From owner-freebsd-questions@FreeBSD.ORG Thu Nov 23 02:13:52 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 3329A16A522 for ; Thu, 23 Nov 2006 02:13:51 +0000 (UTC) (envelope-from freebsd@sopwith.solgatos.com) Received: from schitzo.solgatos.com (pool-71-117-237-189.ptldor.fios.verizon.net [71.117.237.189]) by mx1.FreeBSD.org (Postfix) with ESMTP id BE29743D5E for ; Thu, 23 Nov 2006 02:13:13 +0000 (GMT) (envelope-from freebsd@sopwith.solgatos.com) Received: from schitzo.solgatos.com (localhost.home.localnet [127.0.0.1]) by schitzo.solgatos.com (8.13.8/8.13.6) with ESMTP id kAN2Dj4d011590 for ; Wed, 22 Nov 2006 18:13:45 -0800 Received: from sopwith.solgatos.com (uucp@localhost) by schitzo.solgatos.com (8.13.8/8.13.4/Submit) with UUCP id kAN2DjCt011587 for freebsd-questions@freebsd.org; Wed, 22 Nov 2006 18:13:45 -0800 Received: from localhost by sopwith.solgatos.com (8.8.8/6.24) id CAA03777; Thu, 23 Nov 2006 02:12:06 GMT Message-Id: <200611230212.CAA03777@sopwith.solgatos.com> To: freebsd-questions@freebsd.org In-reply-to: Your message of "Wed, 22 Nov 2006 20:17:51 EST." <20061123011751.GA45406@xor.obsecurity.org> Date: Wed, 22 Nov 2006 18:12:06 +0000 From: Dieter Subject: Re: processes not getting fair share of available disk I/O (was: Re: TCP parameters and interpreting tcpdump output ) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Nov 2006 02:13:52 -0000 In message <20061123011751.GA45406@xor.obsecurity.org>, Kris Kennaway writes: > > --mP3DRpeJDSE+ciuQ > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > Content-Transfer-Encoding: quoted-printable > > On Wed, Nov 22, 2006 at 11:02:54AM +0000, Dieter wrote: > > In message <20061122165238.GA37819@xor.obsecurity.org>, Kris Kennaway wri= > tes: > >=20 > > > > > I'm surprised that you're seeing that much of a "hang". Even if th= > e di=3D > > > sks > > > > > are busy, the system should slow down all disk processes equally, s= > o no > > > > > one process "blocks", but they're all a little slower. > > > >=3D20 > > > > I collected a bit of data: > > > >=3D20 > > > > While copying a large file from disk1 to disk2, > > > >=3D20 > > > > time ls on a small directory on disk3 (not cached in memory) > > > >=3D20 > > > > real 0m0.032s > > > > user 0m0.000s > > > > sys 0m0.003s > > > >=3D20 > > > > time ls on a small directory on disk2 > > > >=3D20 > > > > real 4m51.911s > > > > user 0m0.000s > > > > sys 0m0.002s > > > >=3D20 > > > > I expect access to a busy disk to take longer, but 5 minutes is > > > > a bit much. And that's the root directory of the filesystem, > > > > it didn't have to follow a long chain of directories to get there. > > > >=3D20 > > > > Sometimes I see long delays when accessing disk3, but it is > > > > behaving at the moment. > > >=20 > > > ls still has to acquire a number of locks in order to be sure that the > > > contents of the directory aren't changing. If there are lots of other > > > processes all competing for these locks, it will be slow. It looks > > > like that's the case on your system, although details of your workload > > > have been trimmed from your email. > >=20 > > In telnet window 1: > >=20 > > cd /disk1/ > > cp -ip very_big_file /disk2/bar/ (the workload) > >=20 > > In telnet window 2: > >=20 > > time ls /disk3/foo1/ (make sure time and ls are cached in memory) > > time ls /disk3/foo2/ (see timing numbers above) > > time ls /disk2/ (see timing numbers above) > >=20 > > The /disk2/ directory is small, only contains 3 directories and .snap > >=20 > > Would the cp into /disk2/bar/ lock the /disk2/ directory? > > It shouldn't do. > > What scheduler are you using? kern.sched.name: 4BSD kern.sched.quantum: 100000 kern.sched.preemption: 1