From owner-freebsd-stable@FreeBSD.ORG Thu Dec 15 16:26:06 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9E9FD10657A5; Thu, 15 Dec 2011 16:26:06 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-qy0-f182.google.com (mail-qy0-f182.google.com [209.85.216.182]) by mx1.freebsd.org (Postfix) with ESMTP id EC5318FC15; Thu, 15 Dec 2011 16:26:05 +0000 (UTC) Received: by qcse13 with SMTP id e13so1932910qcs.13 for ; Thu, 15 Dec 2011 08:26:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; 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; bh=qn2SX6Icz3xoH1/LZzTteZ2wkKvJHUss5vkQbFTGw88=; b=fgLJMqgdAh/wrr7kqbGLvkkEYs/vl6PwMjS1eUHzw+Eqwmeba6B1V4Bqvz3ZzFiXbA uBH1/bfrSGDC5L+hehANmNWfGcPqfSl4swHJjcmGBNxNONeZcJEIg1zVYOm3Hw0io+gZ U+OFVnzlUpdDILUKmKplz5cJrlJthd9/6/aY8= MIME-Version: 1.0 Received: by 10.180.74.211 with SMTP id w19mr6552377wiv.7.1323966364698; Thu, 15 Dec 2011 08:26:04 -0800 (PST) Sender: asmrookie@gmail.com Received: by 10.216.171.8 with HTTP; Thu, 15 Dec 2011 08:26:04 -0800 (PST) In-Reply-To: <4EE8D607.1000504@sentex.net> References: <4EE1EAFE.3070408@m5p.com> <4EE22421.9060707@gmail.com> <4EE6060D.5060201@mail.zedat.fu-berlin.de> <4EE69C5A.3090005@FreeBSD.org> <20111213104048.40f3e3de@nonamehost.> <20111213230441.GB42285@stack.nl> <4ee7e2d3.0a3c640a.4617.4a33SMTPIN_ADDED@mx.google.com> <4EE8D607.1000504@sentex.net> Date: Thu, 15 Dec 2011 17:26:04 +0100 X-Google-Sender-Auth: RQHg7a4l9VdsnVFWmvoxYxji0G8 Message-ID: From: Attilio Rao To: Mike Tancsa Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: Ivan Klymenko , mdf@freebsd.org, Doug Barton , freebsd-stable@freebsd.org, Jilles Tjoelker , "O. Hartmann" , Current FreeBSD , freebsd-performance@freebsd.org Subject: Re: SCHED_ULE should not be the default X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Dec 2011 16:26:06 -0000 2011/12/14 Mike Tancsa : > On 12/13/2011 7:01 PM, mdf@freebsd.org wrote: >> >> Has anyone experiencing problems tried to set sysctl kern.sched.steal_th= resh=3D1 ? >> >> I don't remember what our specific problem at $WORK was, perhaps it >> was just interrupt threads not getting serviced fast enough, but we've >> hard-coded this to 1 and removed the code that sets it in >> sched_initticks(). =C2=A0The same effect should be had by setting the >> sysctl after a box is up. > > FWIW, this does impact the performance of pbzip2 on an i7. Using a 1.1G f= ile > > pbzip2 -v -c big > /dev/null > > with burnP6 running in the background, > > sysctl kern.sched.steal_thresh=3D1 > vs > sysctl kern.sched.steal_thresh=3D3 > > > > =C2=A0 =C2=A0N =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Min =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 Max =C2=A0 =C2=A0 =C2=A0 =C2=A0Median =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 Avg =C2=A0 =C2=A0 =C2=A0 =C2=A0Stddev > x =C2=A010 =C2=A0 =C2=A0 38.005022 =C2=A0 =C2=A0 =C2=A038.42238 =C2=A0 = =C2=A0 38.194648 =C2=A0 =C2=A0 38.165052 =C2=A0 =C2=A00.15546188 > + =C2=A0 9 =C2=A0 =C2=A0 38.695417 =C2=A0 =C2=A0 40.595544 =C2=A0 =C2=A0 = 39.392127 =C2=A0 =C2=A0 39.435384 =C2=A0 =C2=A00.59814114 > Difference at 95.0% confidence > =C2=A0 =C2=A0 =C2=A0 =C2=A01.27033 +/- 0.412636 > =C2=A0 =C2=A0 =C2=A0 =C2=A03.32852% +/- 1.08119% > =C2=A0 =C2=A0 =C2=A0 =C2=A0(Student's t, pooled s =3D 0.425627) > > a value of 1 is *slightly* faster. Hi Mike, was that just the same codebase with the switch SCHED_4BSD/SCHED_ULE? Also, the results here should be in the 3% interval for the avg case, which is not yet at the 'alarm level' but could still be an indication. I still suspect I/O plays a big role here, however, thus it could be detemined by other factors. Could you retry the bench checking CPU usage and possible thread migration around for both cases? Thanks, Attilio --=20 Peace can only be achieved by understanding - A. Einstein