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From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
	"Jansen, Geert" <gerardu@amazon.com>,
	"git@vger.kernel.org" <git@vger.kernel.org>,
	Christian Couder <christian.couder@gmail.com>,
	Nicolas Pitre <nico@fluxnic.net>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH] index-pack: improve performance on NFS
Date: Mon, 29 Oct 2018 11:09:44 -0400	[thread overview]
Message-ID: <20181029150943.GI17668@sigill.intra.peff.net> (raw)
In-Reply-To: <20181029150453.GH17668@sigill.intra.peff.net>

On Mon, Oct 29, 2018 at 11:04:53AM -0400, Jeff King wrote:

> > Even if someone wants to make the argument that this is behavior that we
> > absolutely *MUST* keep and not make configurable, there's still much
> > smarter ways to do it.
> 
> I don't have any real object to a configuration like this, if people
> want to experiment with it. But in contrast, the patch I showed earlier:
> 
>   - is safe enough to just turn on all the time, without the user having
>     to configure anything nor make a safety tradeoff
> 
>   - speeds up all the other spots that use OBJECT_INFO_QUICK (like
>     fetch's tag-following, or what appears to be the exact same
>     optimization done manually inside mark_complete_and_common-ref()).

One thing I forgot to add. We're focusing here on the case where the
objects _aren't_ present, and we're primarily trying to get rid of the
stat call.

But when we actually do see a duplicate, we open up the object and
actually compare the bytes. Eliminating the collision check entirely
would save that work, which is obviously something that can't be
improved by just caching the existence of loose objects.

I'm not sure how often that case happens in a normal repository. We see
it a fair on GitHub servers because of the way we use alternates (i.e.,
we often already have the object you pushed up because it's present in
another fork and available via objects/info/alternates).

-Peff

  reply	other threads:[~2018-10-29 15:09 UTC|newest]

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-25 18:38 [RFC PATCH] index-pack: improve performance on NFS Jansen, Geert
2018-10-26  0:21 ` Junio C Hamano
2018-10-26 20:38   ` Ævar Arnfjörð Bjarmason
2018-10-27  7:26     ` Junio C Hamano
2018-10-27  9:33       ` Jeff King
2018-10-27 11:22         ` Ævar Arnfjörð Bjarmason
2018-10-28 22:50           ` [PATCH 0/4] index-pack: optionally turn off SHA-1 collision checking Ævar Arnfjörð Bjarmason
2018-10-30  2:49             ` Geert Jansen
2018-10-30  9:04               ` Junio C Hamano
2018-10-30 18:43             ` [PATCH v2 0/3] index-pack: test updates Ævar Arnfjörð Bjarmason
2018-11-13 20:19               ` [PATCH v3] index-pack: add ability to disable SHA-1 collision check Ævar Arnfjörð Bjarmason
2018-11-14  7:09                 ` Junio C Hamano
2018-11-14 12:40                   ` Ævar Arnfjörð Bjarmason
2018-10-30 18:43             ` [PATCH v2 1/3] pack-objects test: modernize style Ævar Arnfjörð Bjarmason
2018-10-30 18:43             ` [PATCH v2 2/3] pack-objects tests: don't leave test .git corrupt at end Ævar Arnfjörð Bjarmason
2018-10-30 18:43             ` [PATCH v2 3/3] index-pack tests: don't leave test repo dirty " Ævar Arnfjörð Bjarmason
2018-10-28 22:50           ` [PATCH 1/4] pack-objects test: modernize style Ævar Arnfjörð Bjarmason
2018-10-28 22:50           ` [PATCH 2/4] pack-objects tests: don't leave test .git corrupt at end Ævar Arnfjörð Bjarmason
2018-10-28 22:50           ` [PATCH 3/4] index-pack tests: don't leave test repo dirty " Ævar Arnfjörð Bjarmason
2018-10-28 22:50           ` [PATCH 4/4] index-pack: add ability to disable SHA-1 collision check Ævar Arnfjörð Bjarmason
2018-10-29 15:04           ` [RFC PATCH] index-pack: improve performance on NFS Jeff King
2018-10-29 15:09             ` Jeff King [this message]
2018-10-29 19:36             ` Ævar Arnfjörð Bjarmason
2018-10-29 23:27               ` Jeff King
2018-11-07 22:55                 ` Geert Jansen
2018-11-08 12:02                   ` Jeff King
2018-11-08 20:58                     ` Geert Jansen
2018-11-08 21:18                       ` Jeff King
2018-11-08 21:55                         ` Geert Jansen
2018-11-08 22:20                     ` Ævar Arnfjörð Bjarmason
2018-11-09 10:11                       ` Ævar Arnfjörð Bjarmason
2018-11-12 14:31                       ` Jeff King
2018-11-12 14:46                     ` [PATCH 0/9] caching loose objects Jeff King
2018-11-12 14:46                       ` [PATCH 1/9] fsck: do not reuse child_process structs Jeff King
2018-11-12 15:26                         ` Derrick Stolee
2018-11-12 14:47                       ` [PATCH 2/9] submodule--helper: prefer strip_suffix() to ends_with() Jeff King
2018-11-12 18:23                         ` Stefan Beller
2018-11-12 14:48                       ` [PATCH 3/9] rename "alternate_object_database" to "object_directory" Jeff King
2018-11-12 15:30                         ` Derrick Stolee
2018-11-12 15:36                           ` Jeff King
2018-11-12 19:41                             ` Ramsay Jones
2018-11-12 14:48                       ` [PATCH 4/9] sha1_file_name(): overwrite buffer instead of appending Jeff King
2018-11-12 15:32                         ` Derrick Stolee
2018-11-12 14:49                       ` [PATCH 5/9] handle alternates paths the same as the main object dir Jeff King
2018-11-12 15:38                         ` Derrick Stolee
2018-11-12 15:46                           ` Jeff King
2018-11-12 15:50                             ` Derrick Stolee
2018-11-12 14:50                       ` [PATCH 6/9] sha1-file: use an object_directory for " Jeff King
2018-11-12 15:48                         ` Derrick Stolee
2018-11-12 16:09                           ` Jeff King
2018-11-12 19:04                             ` Stefan Beller
2018-11-22 17:42                               ` Jeff King
2018-11-12 18:48                           ` Stefan Beller
2018-11-12 14:50                       ` [PATCH 7/9] object-store: provide helpers for loose_objects_cache Jeff King
2018-11-12 19:24                         ` René Scharfe
2018-11-12 20:16                           ` Jeff King
2018-11-12 14:54                       ` [PATCH 8/9] sha1-file: use loose object cache for quick existence check Jeff King
2018-11-12 16:00                         ` Derrick Stolee
2018-11-12 16:01                         ` Ævar Arnfjörð Bjarmason
2018-11-12 16:21                           ` Jeff King
2018-11-12 22:18                             ` Ævar Arnfjörð Bjarmason
2018-11-12 22:30                               ` Ævar Arnfjörð Bjarmason
2018-11-13 10:02                                 ` Ævar Arnfjörð Bjarmason
2018-11-14 18:21                                   ` René Scharfe
2018-12-02 10:52                                   ` René Scharfe
2018-12-03 22:04                                     ` Jeff King
2018-12-04 21:45                                       ` René Scharfe
2018-12-05  4:46                                         ` Jeff King
2018-12-05  6:02                                           ` René Scharfe
2018-12-05  6:51                                             ` Jeff King
2018-12-05  8:15                                               ` Jeff King
2018-12-05 18:41                                                 ` René Scharfe
2018-12-05 20:17                                                   ` Jeff King
2018-11-12 22:44                             ` Geert Jansen
2018-11-27 20:48                         ` René Scharfe
2018-12-01 19:49                           ` Jeff King
2018-11-12 14:55                       ` [PATCH 9/9] fetch-pack: drop custom loose object cache Jeff King
2018-11-12 19:25                         ` René Scharfe
2018-11-12 19:32                           ` Ævar Arnfjörð Bjarmason
2018-11-12 20:07                             ` Jeff King
2018-11-12 20:13                             ` René Scharfe
2018-11-12 16:02                       ` [PATCH 0/9] caching loose objects Derrick Stolee
2018-11-12 19:10                         ` Stefan Beller
2018-11-09 13:43                   ` [RFC PATCH] index-pack: improve performance on NFS Ævar Arnfjörð Bjarmason
2018-11-09 16:08                     ` Duy Nguyen
2018-11-10 14:04                       ` Ævar Arnfjörð Bjarmason
2018-11-12 14:34                         ` Jeff King
2018-11-12 22:58                     ` Geert Jansen
2018-10-27 14:04         ` Duy Nguyen
2018-10-29 15:18           ` Jeff King
2018-10-29  0:48         ` Junio C Hamano
2018-10-29 15:20           ` Jeff King
2018-10-29 18:43             ` Ævar Arnfjörð Bjarmason
2018-10-29 21:34           ` Geert Jansen
2018-10-29 21:50             ` Jeff King
2018-10-29 22:21               ` Geert Jansen
2018-10-29 22:27             ` Jeff King
2018-10-29 22:35               ` Stefan Beller
2018-10-29 23:29                 ` Jeff King

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