From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vivek Goyal Subject: Re: dm-ioband + bio-cgroup benchmarks Date: Fri, 19 Sep 2008 09:12:04 -0400 Message-ID: <20080919131204.GB3606@redhat.com> References: <20080918.210418.226794540.ryov@valinux.co.jp> <20080918131554.GB20640@redhat.com> <20080919.151221.49666828.taka@valinux.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20080919.151221.49666828.taka@valinux.co.jp> Sender: linux-kernel-owner@vger.kernel.org To: Hirokazu Takahashi Cc: ryov@valinux.co.jp, linux-kernel@vger.kernel.org, dm-devel@redhat.com, containers@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xensource.com, fernando@oss.ntt.co.jp, balbir@linux.vnet.ibm.com, xemul@openvz.org, agk@sourceware.org, righi.andrea@gmail.com, jens.axboe@oracle.com List-Id: dm-devel.ids On Fri, Sep 19, 2008 at 03:12:21PM +0900, Hirokazu Takahashi wrote: > Hi, > > > > Hi All, > > > > > > I have got excellent results of dm-ioband, that controls the disk I/O > > > bandwidth even when it accepts delayed write requests. > > > > > > In this time, I ran some benchmarks with a high-end storage. The > > > reason was to avoid a performance bottleneck due to mechanical factors > > > such as seek time. > > > > > > You can see the details of the benchmarks at: > > > http://people.valinux.co.jp/~ryov/dm-ioband/hps/ > > > > > > > Hi Ryo, > > > > I had a query about dm-ioband patches. IIUC, dm-ioband patches will break > > the notion of process priority in CFQ because now dm-ioband device will > > hold the bio and issue these to lower layers later based on which bio's > > become ready. Hence actual bio submitting context might be different and > > because cfq derives the io_context from current task, it will be broken. > > This is completely another problem we have to solve. > The CFQ scheduler has really bad assumption that the current process > must be the owner. This problem occurs when you use some of device > mapper devices or use linux aio. > > > To mitigate that problem, we probably need to implement Fernando's > > suggestion of putting io_context pointer in bio. > > > > Have you already done something to solve this issue? > > Actually, I already have a patch to solve this problem, which make > each bio have a pointer to the io_context of the owner process. > Would you take a look at the thread whose subject is "I/O context > inheritance" in: > http://www.uwsg.iu.edu/hypermail/linux/kernel/0804.2/index.html#2850 > > Fernando also knows this. Great. Sure I will have a look at this thread. This is something we shall have to implement, irrespective of the fact whether we go for dm-ioband approach or an rb-tree per request queue approach. Thanks Vivek