From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [dm-devel] [Lsf-pc] [LSF/MM TOPIC] a few storage topics Date: Tue, 24 Jan 2012 11:56:31 -0500 Message-ID: <20120124165631.GA8941@infradead.org> References: <20120117213648.GA9457@quack.suse.cz> <20120118225808.GA3074@tux1.beaverton.ibm.com> <20120118232200.GA22019@quack.suse.cz> <4F1758D4.9010401@panasas.com> <20120119094637.GA23442@quack.suse.cz> <4F1BFF5F.6000502@panasas.com> <20120123161857.GC28526@quack.suse.cz> <20120123175353.GD30782@redhat.com> <20120124151504.GQ4387@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Chris Mason , Jeff Moyer , Andrea Arcangeli , Jan Kara , Boaz Harrosh , Mike Snitzer , linux-scsi@vger.kernel.org, neilb@suse.de, dm-devel@redhat.com, linux-fsdevel@vger.kernel.org, lsf-pc@lists.linux-foundation.org, "Darrick J. Wong" Return-path: Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:49069 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752038Ab2AXQ4k (ORCPT ); Tue, 24 Jan 2012 11:56:40 -0500 Content-Disposition: inline In-Reply-To: <20120124151504.GQ4387@shiny> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Jan 24, 2012 at 10:15:04AM -0500, Chris Mason wrote: > https://lkml.org/lkml/2011/12/13/326 > > This patch is another example, although for a slight different reason. > I really have no idea yet what the right answer is in a generic sense, > but you don't need a 512K request to see higher latencies from merging. That assumes the 512k requests is created by merging. We have enough workloads that create large I/O from the get go, and not splitting them and eventually merging them again would be a big win. E.g. I'm currently looking at a distributed block device which uses internal 4MB chunks, and increasing the maximum request size to that dramatically increases the read performance.