From: Shawn Pearce <spearce@spearce•org>
To: Nicolas Pitre <nico@cam•org>
Cc: Junio C Hamano <junkio@cox•net>, git@vger•kernel.org
Subject: Re: 1.3.0 creating bigger packs than 1.2.3
Date: Thu, 20 Apr 2006 22:40:12 -0400 [thread overview]
Message-ID: <20060421024012.GA1213@spearce.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0604202213470.2215@localhost.localdomain>
Nicolas Pitre <nico@cam•org> wrote:
> On Thu, 20 Apr 2006, Shawn Pearce wrote:
>
> > Based on Linus' comment I changed your patch to just the following.
> > It still produced the 46M pack file, so the first hunk apears to
> > not have had much of an affect with this data.
> >
> > From a running time perspective it appears as though this patch is
> > making things slightly better, not worse. I ran it a few times
> > for each case always using the 46M pack as input for
> > "git-repack -a -d -f".
> >
> > 'next' 137.13 real 95.82 user 25.24 sys
> > 'next'+patch 131.62 real 89.35 user 28.56 sys
> >
> > but even if the running time was an extra 6 seconds I'd still rather
> > spend 4% more running time to use 1/2 the storage space.
> >
> >
> > diff --git a/pack-objects.c b/pack-objects.c
> > index 09f4f2c..f7d6217 100644
> > --- a/pack-objects.c
> > +++ b/pack-objects.c
> > @@ -1052,7 +1052,7 @@ static int try_delta(struct unpacked *cu
> > if (cur_entry->delta)
> > max_size = cur_entry->delta_size-1;
> > if (sizediff >= max_size)
> > - return -1;
> > + return 0;
> > delta_buf = diff_delta(old->data, oldsize,
> > cur->data, size, &delta_size, max_size);
> > if (!delta_buf)
>
> I can confirm this is indeed the best fix so far. Any "smarter"
> solution I could think of did increase the size of the final pack quite
> spectacularly and rather unexpectedly with Shawn's repository.
Wow. I'm such a trouble maker. *grin*
> Of course removing the if (sizediff >= max_size) entirely does produce a
> smaller pack (39MB) but it takes about twice the CPU.
Eh, that's not worth it. 7M disk space saved for twice the work isn't
that good of a tradeoff. I'm not in favor of that version.
> With the patch above the Linux kernel pack is 0.3% smaller with 1% more
> CPU usage. But like for the diff-delta hash list limiting code this
> small overhead is certainly a good compromize to avoid big degradations
> in some other cases.
Hmm. See the email I just sent. I was seeing a good 10% increase
in my own tests on a Linux kernel repository. But I guess I can
hope that my test was flawed somehow and it really is closer to a 1%
increase in running time, making it more likely that the above fix
makes it into GIT.
--
Shawn.
next prev parent reply other threads:[~2006-04-21 2:40 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-20 13:36 1.3.0 creating bigger packs than 1.2.3 Shawn Pearce
2006-04-20 14:47 ` Linus Torvalds
2006-04-20 15:03 ` Shawn Pearce
2006-04-20 16:07 ` Linus Torvalds
2006-04-20 16:43 ` Shawn Pearce
2006-04-20 17:03 ` Linus Torvalds
2006-04-20 17:24 ` Junio C Hamano
2006-04-20 17:31 ` Shawn Pearce
2006-04-20 17:54 ` Nicolas Pitre
2006-04-20 21:31 ` Junio C Hamano
2006-04-20 21:53 ` Shawn Pearce
2006-04-20 21:56 ` Jakub Narebski
2006-04-20 17:41 ` Nicolas Pitre
2006-04-20 17:55 ` Shawn Pearce
2006-04-20 18:24 ` Nicolas Pitre
2006-04-20 18:49 ` Junio C Hamano
2006-04-20 21:02 ` Nicolas Pitre
2006-04-20 21:40 ` Junio C Hamano
2006-04-20 22:02 ` Shawn Pearce
2006-04-20 22:35 ` Junio C Hamano
2006-04-21 1:01 ` Shawn Pearce
2006-04-20 22:59 ` Linus Torvalds
2006-04-21 0:52 ` Nicolas Pitre
2006-04-21 1:20 ` Shawn Pearce
2006-04-21 2:28 ` Nicolas Pitre
2006-04-21 2:40 ` Shawn Pearce [this message]
2006-04-21 3:07 ` Nicolas Pitre
2006-04-21 2:32 ` Shawn Pearce
2006-04-20 23:02 ` Junio C Hamano
2006-04-20 16:09 ` Nicolas Pitre
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