Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755154AbYHEG2Z (ORCPT ); Tue, 5 Aug 2008 02:28:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751287AbYHEG2S (ORCPT ); Tue, 5 Aug 2008 02:28:18 -0400 Received: from fms-01.valinux.co.jp ([210.128.90.1]:50596 "EHLO mail.valinux.co.jp" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751142AbYHEG2S (ORCPT ); Tue, 5 Aug 2008 02:28:18 -0400 Date: Tue, 05 Aug 2008 15:28:16 +0900 (JST) Message-Id: <20080805.152816.105502343.taka@valinux.co.jp> To: dave@linux.vnet.ibm.com Cc: righi.andrea@gmail.com, xen-devel@lists.xensource.com, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, agk@sourceware.org Subject: Re: Too many I/O controller patches From: Hirokazu Takahashi In-Reply-To: <1217883036.20260.137.camel@nimitz> References: <1217876521.20260.123.camel@nimitz> <48976A2A.9060600@gmail.com> <1217883036.20260.137.camel@nimitz> X-Mailer: Mew version 5.1.52 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2326 Lines: 52 Hi, > > >> But I'm not yet convinced that limiting the IO writes at the device > > >> mapper layer is the best solution. IMHO it would be better to throttle > > >> applications' writes when they're dirtying pages in the page cache (the > > >> io-throttle way), because when the IO requests arrive to the device > > >> mapper it's too late (we would only have a lot of dirty pages that are > > >> waiting to be flushed to the limited block devices, and maybe this could > > >> lead to OOM conditions). IOW dm-ioband is doing this at the wrong level > > >> (at least for my requirements). Ryo, correct me if I'm wrong or if I've > > >> not understood the dm-ioband approach. > > > > > > The avoid-lots-of-page-dirtying problem sounds like a hard one. But, if > > > you look at this in combination with the memory controller, they would > > > make a great team. > > > > > > The memory controller keeps you from dirtying more than your limit of > > > pages (and pinning too much memory) even if the dm layer is doing the > > > throttling and itself can't throttle the memory usage. > > > > mmh... but in this way we would just move the OOM inside the cgroup, > > that is a nice improvement, but the main problem is not resolved... > > > > A safer approach IMHO is to force the tasks to wait synchronously on > > each operation that directly or indirectly generates i/o. > > Fine in theory, hard in practice. :) > > I think the best we can hope for is to keep parity with what happens in > the rest of the kernel. We already have a problem today with people > mmap()'ing lots of memory and dirtying it all at once. Adding a i/o > bandwidth controller or a memory controller isn't really going to fix > that. I think it is outside the scope of the i/o (and memory) > controllers until we solve it generically, first. Yes, that's right. This should be solved. But there is a good thing when you use a memory controller. A problem occurred in a certain cgroup will be confined in its cgroup. I think this is a great point, don't you think? Thank you, Hirokazu Takahashi. -- 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/