From: Stefan Beller <sbeller@google.com>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH] submodule: use cheaper check for submodule pushes
Date: Thu, 13 Jul 2017 13:54:04 -0700 [thread overview]
Message-ID: <CAGZ79kZouNBxOKr7X8j6wqebp3Wh3cDqhYR-t_PxaF7AwQ0Wzg@mail.gmail.com> (raw)
In-Reply-To: <20170713204854.GA158114@aiede.mtv.corp.google.com>
On Thu, Jul 13, 2017 at 1:48 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Hi,
>
> Stefan Beller wrote:
>
>> Yes we are safe, because the function itself only spawns a child process
>> (not using any of the objects).
>>
>> It's only caller push_unpushed_submodules also doesn't rely on objects
>> loaded after calling push_submodule.
>>
>> The caller of push_unpushed_submodules (transport.c, transport_push)
>> also doesn't need submodule objects loaded.
>
> Thanks for looking into it. This is what the commit message should
> say to help reviewers or people trying to understand it later. The
> footnotes don't help and are distracting, except that it makes sense
> to point out the original GSoC patch to say the alternate submodule
> odb wasn't needed even then.
>
> E.g.:
>
> Subject: push: do not add submodule odb as an alternate when recursing on demand
>
> "git push --recurse-submodules=on-demand" adds each submodule as an
> alternate with add_submodule_odb before checking whether the
> submodule has anything to push and pushing it if so.
>
> However, it never accesses any objects from the submodule. In the
> parent process it uses the submodule's ref database to see if there
> is anything to push. The actual push (which does rely on objects)
> occurs in a child process.
>
> The same was try when this call was originally added in
> v1.7.11-rc0~111^2 (push: teach --recurse-submodules the on-demand
> option, 2012-03-29). Most likely it was added by analogy with
> fetch --recurse-submodules=on-demand, which did use the submodule's
> object database.
>
> Use is_submodule_populated_gently instead, which is simpler and
> cheaper.
Thanks for giving a good example of commit message that I could use
in a reroll.
> With such a commit message change, this seems like a reasonable change
> in principle (though I haven't looked carefully to verify it).
>
> My one doubt is the is_submodule_populated_gently. Why are we using
> that instead of simpler is_submodule_populated? The names and API
> comments don't explain.
One could posit this is laziness of thinking.
See 15cdc64776 (make is_submodule_populated gently, 2017-03-14),
and discover there is no non-gentle version of is_submodule_populated.
And for each new use, it may be cheaper to just use the gentle version
instead of adding a non-gentle version.
Thanks,
Stefan
next prev parent reply other threads:[~2017-07-13 20:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-12 23:45 [PATCH] submodule: use cheaper check for submodule pushes Stefan Beller
2017-07-13 0:01 ` Jonathan Nieder
2017-07-13 0:09 ` Stefan Beller
2017-07-13 0:53 ` Junio C Hamano
2017-07-13 5:14 ` Stefan Beller
2017-07-13 18:37 ` Junio C Hamano
2017-07-13 19:39 ` Stefan Beller
2017-07-13 20:48 ` Jonathan Nieder
2017-07-13 20:54 ` Stefan Beller [this message]
2017-08-15 22:43 ` [PATCH] push: do not add submodule odb as an alternate when recursing on demand Stefan Beller
2017-08-15 23:10 ` Jonathan Nieder
2017-08-15 23:14 ` Jonathan Nieder
2017-08-15 23:27 ` Stefan Beller
2017-08-15 23:23 ` Junio C Hamano
2017-08-15 23:31 ` Stefan Beller
2017-08-16 0:11 ` Junio C Hamano
2017-08-16 1:05 ` Stefan Beller
2017-08-16 2:08 ` Jonathan Nieder
2017-08-16 5:52 ` Stefan Beller
2017-08-16 16:35 ` Heiko Voigt
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