From owner-freebsd-smp@FreeBSD.ORG Fri May 6 19:05:56 2005 Return-Path: Delivered-To: freebsd-smp@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0D93C16A4D4 for ; Fri, 6 May 2005 19:05:56 +0000 (GMT) Received: from mail.rfnj.org (ns1.rfnj.org [66.180.172.156]) by mx1.FreeBSD.org (Postfix) with ESMTP id A08AD43D1D for ; Fri, 6 May 2005 19:05:55 +0000 (GMT) (envelope-from asym@rfnj.org) Received: from megalomaniac.rfnj.org (ool-45736df1.dyn.optonline.net [69.115.109.241]) by mail.rfnj.org (Postfix) with ESMTP id ED7562B6; Fri, 6 May 2005 15:05:55 -0400 (EDT) Message-Id: <6.2.1.2.2.20050506150138.036b83c0@mail.rfnj.org> X-Mailer: QUALCOMM Windows Eudora Version 6.2.1.2 Date: Fri, 06 May 2005 15:11:39 -0400 To: Kris Kennaway From: Allen In-Reply-To: <20050506184852.GA62656@xor.obsecurity.org> References: <20050506183529.GA46411@xor.obsecurity.org> <20050506184852.GA62656@xor.obsecurity.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed cc: smp@FreeBSD.org Subject: Re: Benchmarking mpsafevfs with parallel tarball extraction X-BeenThere: freebsd-smp@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: FreeBSD SMP implementation group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 May 2005 19:05:56 -0000 At 14:48 5/6/2005, Kris Kennaway wrote: >On Fri, May 06, 2005 at 11:35:29AM -0700, Kris Kennaway wrote: > > > I might be bumping into the bandwidth of md here - when I ran less > > rigorous tests with lower concurrency of extractions I seemed to be > > getting marginally better performance (about an effective concurrency > > of 2.2 for both 3 and 10 simultaneous extractions - so at least it > > doesn't seem to degrade badly). Or this might be reflecting VFS lock > > contention (which there is certainly a lot of, according to mutex > > profiling traces). > >I suspect that I am hitting the md bandwidth: > ># dd if=/dev/zero of=/dev/md0 bs=1024k count=500 >500+0 records in >500+0 records out >524288000 bytes transferred in 9.501760 secs (55177988 bytes/sec) > >which is a lot worse than I expected (even for a 400MHz CPU). That looks pretty goofy. Even PC66 SDRAM should be able to push ~250MB/s on a very slow processor. Does the md code for raw access really load this much work onto the CPU?? >For some reason I get better performance writing to a filesystem >mounted on this md: Part of me wants to think that maybe this is due to some fashion of metadata caching, in the manner of softupdates. Possible?