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From: Derrick Stolee <stolee@gmail.com>
To: Jeff King <peff@peff.net>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Stefan Beller" <sbeller@google.com>, git <git@vger.kernel.org>,
	"Duy Nguyen" <pclouds@gmail.com>
Subject: Re: Bloom Filters
Date: Thu, 11 Oct 2018 08:33:58 -0400	[thread overview]
Message-ID: <bcf5586e-d0b0-e5e2-0dff-fb4606ff91c4@gmail.com> (raw)
In-Reply-To: <20181009231250.GA19342@sigill.intra.peff.net>

On 10/9/2018 7:12 PM, Jeff King wrote:
> On Tue, Oct 09, 2018 at 05:14:50PM -0400, Jeff King wrote:
>
>> Hmph. It really sounds like we could do better with a custom RLE
>> solution. But that makes me feel like I'm missing something, because
>> surely I can't invent something better than the state of the art in a
>> simple thought experiment, right?
>>
>> I know what I'm proposing would be quite bad for random access, but my
>> impression is that EWAH is the same. For the scale of bitmaps we're
>> talking about, I think linear/streaming access through the bitmap would
>> be OK.
> Thinking on it more, what I was missing is that for truly dense random
> bitmaps, this will perform much worse. Because it will use a byte to say
> "there's one 1", rather than a bit.
>
> But I think it does OK in practice for the very sparse bitmaps we tend
> to see in this application.  I was able to generate a complete output
> that can reproduce "log --name-status -t" for linux.git in 32MB. But:
>
>    - 15MB of that is commit sha1s, which will be stored elsewhere in a
>      "real" system
>
>    - 5MB of that is path list (which should shrink by a factor of 10 with
>      prefix compression, and is really a function of a tree size less
>      than history depth)
>
> So the per-commit cost is not too bad. That's still not counting merges,
> though, which would add another 10-15% (or maybe more; their bitmaps are
> less sparse).
>
> I don't know if this is a fruitful path at all or not. I was mostly just
> satisfying my own curiosity on the bitmap encoding question. But I'll
> post the patches, just to show my work. The first one is the same
> initial proof of concept I showed earlier.
>
>    [1/3]: initial tree-bitmap proof of concept
>    [2/3]: test-tree-bitmap: add "dump" mode
>    [3/3]: test-tree-bitmap: replace ewah with custom rle encoding
>
>   Makefile                    |   1 +
>   t/helper/test-tree-bitmap.c | 344 ++++++++++++++++++++++++++++++++++++
>   2 files changed, 345 insertions(+)
>   create mode 100644 t/helper/test-tree-bitmap.c
I'm trying to test this out myself, and am having trouble reverse 
engineering how I'm supposed to test it.

Looks like running "t/helper/test-tree-bitmap gen" will output a lot of 
binary data. Where should I store that? Does any file work?

Is this series just for the storage costs, assuming that we would 
replace all TREESAME checks with a query into this database? Or do you 
have a way to test how much this would improve a "git log -- <path>" query?

Thanks,
-Stolee

  parent reply	other threads:[~2018-10-11 12:34 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-03 13:23 We should add a "git gc --auto" after "git clone" due to commit graph Ævar Arnfjörð Bjarmason
2018-10-03 13:36 ` SZEDER Gábor
2018-10-03 13:42   ` Derrick Stolee
2018-10-03 14:18     ` Ævar Arnfjörð Bjarmason
2018-10-03 14:01   ` Ævar Arnfjörð Bjarmason
2018-10-03 14:17     ` SZEDER Gábor
2018-10-03 14:22       ` Ævar Arnfjörð Bjarmason
2018-10-03 14:53         ` SZEDER Gábor
2018-10-03 15:19           ` Ævar Arnfjörð Bjarmason
2018-10-03 16:59             ` SZEDER Gábor
2018-10-05  6:09               ` Junio C Hamano
2018-10-10 22:07                 ` SZEDER Gábor
2018-10-10 23:01                   ` Ævar Arnfjörð Bjarmason
2018-10-03 19:08           ` Stefan Beller
2018-10-03 19:21             ` Jeff King
2018-10-03 20:35               ` Ævar Arnfjörð Bjarmason
2018-10-03 17:47         ` Stefan Beller
2018-10-03 18:47           ` Ævar Arnfjörð Bjarmason
2018-10-03 18:51             ` Jeff King
2018-10-03 18:59               ` Derrick Stolee
2018-10-03 19:18                 ` Jeff King
2018-10-08 16:41                   ` SZEDER Gábor
2018-10-08 16:57                     ` Derrick Stolee
2018-10-08 18:10                       ` SZEDER Gábor
2018-10-08 18:29                         ` Derrick Stolee
2018-10-09  3:08                           ` Jeff King
2018-10-09 13:48                             ` Bloom Filters (was Re: We should add a "git gc --auto" after "git clone" due to commit graph) Derrick Stolee
2018-10-09 18:45                               ` Ævar Arnfjörð Bjarmason
2018-10-09 18:46                               ` Jeff King
2018-10-09 19:03                                 ` Derrick Stolee
2018-10-09 21:14                                   ` Jeff King
2018-10-09 23:12                                     ` Bloom Filters Jeff King
2018-10-09 23:13                                       ` [PoC -- do not apply 1/3] initial tree-bitmap proof of concept Jeff King
2018-10-09 23:14                                       ` [PoC -- do not apply 2/3] test-tree-bitmap: add "dump" mode Jeff King
2018-10-10  0:48                                         ` Junio C Hamano
2018-10-11  3:13                                           ` Jeff King
2018-10-09 23:14                                       ` [PoC -- do not apply 3/3] test-tree-bitmap: replace ewah with custom rle encoding Jeff King
2018-10-10  0:58                                         ` Junio C Hamano
2018-10-11  3:20                                           ` Jeff King
2018-10-11 12:33                                       ` Derrick Stolee [this message]
2018-10-11 13:43                                         ` Bloom Filters Jeff King
2018-10-09 21:30                             ` We should add a "git gc --auto" after "git clone" due to commit graph SZEDER Gábor
2018-10-09 19:34                       ` [PATCH 0/4] Bloom filter experiment SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 1/4] Add a (very) barebones Bloom filter implementation SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 2/4] commit-graph: write a Bloom filter containing changed paths for each commit SZEDER Gábor
2018-10-09 21:06                           ` Jeff King
2018-10-09 21:37                             ` SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 3/4] revision.c: use the Bloom filter to speed up path-limited revision walks SZEDER Gábor
2018-10-09 19:34                         ` [PATCH 4/4] revision.c: add GIT_TRACE_BLOOM_FILTER for a bit of statistics SZEDER Gábor
2018-10-09 19:47                         ` [PATCH 0/4] Bloom filter experiment Derrick Stolee
2018-10-11  1:21                         ` [PATCH 0/2] Per-commit filter proof of concept Jonathan Tan
2018-10-11  1:21                           ` [PATCH 1/2] One filter per commit Jonathan Tan
2018-10-11 12:49                             ` Derrick Stolee
2018-10-11 19:11                               ` [PATCH] Per-commit and per-parent filters for 2 parents Jonathan Tan
2018-10-11  1:21                           ` [PATCH 2/2] Only make bloom filter for first parent Jonathan Tan
2018-10-11  7:37                           ` [PATCH 0/2] Per-commit filter proof of concept Ævar Arnfjörð Bjarmason
2018-10-15 14:39                         ` [PATCH 0/4] Bloom filter experiment Derrick Stolee
2018-10-16  4:45                           ` Junio C Hamano
2018-10-16 11:13                             ` Derrick Stolee
2018-10-16 12:57                               ` Ævar Arnfjörð Bjarmason
2018-10-16 13:03                                 ` Derrick Stolee
2018-10-18  2:00                                 ` Junio C Hamano
2018-10-16 23:41                           ` Jonathan Tan
2018-10-08 23:02                     ` We should add a "git gc --auto" after "git clone" due to commit graph Junio C Hamano
2018-10-03 14:32     ` Duy Nguyen
2018-10-03 16:45 ` Duy Nguyen
2018-10-04 21:42 ` [RFC PATCH] " Ævar Arnfjörð Bjarmason
2018-10-05 12:05   ` Derrick Stolee
2018-10-05 13:05     ` Ævar Arnfjörð Bjarmason
2018-10-05 13:45       ` Derrick Stolee
2018-10-05 14:04         ` Ævar Arnfjörð Bjarmason
2018-10-05 19:21         ` Jeff King
2018-10-05 19:41           ` Derrick Stolee
2018-10-05 19:47             ` Jeff King
2018-10-05 20:00               ` Derrick Stolee
2018-10-05 20:02                 ` Jeff King
2018-10-05 20:01               ` Ævar Arnfjörð Bjarmason
2018-10-05 20:09                 ` Jeff King

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