From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: Preliminary Agenda and Activities for LSF Date: Tue, 29 Mar 2011 15:59:53 -0400 Message-ID: <20110329195953.GD21671@redhat.com> References: <1301373398.2590.20.camel@mulgrave.site> <4D91BF90.8070909@redhat.com> <20110329173338.GD24485@redhat.com> <20110329184501.GG24485@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: vgoyal@redhat.com, lsf@lists.linux-foundation.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, rwheeler@redhat.com, device-mapper development To: Shyam_Iyer@dell.com Return-path: Received: from mx1.redhat.com ([209.132.183.28]:7528 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754729Ab1C2UAC (ORCPT ); Tue, 29 Mar 2011 16:00:02 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Mar 29 2011 at 3:13pm -0400, Shyam_Iyer@dell.com wrote: > > > > Above is pretty generic. Do you have specific needs/ideas/concerns? > > > > > > > > Thanks > > > > Vivek > > > Yes.. if I limited by Ethernet b/w to 40% I don't need to limit I/O > > b/w via cgroups. Such bandwidth manipulations are network switch driven > > and cgroups never take care of these events from the Ethernet driver. > > > > So if IO is going over network and actual bandwidth control is taking > > place by throttling ethernet traffic then one does not have to specify > > block cgroup throttling policy and hence no need for cgroups to be > > worried > > about ethernet driver events? > > > > I think I am missing something here. > > > > Vivek > Well.. here is the catch.. example scenario.. > > - Two iSCSI I/O sessions emanating from Ethernet ports eth0, eth1 multipathed together. Let us say round-robin policy. > > - The cgroup profile is to limit I/O bandwidth to 40% of the multipathed I/O bandwidth. But the switch may have limited the I/O bandwidth to 40% for the corresponding vlan associated with one of the eth interface say eth1 > > The computation that the bandwidth configured is 40% of the available bandwidth is false in this case. What we need to do is possibly push more I/O through eth0 as it is allowed to run at 100% of bandwidth by the switch. > > Now this is a dynamic decision and multipathing layer should take care of it.. but it would need a hint.. No hint should be needed. Just use one of the newer multipath path selectors that are dynamic by design: "queue-length" or "service-time". This scenario is exactly what those path selectors are meant to address. Mike