Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755678Ab1CKQHn (ORCPT ); Fri, 11 Mar 2011 11:07:43 -0500 Received: from smtp-out.google.com ([216.239.44.51]:3234 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751091Ab1CKQHl (ORCPT ); Fri, 11 Mar 2011 11:07:41 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type; b=IvKdGS46qGqbqEZuYeKOg+VaWaxhp9Ld24c2S6FFvpMg1f5WEA2TXWsI9/uSk1udij RrMq9F3rpx3F3wsl2kvg== MIME-Version: 1.0 In-Reply-To: <20110311024732.GB11710@redhat.com> References: <1299619256-12661-1-git-send-email-teravest@google.com> <20110308224325.GK27455@redhat.com> <20110308225059.GL27455@redhat.com> <20110311024732.GB11710@redhat.com> From: Justin TerAvest Date: Fri, 11 Mar 2011 08:07:17 -0800 Message-ID: Subject: Re: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes. To: Vivek Goyal Cc: m-ikeda@ds.jp.nec.com, jaxboe@fusionio.com, linux-kernel@vger.kernel.org, ryov@valinux.co.jp, taka@valinux.co.jp, kamezawa.hiroyu@jp.fujitsu.com, righi.andrea@gmail.com, guijianfeng@cn.fujitsu.com, balbir@linux.vnet.ibm.com, ctalbott@google.com, nauman@google.com, mrubin@google.com Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3427 Lines: 88 On Thu, Mar 10, 2011 at 6:47 PM, Vivek Goyal wrote: > On Wed, Mar 09, 2011 at 10:04:11AM -0800, Justin TerAvest wrote: >> On Tue, Mar 8, 2011 at 2:50 PM, Vivek Goyal wrote: >> > On Tue, Mar 08, 2011 at 05:43:25PM -0500, Vivek Goyal wrote: >> >> On Tue, Mar 08, 2011 at 01:20:50PM -0800, Justin TerAvest wrote: >> >> > This patchset adds tracking to the page_cgroup structure for which cgroup has >> >> > dirtied a page, and uses that information to provide isolation between >> >> > cgroups performing writeback. >> >> > >> >> >> >> Justin, >> >> >> >> So if somebody is trying to isolate a workload which does bunch of READS >> >> and lots of buffered WRITES, this patchset should help in the sense that >> >> all the heavy WRITES can be put into a separate cgroup of low weight? >> >> >> >> Other application which are primarily doing READS, direct WRITES or little >> >> bit of buffered WRITES should still get good latencies if heavy writer >> >> is isolated in a separate group? >> >> >> >> If yes, then this piece standalone can make sense. And once the other >> >> piece/patches of memory cgroup dirty ratio and cgroup aware buffered >> >> writeout come in, then one will be able to differentiate buffered writes >> >> of different groups. >> > >> > Thinking more about it, currently anyway SYNC preempts the ASYNC. So the >> > question would be will it help me enable get better isolation latencies >> > of READS agains buffered WRITES? >> >> Ah! Sorry, I left out a patch that disables cross-group preemption. >> I'll add that to the patchset and email out v2 soon. > > Well, what I was referring to that even in current code sync preempts > all async in CFQ. So it looks like this patchset will not help get > better latencies in presence of WRITES? Hi Vivek, I should have been more clear. I forgot to include a patch that changes the behavior of that preemption. I haven't mailed out v2 yet because I was also writing a change to put the css_id in pc->flags instead of its own field. The preemption change would look like: Previously, a sync queue in can preempt an async queue in another cgroup. This changes that behavior to disallow such preemption. diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index ab7a216..0494c0c 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3390,6 +3390,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue if (!cfqq) return false; + if (new_cfqq->cfqg != cfqq->cfqg) + return false; + if (cfq_class_idle(new_cfqq)) return false; @@ -3409,9 +3412,6 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) return true; - if (new_cfqq->cfqg != cfqq->cfqg) - return false; I will include the test results that show that isolation is also improved between a reader and a buffered writer. Thanks, Justin > > The only place it can help is that one is looking for service differentation > between two or more buffered write streams. For that we need to fix > upper layers first. > > Vivek > -- 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/