From: Derrick Stolee <stolee@gmail.com>
To: Jakub Narebski <jnareb@gmail.com>
Cc: "Derrick Stolee" <dstolee@microsoft.com>,
git@vger.kernel.org, "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Stefan Beller" <sbeller@google.com>,
"Lars Schneider" <larsxschneider@gmail.com>,
"Jeff King" <peff@peff.net>
Subject: Re: [PATCH 0/6] Compute and consume generation numbers
Date: Mon, 23 Apr 2018 09:54:56 -0400 [thread overview]
Message-ID: <68cadcfc-5fed-9c2c-8f5c-034ec64a347e@gmail.com> (raw)
In-Reply-To: <86d0yscmra.fsf@gmail.com>
On 4/21/2018 4:44 PM, Jakub Narebski wrote:
> Jakub Narebski <jnareb@gmail.com> writes:
>> Derrick Stolee <stolee@gmail.com> writes:
>>> On 4/11/2018 3:32 PM, Jakub Narebski wrote:
>>>> What would you suggest as a good test that could imply performance? The
>>>> Google Colab notebook linked to above includes a function to count
>>>> number of commits (nodes / vertices in the commit graph) walked,
>>>> currently in the worst case scenario.
>>> The two main questions to consider are:
>>>
>>> 1. Can X reach Y?
>> That is easy to do. The function generic_is_reachable() does
>> that... though using direct translation of the pseudocode for
>> "Algorithm 3: Reachable" from FELINE paper, which is recursive and
>> doesn't check if vertex was already visited was not good idea for large
>> graphs such as Linux kernel commit graph, oops. That is why
>> generic_is_reachable_large() was created.
> [...]
>
>>> And the thing to measure is a commit count. If possible, it would be
>>> good to count commits walked (commits whose parent list is enumerated)
>>> and commits inspected (commits that were listed as a parent of some
>>> walked commit). Walked commits require a commit parse -- albeit from
>>> the commit-graph instead of the ODB now -- while inspected commits
>>> only check the in-memory cache.
> [...]
>>> For git.git and Linux, I like to use the release tags as tests. They
>>> provide a realistic view of the linear history, and maintenance
>>> releases have their own history from the major releases.
>> Hmmm... testing for v4.9-rc5..v4.9 in Linux kernel commit graphs, the
>> FELINE index does not bring any improvements over using just level
>> (generation number) filter. But that may be caused by narrowing od
>> commit DAG around releases.
>>
>> I try do do the same between commits in wide part, with many commits
>> with the same level (same generation number) both for source and for
>> target commit. Though this may be unfair to level filter, though...
>>
>>
>> Note however that FELINE index is not unabiguous, like generation
>> numbers are (modulo decision whether to start at 0 or at 1); it depends
>> on the topological ordering chosen for the X elements.
> One can now test reachability on git.git repository; there is a form
> where one can plug source and destination revisions at
> https://colab.research.google.com/drive/1V-U7_slu5Z3s5iEEMFKhLXtaxSu5xyzg#scrollTo=svNUnSA9O_NK&line=2&uniqifier=1
>
> I have tried the case that is quite unfair to the generation numbers
> filter, namely the check between one of recent tags, and one commit that
> shares generation number among largest number of other commits.
>
> Here level = generation number-1 (as it starts at 0 for root commit, not
> 1).
>
> The results are:
> * src = 468165c1d = v2.17.0
> * dst = 66d2e04ec = v2.0.5-5-g66d2e04ec
>
> * 468165c1d has level 18418 which it shares with 6 commits
> * 66d2e04ec has level 14776 which it shares with 93 commits
> * gen(468165c1d) - gen(66d2e04ec) = 3642
>
> algorithm | access | walk | maxdepth | visited | level-f | FELINE-f |
> -----------+---------+--------+----------+---------+----------+-----------+
> naive | 48865 | 39599 | 244 | 9200 | | |
> level | 3086 | 2492 | 113 | 528 | 285 | |
> FELINE | 283 | 216 | 68 | 0 | | 25 |
> lev+FELINE | 282 | 215 | 68 | 0 | 5 | 24 |
> -----------+---------+--------+----------+---------+----------+-----------+
> lev+FEL+mpi| 79 | 59 | 21 | 0 | 0 | 0 |
>
> Here we have:
> * 'naive' implementation means simple DFS walk, without any filters (cut-offs)
> * 'level' means using levels / generation numbers based negative-cut filter
> * 'FELINE' means using FELINE index based negative-cut filter
> * 'lev+FELINE' means combining generation numbers filter with FELINE filter
> * 'mpi' means min-post [smanning-tree] intervals for positive-cut filter;
> note that the code does not walk the path after cut, but it is easy to do
>
> The stats have the following meaning:
> * 'access' means accessing the node
> * 'walk' is actual walking the node
> * 'maxdepth' is maximum depth of the stack used for DFS
> * 'level-f' and 'FELINE-f' is number of times levels filter or FELINE filter
> were used for negative-cut; note that those are not disjoint; node can
> be rejected by both level filter and FELINE filter
>
> For v2.17.0 and v2.17.0-rc2 the numbers are much less in FELINE favor:
> the results are the same, with 5 commits accessed and 6 walked compared
> to 61574 accessed in naive algorithm.
>
> The git.git commit graph has 53128 nodes and 66124 edges, 4 tips / heads
> (different child-less commits) and 9 roots, and has average clustering
> coefficient 0.000409217.
Thanks for these results. Now, write a patch. I'm sticking to generation
numbers for my patch because of the simplified computation, but you can
contribute a FELINE implementation.
> P.S. Would it be better to move the discussion about possible extensions
> to the commit-graph in the form of new chunks (topological order, FELINE
> index, min-post intervals, bloom filter for changed files, etc.) be
> moved into separate thread?
Yes. I think we've exhausted this thought experiment and future
discussion should revolve around actual implementations in Git with
end-to-end performance times. The computation time for computing the
FELINE index should be included in that discussion.
Thanks,
-Stolee
next prev parent reply other threads:[~2018-04-23 13:55 UTC|newest]
Thread overview: 162+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-03 16:51 [PATCH 0/6] Compute and consume generation numbers Derrick Stolee
2018-04-03 16:51 ` [PATCH 1/6] object.c: parse commit in graph first Derrick Stolee
2018-04-03 18:21 ` Jonathan Tan
2018-04-03 18:28 ` Jeff King
2018-04-03 18:32 ` Derrick Stolee
2018-04-03 16:51 ` [PATCH 2/6] commit: add generation number to struct commmit Derrick Stolee
2018-04-03 18:05 ` Brandon Williams
2018-04-03 18:28 ` Jeff King
2018-04-03 18:31 ` Derrick Stolee
2018-04-03 18:32 ` Brandon Williams
2018-04-03 18:44 ` Stefan Beller
2018-04-03 23:17 ` Ramsay Jones
2018-04-03 23:19 ` Jeff King
2018-04-03 18:24 ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 3/6] commit-graph: compute generation numbers Derrick Stolee
2018-04-03 18:30 ` Jonathan Tan
2018-04-03 18:49 ` Stefan Beller
2018-04-03 16:51 ` [PATCH 4/6] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-03 18:31 ` Stefan Beller
2018-04-03 18:31 ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 5/6] commit.c: use generation to halt paint walk Derrick Stolee
2018-04-03 19:01 ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 6/6] commit-graph.txt: update future work Derrick Stolee
2018-04-03 19:04 ` Jonathan Tan
2018-04-03 16:56 ` [PATCH 0/6] Compute and consume generation numbers Derrick Stolee
2018-04-03 18:03 ` Brandon Williams
2018-04-03 18:29 ` Derrick Stolee
2018-04-03 18:47 ` Jeff King
2018-04-03 19:05 ` Jeff King
2018-04-04 15:45 ` [PATCH 7/6] ref-filter: use generation number for --contains Derrick Stolee
2018-04-04 15:45 ` [PATCH 8/6] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-04 15:48 ` Derrick Stolee
2018-04-04 17:01 ` Brandon Williams
2018-04-04 18:24 ` Jeff King
2018-04-04 18:53 ` Derrick Stolee
2018-04-04 18:59 ` Jeff King
2018-04-04 18:22 ` [PATCH 7/6] ref-filter: use generation number for --contains Jeff King
2018-04-04 19:06 ` Derrick Stolee
2018-04-04 19:16 ` Jeff King
2018-04-04 19:22 ` Derrick Stolee
2018-04-04 19:42 ` Jeff King
2018-04-04 19:45 ` Derrick Stolee
2018-04-04 19:46 ` Jeff King
2018-04-07 17:09 ` [PATCH 0/6] Compute and consume generation numbers Jakub Narebski
2018-04-07 16:55 ` Jakub Narebski
2018-04-08 1:06 ` Derrick Stolee
2018-04-11 19:32 ` Jakub Narebski
2018-04-11 19:58 ` Derrick Stolee
2018-04-14 16:52 ` Jakub Narebski
2018-04-21 20:44 ` Jakub Narebski
2018-04-23 13:54 ` Derrick Stolee [this message]
2018-04-09 16:41 ` [PATCH v2 00/10] " Derrick Stolee
2018-04-09 16:41 ` [PATCH v2 01/10] object.c: parse commit in graph first Derrick Stolee
2018-04-09 16:41 ` [PATCH v2 02/10] merge: check config before loading commits Derrick Stolee
2018-04-11 2:12 ` Junio C Hamano
2018-04-11 12:49 ` Derrick Stolee
2018-04-09 16:42 ` [PATCH v2 03/10] commit: add generation number to struct commmit Derrick Stolee
2018-04-09 17:59 ` Stefan Beller
2018-04-11 2:31 ` Junio C Hamano
2018-04-11 12:57 ` Derrick Stolee
2018-04-11 23:28 ` Junio C Hamano
2018-04-09 16:42 ` [PATCH v2 04/10] commit-graph: compute generation numbers Derrick Stolee
2018-04-11 2:51 ` Junio C Hamano
2018-04-11 13:02 ` Derrick Stolee
2018-04-11 18:49 ` Stefan Beller
2018-04-11 19:26 ` Eric Sunshine
2018-04-09 16:42 ` [PATCH v2 05/10] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-09 16:42 ` [PATCH v2 06/10] commit.c: use generation to halt paint walk Derrick Stolee
2018-04-11 3:02 ` Junio C Hamano
2018-04-11 13:24 ` Derrick Stolee
2018-04-09 16:42 ` [PATCH v2 07/10] commit-graph.txt: update future work Derrick Stolee
2018-04-12 9:12 ` Junio C Hamano
2018-04-12 11:35 ` Derrick Stolee
2018-04-13 9:53 ` Jakub Narebski
2018-04-09 16:42 ` [PATCH v2 08/10] ref-filter: use generation number for --contains Derrick Stolee
2018-04-09 16:42 ` [PATCH v2 09/10] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-09 16:42 ` [PATCH v2 10/10] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 0/9] Compute and consume generation numbers Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 1/9] commit: add generation number to struct commmit Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 2/9] commit-graph: compute generation numbers Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 3/9] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-18 14:31 ` Jakub Narebski
2018-04-18 14:46 ` Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 4/9] commit-graph.txt: update design document Derrick Stolee
2018-04-18 19:47 ` Jakub Narebski
2018-04-17 17:00 ` [PATCH v3 5/9] ref-filter: use generation number for --contains Derrick Stolee
2018-04-18 21:02 ` Jakub Narebski
2018-04-23 14:22 ` Derrick Stolee
2018-04-24 18:56 ` Jakub Narebski
2018-04-25 14:11 ` Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 6/9] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-18 22:15 ` Jakub Narebski
2018-04-23 14:31 ` Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 7/9] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-18 23:19 ` Jakub Narebski
2018-04-23 14:40 ` Derrick Stolee
2018-04-23 21:38 ` Jakub Narebski
2018-04-24 12:31 ` Derrick Stolee
2018-04-19 8:32 ` Jakub Narebski
2018-04-17 17:00 ` [PATCH v3 8/9] commit-graph: always load commit-graph information Derrick Stolee
2018-04-17 17:50 ` Derrick Stolee
2018-04-19 0:02 ` Jakub Narebski
2018-04-23 14:49 ` Derrick Stolee
2018-04-17 17:00 ` [PATCH v3 9/9] merge: check config before loading commits Derrick Stolee
2018-04-19 0:04 ` [PATCH v3 0/9] Compute and consume generation numbers Jakub Narebski
2018-04-23 14:54 ` Derrick Stolee
2018-04-25 14:37 ` [PATCH v4 00/10] " Derrick Stolee
2018-04-25 14:37 ` [PATCH v4 01/10] ref-filter: fix outdated comment on in_commit_list Derrick Stolee
2018-04-28 17:54 ` Jakub Narebski
2018-04-25 14:37 ` [PATCH v4 02/10] commit: add generation number to struct commmit Derrick Stolee
2018-04-28 22:35 ` Jakub Narebski
2018-04-30 12:05 ` Derrick Stolee
2018-04-25 14:37 ` [PATCH v4 03/10] commit-graph: compute generation numbers Derrick Stolee
2018-04-26 2:35 ` Junio C Hamano
2018-04-26 12:58 ` Derrick Stolee
2018-04-26 13:49 ` Derrick Stolee
2018-04-29 9:08 ` Jakub Narebski
2018-05-01 12:10 ` Derrick Stolee
2018-05-02 16:15 ` Jakub Narebski
2018-04-25 14:37 ` [PATCH v4 04/10] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-26 3:22 ` Junio C Hamano
2018-04-26 9:02 ` Jakub Narebski
2018-04-28 14:38 ` Jakub Narebski
2018-04-29 15:40 ` Jakub Narebski
2018-04-25 14:37 ` [PATCH v4 05/10] commit-graph: always load commit-graph information Derrick Stolee
2018-04-29 22:14 ` Jakub Narebski
2018-05-01 12:19 ` Derrick Stolee
2018-04-29 22:18 ` Jakub Narebski
2018-04-25 14:37 ` [PATCH v4 06/10] ref-filter: use generation number for --contains Derrick Stolee
2018-04-30 16:34 ` Jakub Narebski
2018-04-25 14:37 ` [PATCH v4 07/10] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-30 17:05 ` Jakub Narebski
2018-04-25 14:38 ` [PATCH v4 08/10] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-30 22:19 ` Jakub Narebski
2018-05-01 11:47 ` Derrick Stolee
2018-05-02 13:05 ` Jakub Narebski
2018-05-02 13:42 ` Derrick Stolee
2018-04-25 14:38 ` [PATCH v4 09/10] merge: check config before loading commits Derrick Stolee
2018-04-30 22:54 ` Jakub Narebski
2018-05-01 11:52 ` Derrick Stolee
2018-05-02 11:41 ` Jakub Narebski
2018-04-25 14:38 ` [PATCH v4 10/10] commit-graph.txt: update design document Derrick Stolee
2018-04-30 23:32 ` Jakub Narebski
2018-05-01 12:00 ` Derrick Stolee
2018-05-02 7:57 ` Jakub Narebski
2018-04-25 14:40 ` [PATCH v4 00/10] Compute and consume generation numbers Derrick Stolee
2018-04-28 17:28 ` Jakub Narebski
2018-05-01 12:47 ` [PATCH v5 00/11] " Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 01/11] ref-filter: fix outdated comment on in_commit_list Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 02/11] commit: add generation number to struct commmit Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 03/11] commit-graph: compute generation numbers Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 04/11] commit: use generations in paint_down_to_common() Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 05/11] commit-graph: always load commit-graph information Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 06/11] ref-filter: use generation number for --contains Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 07/11] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 08/11] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 09/11] commit: use generation number in remove_redundant() Derrick Stolee
2018-05-01 15:37 ` Derrick Stolee
2018-05-03 18:45 ` Jakub Narebski
2018-05-01 12:47 ` [PATCH v5 10/11] merge: check config before loading commits Derrick Stolee
2018-05-01 12:47 ` [PATCH v5 11/11] commit-graph.txt: update design document Derrick Stolee
2018-05-03 11:18 ` [PATCH v5 00/11] Compute and consume generation numbers Jakub Narebski
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