From owner-freebsd-hackers@FreeBSD.ORG Tue Apr 17 19:30:15 2012 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id AB1DD106564A for ; Tue, 17 Apr 2012 19:30:15 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.freebsd.org (Postfix) with ESMTP id 791C08FC15 for ; Tue, 17 Apr 2012 19:30:15 +0000 (UTC) Received: by pbcwz17 with SMTP id wz17so8495688pbc.13 for ; Tue, 17 Apr 2012 12:30:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=lvBWUk6qbY9MNmHPHHE4qmG28hM1xlkuJBWOF6XLBgU=; b=TJHNGbgn9JVH/4Hnmi/Tt4fnzpr9NwvBQN4a3OurzTjmis67FHF3DYtANZKoEmk6F2 opqvHsaAiFDcQ2OsR/dK7cXR59atY0Ha4YUynUcxaKC6wpru94vn6b3EWfz0DlK0xdc3 qgXPujbFpTGXDLUXD0DED8oKMKqYp20BdNUXnyRZdG84PxlYFQuVWtrBlmm55iBzWNUq ylF4gQ4NlQl6Kod4d49GXtomBS/xyFQs9HUstn8gPsK9OtroALoxwQrPswCTODgOey2Z ajS7cMp/25otQaE19AnC6iJK3FghDCw94Uw4rZw9/CoavITiVkIC0WhM56JvrIybr/mt OXlA== MIME-Version: 1.0 Received: by 10.68.225.132 with SMTP id rk4mr37431473pbc.157.1334691015211; Tue, 17 Apr 2012 12:30:15 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.142.101.9 with HTTP; Tue, 17 Apr 2012 12:30:15 -0700 (PDT) In-Reply-To: <20120417211558.4793b705@ernst.jennejohn.org> References: <20120403193124.46ad9de9@ernst.jennejohn.org> <20120411192153.5672b62c@ernst.jennejohn.org> <20120417211558.4793b705@ernst.jennejohn.org> Date: Tue, 17 Apr 2012 12:30:15 -0700 X-Google-Sender-Auth: alSrn_PnJ8z4amImwK3AFFLX1OY Message-ID: From: Adrian Chadd To: gljennjohn@googlemail.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-hackers , Jerry Toung Subject: Re: CAM disk I/O starvation X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Apr 2012 19:30:15 -0000 On 17 April 2012 12:15, Gary Jennejohn wrote: > Yes, I agree completely. =A0My first thought was that disk I/O > scheduling had somehow been pessimized. =A0But then I thought - > wait a minute, I have disk caches enabled and command queuing is > enabled for all of them, so that shouldn't really have any > noticeable impact. =A0So I was at a loss to explain why disk performance > had suddenly gotten so bad. That's assuming there are no bugs anywhere. :) > I'd be willing to spend some time on diagnosing it, but I have to come > up with a scenario which would reliably reproduce the problem. =A0AFAICR > it generally happened when I was running csup/svn because my CVS > repositoy is on one disk and /usr/{ports,src} are on a different one. > > I still have the old problem kernel around, but it's probably not > instrumented for any meaningful diagnoses. Well do you know which version of which tree you used to build that? If it's head, you could "just" keep an earlier source tree around to build a kernel from. Adrian