From: Jeff King <peff@peff.net>
To: Nicolas Pitre <nico@cam.org>
Cc: Jon Smirl <jonsmirl@gmail.com>,
Daniel Berlin <dberlin@dberlin.org>,
Harvey Harrison <harvey.harrison@gmail.com>,
David Miller <davem@davemloft.net>,
ismail@pardus.org.tr, gcc@gcc.gnu.org, git@vger.kernel.org
Subject: Re: Git and GCC
Date: Fri, 7 Dec 2007 01:50:47 -0500 [thread overview]
Message-ID: <20071207065047.GB13101@coredump.intra.peff.net> (raw)
In-Reply-To: <alpine.LFD.0.99999.0712061246120.555@xanadu.home>
On Thu, Dec 06, 2007 at 01:02:58PM -0500, Nicolas Pitre wrote:
> > What is really disappointing is that we saved
> > only about 20% of the time. I didn't sit around watching the stages, but
> > my guess is that we spent a long time in the single threaded "writing
> > objects" stage with a thrashing delta cache.
>
> Maybe you should run the non threaded repack on the same machine to have
> a good comparison.
Sorry, I should have been more clear. By "saved" I meant "we needed N
minutes of CPU time, but took only M minutes of real time to use it."
IOW, if we assume that the threading had zero overhead and that we were
completely CPU bound, then the task would have taken N minutes of real
time. And obviously those assumptions aren't true, but I was attempting
to say "it would have been at most N minutes of real time to do it
single-threaded."
> And if you have only 2 CPUs, you will have better performances with
> pack.threads = 2, otherwise there'll be wasteful task switching going
> on.
Yes, but balanced by one thread running out of data way earlier than the
other, and completing the task with only one CPU. I am doing a 4-thread
test on a quad-CPU right now, and I will also try it with threads=1 and
threads=6 for comparison.
> And of course, if the delta cache is being trashed, that might be due to
> the way the existing pack was previously packed. Hence the current pack
> might impact object _access_ when repacking them. So for a really
> really fair performance comparison, you'd have to preserve the original
> pack and swap it back before each repack attempt.
I am working each time from the pack generated by fetching from
git://git.infradead.org/gcc.git.
-Peff
next prev parent reply other threads:[~2007-12-07 6:51 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4aca3dc20712051108s216d3331t8061ef45b9aa324a@mail.gmail.com>
2007-12-06 2:28 ` Git and GCC David Miller
2007-12-06 2:41 ` Daniel Berlin
2007-12-06 2:52 ` David Miller
2007-12-06 3:47 ` Daniel Berlin
2007-12-06 4:20 ` David Miller
2007-12-06 4:28 ` Harvey Harrison
2007-12-06 4:32 ` Daniel Berlin
2007-12-06 4:48 ` David Miller
2007-12-06 5:11 ` Daniel Berlin
2007-12-06 5:15 ` Harvey Harrison
2007-12-06 5:17 ` Daniel Berlin
2007-12-06 6:47 ` Jon Smirl
2007-12-06 7:15 ` Jeff King
2007-12-06 14:18 ` Nicolas Pitre
2007-12-06 17:39 ` Jeff King
2007-12-06 18:02 ` Nicolas Pitre
2007-12-07 6:50 ` Jeff King [this message]
2007-12-07 7:27 ` Jeff King
2007-12-06 18:35 ` Linus Torvalds
2007-12-06 18:55 ` Jon Smirl
2007-12-06 19:08 ` Nicolas Pitre
2007-12-06 21:39 ` Jon Smirl
2007-12-06 22:08 ` Nicolas Pitre
2007-12-06 22:11 ` Jon Smirl
2007-12-06 22:22 ` Jon Smirl
2007-12-06 22:30 ` Nicolas Pitre
2007-12-06 22:44 ` Jon Smirl
2007-12-07 7:31 ` Jeff King
2007-12-08 0:47 ` Harvey Harrison
2007-12-10 9:54 ` Gabriel Paubert
2007-12-10 15:35 ` Nicolas Pitre
2007-12-07 3:31 ` David Miller
2007-12-07 6:38 ` Jeff King
2007-12-07 7:10 ` Jon Smirl
2007-12-07 12:53 ` David Miller
2007-12-07 17:23 ` Linus Torvalds
2007-12-07 20:26 ` Giovanni Bajo
2007-12-07 22:14 ` Jakub Narebski
2007-12-07 23:04 ` Luke Lu
2007-12-07 23:14 ` Giovanni Bajo
2007-12-07 23:33 ` Daniel Berlin
2007-12-08 12:00 ` Johannes Schindelin
2007-12-08 1:55 ` David Miller
2007-12-10 9:57 ` David Miller
2007-12-06 6:09 ` Linus Torvalds
2007-12-06 7:49 ` Harvey Harrison
2007-12-06 8:11 ` David Brown
2007-12-06 14:01 ` Nicolas Pitre
2007-12-06 12:03 ` [PATCH] gc --aggressive: make it really aggressive Johannes Schindelin
2007-12-06 13:42 ` Theodore Tso
2007-12-06 14:15 ` Nicolas Pitre
2007-12-06 14:22 ` Pierre Habouzit
2007-12-06 15:55 ` Johannes Schindelin
2007-12-06 17:05 ` David Kastrup
2007-12-06 15:30 ` Harvey Harrison
2007-12-06 15:56 ` Johannes Schindelin
2007-12-06 16:19 ` Linus Torvalds
2009-03-18 16:01 ` Johannes Schindelin
2009-03-18 16:27 ` Teemu Likonen
2009-03-18 18:02 ` Nicolas Pitre
2007-12-06 18:04 ` Git and GCC Daniel Berlin
2007-12-06 18:29 ` Linus Torvalds
2007-12-07 2:42 ` Harvey Harrison
2007-12-07 3:01 ` Linus Torvalds
2007-12-07 4:06 ` Jon Smirl
2007-12-07 4:21 ` Nicolas Pitre
2007-12-07 5:21 ` Linus Torvalds
2007-12-07 7:08 ` Jon Smirl
2007-12-07 19:36 ` Nicolas Pitre
2007-12-06 18:24 ` NightStrike
2007-12-06 18:45 ` Linus Torvalds
2007-12-07 5:36 ` NightStrike
2007-12-06 19:12 ` Jon Loeliger
2007-12-06 19:39 ` Linus Torvalds
2007-12-07 0:29 ` Jakub Narebski
2007-12-06 20:04 ` Junio C Hamano
2007-12-06 21:02 ` Junio C Hamano
2007-12-06 22:26 ` David Kastrup
2007-12-06 22:38 ` [OT] " Randy Dunlap
2007-12-06 4:25 ` Harvey Harrison
2007-12-06 4:54 ` Linus Torvalds
2007-12-06 5:04 ` Harvey Harrison
2007-12-06 11:57 ` Johannes Schindelin
2007-12-06 12:04 ` Ismail Dönmez
[not found] ` <2007-12-05-21-23-14+trackit+sam@rfc1149.net>
[not found] ` <1196891451.10408.54.camel@brick>
[not found] ` <jeeje0ogvk.fsf@sykes.suse.de>
[not found] ` <1196897840.10408.57.camel@brick>
[not found] ` <38a0d8450712130640p1b5d74d6nfa124ad0b0110d64@mail.gmail.com>
[not found] ` <1197572755.898.15.camel@brick>
2007-12-17 22:15 ` "Argument list too long" in git remote update (Was: Git and GCC) Geert Bosch
2007-12-17 22:59 ` Johannes Schindelin
2007-12-17 23:01 ` Linus Torvalds
2007-12-18 1:34 ` Derek Fawcus
2007-12-18 1:52 ` Shawn O. Pearce
2007-12-08 2:21 Git and GCC J.C. Pizarro
2007-12-08 12:24 ` Johannes Schindelin
2007-12-08 19:53 ` Joe Buck
2007-12-08 20:28 ` Marco Costalba
2007-12-09 1:51 ` Daniel Berlin
2007-12-15 0:18 ` Nix
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