Date: Mon, 7 Oct 2013 12:44:05 -0700 From: David Wolfskill <david@catwhisker.org> To: Erik Cederstrand <erik+lists@cederstrand.dk> Cc: performance@freebsd.org Subject: Re: Apparent performance regression 8.3@ -> 8.4@r255966? Message-ID: <20131007194405.GP1611@albert.catwhisker.org> In-Reply-To: <172AF9A7-53F7-42CF-A164-084CFB418EE9@cederstrand.dk> References: <20131007172804.GA7641@albert.catwhisker.org> <172AF9A7-53F7-42CF-A164-084CFB418EE9@cederstrand.dk>
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--Vhqu5qQ3bjg0ZI9i Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Oct 07, 2013 at 09:19:38PM +0200, Erik Cederstrand wrote: > ...=20 > > In examining the CPU utilization graphs, the CPU generally looks > > about 5% busy for the first 15 minutes; this would be bmake determining > > dependency graphs, I expect. >=20 > Is that one process using 100% of one core, or many processes using 5% to= tal? It's closer to the first, but "which core" varies a bit over time. (In one specific instance, core 17, then 13 are at near 100% within that first 15-minute interval.) > > Based on earlier work I did, where I was able to do a similar build in a > > native FreeBSD/i386 (no PAE) enviroment on the same hardware (but when > > it still only had 6GB RAM), and I managed to get the build done in 2:47, > > I believe that getting more work done in parallel in this 2:00 period is > > a key to improving performance: the 2:47 result showed that period to be > > a very busy one for the CPU. >=20 > You need to know where your bottlenecks are during the build. Indeed. :-} > Since you have lots of RAM, you could try to rule out differences in file= system access by placing your jail on an mfs and building your software off= that. That's an experiment that I've been advocating, but 96GB isn't enough. > If that improves build times, then you're IO bound at least some of the t= ime. You should be logging disk access along with CPU and memory during the= build. FWIW, I'm seeing very little CPU time spent in interrupt mode. I'll see if I can find a reasonable way to munge the output of iostat to be usable for the purpose, I suppose; thanks. Peace, david --=20 David H. Wolfskill david@catwhisker.org Taliban: Evil cowards with guns afraid of truth from a 14-year old girl. See http://www.catwhisker.org/~david/publickey.gpg for my public key. --Vhqu5qQ3bjg0ZI9i Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iEYEARECAAYFAlJTDwQACgkQmprOCmdXAD2nfACdGhiKwCZi8hR6WKHcNIFXaTWP CbUAn04e5LE/qsBw+14sNxZLakDGVFNZ =kGWq -----END PGP SIGNATURE----- --Vhqu5qQ3bjg0ZI9i--
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