From owner-freebsd-current@FreeBSD.ORG Sat Feb 14 15:44:50 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C8599106564A; Sat, 14 Feb 2009 15:44:50 +0000 (UTC) (envelope-from ivoras@gmail.com) Received: from mail-fx0-f11.google.com (mail-fx0-f11.google.com [209.85.220.11]) by mx1.freebsd.org (Postfix) with ESMTP id F21C78FC0A; Sat, 14 Feb 2009 15:44:49 +0000 (UTC) (envelope-from ivoras@gmail.com) Received: by fxm4 with SMTP id 4so483678fxm.19 for ; Sat, 14 Feb 2009 07:44:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to:cc :content-type:content-transfer-encoding; bh=MzNZtZqvxnFQ+iZMGbu2ODQMVZdEF0YjKl/UunRAN0w=; b=fH9Z/JwW2FMYlJsEjWvAU9ya5ZqehmJD36g2t14AIMYsqzPjxXBJP++xImZmqQbW/9 yvCqsMlToQ98L8DT2V6HJR2W1wP+9D79mhXFdhTtc29SFbvu56WPST9z2AwnzVd4VjJP 2yFkjos2TP2LFBQyMAAfXnAYvMI7CTl4LJaP8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=L9KN4Xufif41LhK/h9yQxNq0pGBp45SZ3d5c15O8SnLC12sbh0DPayVMbWob5CmcHN gufAGccetvIjsCG+dHkYrt0tpfEsOYogLCPK3b6EfrEuynPnnINhPQhq6vE1oDw6eYze Ic470e8cs9XN/z3LRyZ0YTFSEi2u5bM7As5KE= MIME-Version: 1.0 Sender: ivoras@gmail.com Received: by 10.181.205.3 with SMTP id h3mr1172052bkq.91.1234626287238; Sat, 14 Feb 2009 07:44:47 -0800 (PST) In-Reply-To: <4996D635.3000802@samsco.org> References: <499551B9.7050805@samsco.org> <4995DFE5.1020205@samsco.org> <9bbcef730902131421r53efa13dq371658888747f387@mail.gmail.com> <4996D635.3000802@samsco.org> Date: Sat, 14 Feb 2009 16:44:47 +0100 X-Google-Sender-Auth: 11fbe127f30ffea4 Message-ID: <9bbcef730902140744i14c2a9e6i211a549eada7b057@mail.gmail.com> From: Ivan Voras To: Scott Long Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: freebsd-current@freebsd.org, freebsd-stable@freebsd.org Subject: Re: HEADS UP: Major CAM performance regression 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: Sat, 14 Feb 2009 15:44:51 -0000 2009/2/14 Scott Long : >> I'll try your suggestion if you have one. > > I don't have a magic universal testing suite in my back pocket, sorry. > You need to look at your expected workload and develop tests to simulate > it. When I do testing during driver development, I try a lot of > different parallel, sequential, large i/o, and small i/o combinations. Of course you're right about testing for specific workloads - I just thought you needed data points "from the field" if the patch is helping or not. >> (except if it's about bonnie++ primarily measuring sequential >> read/write - if a system can't do sequential IO well, it probably >> won't do random IO well) > > This is completely false. Disks can't do sequential i/o very well due > to the physical limits of long seek times, but those seek times can be I don't follow this - where are the long seek times in sequential IO? > greatly amortized, even in a random workload, with tagged queueing and > parallel dispatch from the OS. Bonnie simply cannot exercise this very > well. > > Bonnie tests system latency for discrete I/O's. That is all it tests. Doesn't tagged queuing serve, among other things, to decrease overall latency for IOs? Since AFAIK UFS queues multiple IO requests in both directions (read-ahead and write-behind), shouldn't the benefits of the patch - liberating the tags - be visible even with sequential IO? I have the systems on which I tested for a few more days, if you need the data I can run some other tests (randomio?).