Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757926AbZKDTai (ORCPT ); Wed, 4 Nov 2009 14:30:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756031AbZKDTah (ORCPT ); Wed, 4 Nov 2009 14:30:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48920 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755988AbZKDTah (ORCPT ); Wed, 4 Nov 2009 14:30:37 -0500 From: Jeff Moyer To: Vivek Goyal Cc: linux-kernel@vger.kernel.org, jens.axboe@oracle.com, nauman@google.com, dpshah@google.com, lizf@cn.fujitsu.com, ryov@valinux.co.jp, fernando@oss.ntt.co.jp, s-uchida@ap.jp.nec.com, taka@valinux.co.jp, guijianfeng@cn.fujitsu.com, balbir@linux.vnet.ibm.com, righi.andrea@gmail.com, m-ikeda@ds.jp.nec.com, akpm@linux-foundation.org, riel@redhat.com, kamezawa.hiroyu@jp.fujitsu.com Subject: Re: [PATCH 15/20] blkio: Take care of preemptions across groups References: <1257291837-6246-1-git-send-email-vgoyal@redhat.com> <1257291837-6246-16-git-send-email-vgoyal@redhat.com> <20091104192725.GM2870@redhat.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 04 Nov 2009 14:30:13 -0500 In-Reply-To: <20091104192725.GM2870@redhat.com> (Vivek Goyal's message of "Wed, 4 Nov 2009 14:27:25 -0500") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1221 Lines: 34 Vivek Goyal writes: > It will not as we traverse up the hierarchy and look for the ioprio class > of the group entity. > > So if you got following configuration where G1 and G2 are two groups. G1 > is prio class RT and G2 is prio class BE, then any queue in G1 will > preempt any queue in G2 as at highest level, G1 and G2 are different class > altogether. > > root > / \ > G1 G2 > > Normal cfqq preemption checks will not catch this. So if G2 has some BE > cfqq running, and some BE queue gets backlogged in G1, this new queue wil > not preempt the queue in G2 and it should have. > > That's why preemption checks at group level. > > Secondly if G1 and G2 are of ioprioclass BE and all the jobs in G1 are of > RT nature, they will not preempt the queues in G2, hence providing > isolation. Thanks for the explanation, Vivek. I somehow missed that we were checking the class of the group entity and not the cfqq's entity. Cheers, Jeff -- 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/