From: Jakub Narebski <jnareb@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Mike Hommey" <mh@glandium.org>,
"SZEDER Gábor" <szeder.dev@gmail.com>,
git@vger.kernel.org
Subject: Re: Revision walking, commit dates, slop
Date: Mon, 20 May 2019 13:02:36 +0200 [thread overview]
Message-ID: <86mujhpewj.fsf@gmail.com> (raw)
In-Reply-To: <f14799c3-e343-eb41-3536-65de7e38fbd9@gmail.com> (Derrick Stolee's message of "Sun, 19 May 2019 21:33:08 -0400")
Derrick Stolee <stolee@gmail.com> writes:
> On 5/18/2019 12:17 AM, Mike Hommey wrote:
>> On Sat, May 18, 2019 at 12:58:28PM +0900, Mike Hommey wrote:
>>> On Sat, May 18, 2019 at 03:50:05AM +0200, SZEDER Gábor wrote:
>>>>
>>>> All the above is without commit-graph, I presume? If so, then you
>>>> should give it a try, as it might bring immediate help in your
>>>> pathological repo. With 5k commit in the same second (enforced via
>>>> 'export GIT_COMMITTER_DATE=$(date); for i in {1..5000} ...') I get:
>>>>
>>>> $ best-of-five -q git rev-list HEAD~..HEAD
>>>> 0.069
>>>> $ git commit-graph write --reachableComputing commit graph generation
>>>> numbers: 100% (5000/5000), done.
>>>> $ best-of-five -q git rev-list HEAD~..HEAD
>>>> 0.004
>>>
>>> I'm not observing any difference from using commit-graph, whether in
>>> time or in the number of commits that are looked at in limit_list().
>>
>> -c core.commitGraph=true does make a difference in time, but not in the
>> number of commits looked at in limit_list(). So it's only faster because
>> each iteration of the loop is faster. It means it's still dependent on
>> the depth of the dag, and the larger the repo will grow, the slower it
>> will get.
>
> The plan is to use the commit-graph's generation numbers for these A..B
> queries, but due to some cases when commit date is a _better_ heuristic
> than generation numbers, we have not enabled them for A..B. You'll see
> that 'git rev-list --topo-order -n 1 HEAD` will be much faster with the
> commit-graph, but adding '--topo-order' to your 'HEAD~1..HEAD' query
> should not change the time at all.
>
> See [1] for the discussion about "generation number v2" which will allow
> us to use a better heuristic in these cases.
>
> [1] https://public-inbox.org/git/6367e30a-1b3a-4fe9-611b-d931f51effef@gmail.com/
Are there any blockers that prevent the switch to this
"generation number v2"?
- Is it a problem with insufficient data to choose the correct numbering
as "generation number v2' (there can be only one)?
- Is it a problem with selected "generation number v2" being
incompatibile with gen v2, and Git failing when new version of
commit-graph is used instead of softly just not using commit-graph?
- Or is it something else?
Best,
--
Jakub Narębski
next prev parent reply other threads:[~2019-05-20 11:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-18 0:54 Revision walking, commit dates, slop Mike Hommey
2019-05-18 1:50 ` SZEDER Gábor
2019-05-18 3:58 ` Mike Hommey
2019-05-18 4:17 ` Mike Hommey
2019-05-18 12:01 ` SZEDER Gábor
2019-05-19 22:28 ` Jakub Narebski
2019-05-20 1:33 ` Derrick Stolee
2019-05-20 11:02 ` Jakub Narebski [this message]
2019-05-20 11:20 ` Derrick Stolee
2019-05-20 13:42 ` Jakub Narebski
2019-05-20 23:27 ` Jakub Narebski
2019-05-21 1:20 ` Derrick Stolee
2019-05-22 18:29 ` Jakub Narebski
2019-05-22 19:06 ` Derrick Stolee
2019-05-23 21:04 ` Jakub Narebski
2019-06-25 7:51 ` Jakub Narebski
2019-06-25 10:54 ` Derrick Stolee
2019-09-18 8:43 ` [RFC/PATCH] commit-graph: generation v5 (backward compatible date ceiling) Jakub Narebski
2019-09-18 12:26 ` Derrick Stolee
2019-05-21 13:14 ` [PATCH] revision: use generation for A..B --topo-order queries Derrick Stolee
2019-05-21 13:59 ` [PATCH 2/2] revision: keep topo-walk free of unintersting commits Derrick Stolee
2019-05-22 2:19 ` Mike Hommey
2019-05-21 2:00 ` Revision walking, commit dates, slop Jonathan Nieder
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