesn't coverup large-number-of-small-files pattern, since untarring subsequently means creating something new, which FS can optimize. Much more interesting case is when we have dirtied large number of small files in kind-of random order and submitted them down to disk. Per-mapping sorting will not do anything good in this case, even if files were previously created in a good facion being placed closely and so on, and only block layer will find a correlation between adjacent blocks in different files. But with existing queue management it has quite a small opportunity, and that's what I think Andrew is arguing about. -- Evgeniy Polyakov -- 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/