From owner-freebsd-current@FreeBSD.ORG Sun Sep 18 02:20:41 2005 Return-Path: X-Original-To: current@freebsd.org Delivered-To: freebsd-current@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3CDB116A41F for ; Sun, 18 Sep 2005 02:20:41 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8CC9743D45 for ; Sun, 18 Sep 2005 02:20:40 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from [192.168.254.11] (junior.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.13.4/8.13.4) with ESMTP id j8I2KVrv016045; Sat, 17 Sep 2005 20:20:31 -0600 (MDT) (envelope-from scottl@samsco.org) Message-ID: <432CCEF5.2050608@samsco.org> Date: Sat, 17 Sep 2005 20:20:37 -0600 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.8) Gecko/20050615 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andrew Gallatin References: <20050914194612.15692485.lehmann@ans-netz.de> <20050914222013.178dc4dc.lehmann@ans-netz.de> <84dead72050914135239514c49@mail.gmail.com> <20050915000053.448f251b.lehmann@ans-netz.de> <84dead7205091500152a7c25d1@mail.gmail.com> <20050915172005.072f4bdf.lehmann@ans-netz.de> <20050915181238.54b16b4b.lehmann@ans-netz.de> <84dead720509160921732e7f96@mail.gmail.com> <20050916184911.38e2739a.lehmann@ans-netz.de> <20050916225219.73b53cd0.lehmann@ans-netz.de> <84dead7205091619435c12b528@mail.gmail.com> <20050917102846.7bf26a56.lehmann@ans-netz.de> <17196.35762.395155.325627@grasshopper.cs.duke.edu> In-Reply-To: <17196.35762.395155.325627@grasshopper.cs.duke.edu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.8 required=3.8 tests=ALL_TRUSTED autolearn=failed version=3.0.2 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on pooker.samsco.org Cc: current@freebsd.org Subject: Re: low(er) disk performance with sched_4bsd then with sched_ule X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 18 Sep 2005 02:20:41 -0000 Andrew Gallatin wrote: > Oliver Lehmann writes: > > Joseph Koshy wrote: > > > > > ol> Wow, that update to BETA4 did the trick! While running > > > ol> SCHED_4BSD: > > > > > > Fantastic! What is the profile like with the new 4BSD kernel? > > > > http://pofo.de/tmp/gprof.4bsd.3 > > I don't know the disk codepath very well, but the samples look a > little suspect. We're copying a lot of data into and out of the > kernel, so I would expect the majority of non disk wait time would be > spent simply copying out the zero-filled pages, and copying them back > in (AFAIK, dd uses read/write). Where is the time spent in read, > write, uiomove, bcopy? > > What about ionode allocations, etc? And why do things like > g_bsd_modify and g_bsd_ioctl rank so high? Aren't those only used > when dealing with disklabels? > > BTW, I *love* that we've got access to the hw counters, and an easy > way to do low-overhead profiling of the kernel. > > Drew > I don't know if it's the case here or not, but GCC now does very aggressive function inlining, so much so that it's nearly impossible to look at a backtrace and figure out what the actual call path was. Compiling with -O instead of the -O2 default turns off this 'feature' (and I use that term quite liberally), so it might be useful to recompile there kernel with 'CFLAGS= -O' in /etc/make.conf and see if it changes the profiling numbers at all. Also, I think that there was some talk last year about things like preemption and fast interrupts screwing up certain kinds of profiling. I don't recall if there was a solution to this, though. Scott