From owner-freebsd-stable@FreeBSD.ORG Sun Mar 6 01:49:48 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 3D0A71065670 for ; Sun, 6 Mar 2011 01:49:48 +0000 (UTC) (envelope-from illoai@gmail.com) Received: from mail-fx0-f54.google.com (mail-fx0-f54.google.com [209.85.161.54]) by mx1.freebsd.org (Postfix) with ESMTP id C2E6A8FC08 for ; Sun, 6 Mar 2011 01:49:47 +0000 (UTC) Received: by fxm19 with SMTP id 19so3636494fxm.13 for ; Sat, 05 Mar 2011 17:49:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=rzs2oaZk7fDFpL6dc+gXrxvqna3a6OtLK8i8m/VIkZs=; b=FVoZ3wZpep3PpCv3LnXSm0iQird73F4rLLtU5oKfTB6c1IHNxAPWFWQ7cnTrHgamlk Ma4EYEzF8rztLNa0yuM2VVAcwDST494VRt8qXuBwuJEoehe3OAX2EmHNe5jxDPMJQEwV OsLPIh2NjJihNluTx4KiEDZKlk6E0GZ3aXj44= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=m4axZGyUQzgWHpHyj29le9GmiP/lNYRfVh2jptUfoAS7UGhRw3N4QGDe+FA7j0Kgvq /Q+qhhWC8x7d1YDvipY5Gtyw8c29ARTQxDjhMLfanJs23FGDm0kxdqFaz7XdAt4VPIYD qJw8Wn1JixzFP3ZRcWZWHbHGzqBwDnBMtOYTg= MIME-Version: 1.0 Received: by 10.223.151.9 with SMTP id a9mr756739faw.40.1299376186765; Sat, 05 Mar 2011 17:49:46 -0800 (PST) Received: by 10.223.96.203 with HTTP; Sat, 5 Mar 2011 17:49:46 -0800 (PST) In-Reply-To: <20110306014355.GA36763@icarus.home.lan> References: <20110305234514.GA34594@icarus.home.lan> <20110306010140.GA90699@lava.net> <20110306014355.GA36763@icarus.home.lan> Date: Sat, 5 Mar 2011 20:49:46 -0500 Message-ID: From: "illoai@gmail.com" To: Jeremy Chadwick Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-stable@freebsd.org Subject: Re: Strange performance issue with grep -r -i as non-root user 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: Sun, 06 Mar 2011 01:49:48 -0000 On 5 March 2011 20:43, Jeremy Chadwick wrote: > On Sat, Mar 05, 2011 at 03:01:40PM -1000, Clifton Royston wrote: >> On Sat, Mar 05, 2011 at 03:45:14PM -0800, Jeremy Chadwick wrote: >> > This is a strange one, and the more I started debugging it (starting >> > with truss, comparing fast vs. slow results, where all that appears >> > different is read() operations are taking a lot longer -- I haven't ha= d >> > time to check with ktrace yet), the more strange it got: that's when I >> > found out the behaviour changes depending on if you're a user or root. >> > >> > Easy to reproduce: >> > >> > - grep -r string /usr/src, as non-root, is fast >> > - grep -r -i string /usr/src, as non-root, is 8x slower than without -= i >> >> =A0 From your results below, I think you mean *80* x slower! > > Oops; yes, typo on my part. =A0I was never any good at math either! =A0;-= ) > >> > - grep -r string /usr/src, as root, is fast >> > - grep -r -i string /usr/src, as root, is fast >> >> =A0 I can not reproduce this on 7.3-RELEASE-p4; I get consistent results >> between root and non-root, with -i being only marginally slower (about >> 15%) for each; results below. > > Your results look more or less like what I see on the 4th system (the > 7.0-STABLE one). =A0I believe the speed difference there (and on your > system) is justified, as I would imagine strcasecmp() a tiny bit slower > than strcmp(). =A0But an 80x slowdown is completely unacceptable, > especially given the conditions. > > My first thought was "compiler optimisation bug?", which I suppose could > still be the case, but I don't know how root vs. non-root would change > that behaviour, not to mention only when -i was specified. > > Using 'truss -d' it looks like the slowdown is happening on read(2), > which makes me very concerned, as it could indicate something odd going > on with CAM? =A0Sadly I cannot (for many reasons) get rid of ahci.ko on > any of those 3 systems, so I can't compare stock ata(4) to ahci.ko > easily on the same system. > On my 8.2-RELEASE system using ahci (built into the custom kernel) I don't notice your observed slowdown, so unless ahci is radically different on -STABLE I doubt it's the cause. --=20 --