From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: IO scheduler based IO controller V10 Date: Mon, 28 Sep 2009 20:24:57 +0200 Message-ID: <1254162297.9820.54.camel__14138.3374612362$1254162519$gmane$org@marge.simson.net> References: <1253820332-10246-1-git-send-email-vgoyal@redhat.com> <4ABC28DE.7050809@datenparkplatz.de> <20090925202636.GC15007@redhat.com> <1253976676.7005.40.camel@marge.simson.net> <1254034500.7933.6.camel@marge.simson.net> <20090927164235.GA23126@kernel.dk> <1254075359.7354.66.camel@marge.simson.net> <1254110648.7683.3.camel@marge.simson.net> <20090928174809.GB3643@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090928174809.GB3643-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Vivek Goyal Cc: dhaval-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Jens Axboe , agk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org, jmarchan-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, fernando-gVGce1chcLdL9jVzuh4AOg@public.gmane.org, Ulrich Lukas , jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, fchecconi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, righi.andrea-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org List-Id: containers.vger.kernel.org On Mon, 2009-09-28 at 13:48 -0400, Vivek Goyal wrote: > Hmm.., so close to 25% reduction on average in completion time of konsole. > But this is in presece of writer. Does this help even in presence of 1 or > more sequential readers going? Dunno, I've only tested sequential writer. > So here latency seems to be coming from three sources. > > - Wait in CFQ before request is dispatched (only in case of competing seq readers). > - seek latencies > - latencies because of bigger requests are already dispatched to disk. > > So limiting the size of request will help with third factor but not with first > two factors and here seek latencies seem to be the biggest contributor. Yeah, seek latency seems to dominate. -Mike