Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757870AbZKDTMv (ORCPT ); Wed, 4 Nov 2009 14:12:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757850AbZKDTMu (ORCPT ); Wed, 4 Nov 2009 14:12:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48225 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757812AbZKDTMs (ORCPT ); Wed, 4 Nov 2009 14:12:48 -0500 Date: Wed, 4 Nov 2009 14:12:32 -0500 From: Vivek Goyal To: Jeff Moyer 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 11/20] blkio: Some CFQ debugging Aid Message-ID: <20091104191232.GI2870@redhat.com> References: <1257291837-6246-1-git-send-email-vgoyal@redhat.com> <1257291837-6246-12-git-send-email-vgoyal@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2080 Lines: 66 On Wed, Nov 04, 2009 at 01:52:51PM -0500, Jeff Moyer wrote: > Vivek Goyal writes: > > > o Some CFQ debugging Aid. > > Some CFQ debugging aids. Sorry, I couldn't help myself. > It thought this was all about IO controller and not english grammar. :-) Will fix it. > > +config DEBUG_BLK_CGROUP > > + bool > > + depends on BLK_CGROUP > > + default n > > + ---help--- > > + Enable some debugging help. Currently it stores the cgroup path > > + in the blk group which can be used by cfq for tracing various > > + group related activity. > > + > > endif # BLOCK > > > > > +config DEBUG_CFQ_IOSCHED > > + bool "Debug CFQ Scheduling" > > + depends on CFQ_GROUP_IOSCHED > > + select DEBUG_BLK_CGROUP > > This seems wrong. DEBUG_CFQ_IOSCHED sounds like it enables debugging of > CFQ. In your implementation, though, it only enables this in tandem > with the blkio cgroup infrastructure. Please decouple these things. > What's wrong with this? We are emitting more debugging information for CFQ like cgroup name and paths in blktrace output. That's a different thing that internally that information is also dependent debugging being enabled in blk io controller. Important thing here is that blk io controller and its debugging option is automatically selected depending on what user wants from end policies. So I really can't see that what's wrong if CFQ debugging option internally selects some other config option also. > > +#ifdef CONFIG_DEBUG_BLK_CGROUP > > + /* Store cgroup path */ > > + char path[128]; > > +#endif > > Where does 128 come from? What's wrong with PATH_MAX? CFS influence (kernel/sched_debug.c) Actually PATH_MAX will be 4096 bytes. Too long to display in blktrace output? I have not check what's the blktrace limit but we don't want too long a lines in output. Thanks 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/