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From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: upload-pack is slow with lots of refs
Date: Wed, 3 Oct 2012 19:21:15 -0400	[thread overview]
Message-ID: <20121003232115.GB11618@sigill.intra.peff.net> (raw)
In-Reply-To: <CACBZZX4Fb0OCkh5kwKvLC+_0xb7q-UB7LH2_WY=dFN5SYUeezQ@mail.gmail.com>

On Thu, Oct 04, 2012 at 12:32:35AM +0200, Ævar Arnfjörð Bjarmason wrote:

> On Wed, Oct 3, 2012 at 8:03 PM, Jeff King <peff@peff.net> wrote:
> > What version of git are you using?  In the past year or so, I've made
> > several tweaks to speed up large numbers of refs, including:
> >
> >   - cff38a5 (receive-pack: eliminate duplicate .have refs, v1.7.6); note
> >     that this only helps if they are being pulled in by an alternates
> >     repo. And even then, it only helps if they are mostly duplicates;
> >     distinct ones are still O(n^2).
> >
> >   - 7db8d53 (fetch-pack: avoid quadratic behavior in remove_duplicates)
> >     a0de288 (fetch-pack: avoid quadratic loop in filter_refs)
> >     Both in v1.7.11. I think there is still a potential quadratic loop
> >     in mark_complete()
> >
> >   - 90108a2 (upload-pack: avoid parsing tag destinations)
> >     926f1dd (upload-pack: avoid parsing objects during ref advertisement)
> >     Both in v1.7.10. Note that tag objects are more expensive to
> >     advertise than commits, because we have to load and peel them.
> >
> > Even with those patches, though, I found that it was something like ~2s
> > to advertise 100,000 refs.
> 
> FWIW I bisected between 1.7.9 and 1.7.10 and found that the point at
> which it went from 1.5/s to 2.5/s upload-pack runs on the pathological
> git.git repository was none of those, but:
> 
>     ccdc6037fe - parse_object: try internal cache before reading object db

Ah, yeah, I forgot about that one. That implies that you have a lot of
refs pointing to the same objects (since the benefit of that commit is
to avoid reading from disk when we have already seen it).

Out of curiosity, what does your repo contain? I saw a lot of speedup
with that commit because my repos are big object stores, where we have
the same duplicated tag refs for every fork of the repo.

-Peff

  reply	other threads:[~2012-10-04 21:53 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-03 12:36 Ævar Arnfjörð Bjarmason
2012-10-03 13:06 ` Nguyen Thai Ngoc Duy
2012-10-03 18:03 ` Jeff King
2012-10-03 18:53   ` Junio C Hamano
2012-10-03 18:55     ` Jeff King
2012-10-03 19:41       ` Shawn Pearce
2012-10-03 20:13         ` Jeff King
2012-10-04 21:52           ` Sascha Cunz
2012-10-05  0:20             ` Jeff King
2012-10-05  6:24         ` Johannes Sixt
2012-10-05 16:57           ` Shawn Pearce
2012-10-08 15:05             ` Johannes Sixt
2012-10-09  6:46               ` Shawn Pearce
2012-10-09 20:30                 ` Johannes Sixt
2012-10-09 20:46                   ` Johannes Sixt
2012-10-03 20:16   ` Ævar Arnfjörð Bjarmason
2012-10-03 21:20     ` Jeff King
2012-10-03 22:15       ` Ævar Arnfjörð Bjarmason
2012-10-03 23:15         ` Jeff King
2012-10-03 23:54           ` Ævar Arnfjörð Bjarmason
2012-10-04  7:56             ` [PATCH 0/4] optimizing upload-pack ref peeling Jeff King
2012-10-04  7:58               ` [PATCH 1/4] peel_ref: use faster deref_tag_noverify Jeff King
2012-10-04 18:24                 ` Junio C Hamano
2012-10-04  8:00               ` [PATCH 2/4] peel_ref: do not return a null sha1 Jeff King
2012-10-04 18:32                 ` Junio C Hamano
2012-10-04  8:02               ` [PATCH 3/4] peel_ref: check object type before loading Jeff King
2012-10-04 19:06                 ` Junio C Hamano
2012-10-04 19:41                   ` Jeff King
2012-10-04 20:41                     ` Junio C Hamano
2012-10-04 21:59                       ` Jeff King
2012-10-04  8:03               ` [PATCH 4/4] upload-pack: use peel_ref for ref advertisements Jeff King
2012-10-04  8:04               ` [PATCH 0/4] optimizing upload-pack ref peeling Jeff King
2012-10-04  9:01                 ` Ævar Arnfjörð Bjarmason
2012-10-04 12:14                   ` Nazri Ramliy
2012-10-03 22:32   ` upload-pack is slow with lots of refs Ævar Arnfjörð Bjarmason
2012-10-03 23:21     ` Jeff King [this message]
2012-10-03 23:47       ` Ævar Arnfjörð Bjarmason
2012-10-03 19:13 ` Junio C Hamano

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