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From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "René Scharfe" <l.s.r@web.de>, "Git List" <git@vger.kernel.org>,
	"Martin Ågren" <martin.agren@gmail.com>,
	"Christian Couder" <christian.couder@gmail.com>
Subject: Re: [PATCH] revision: introduce prepare_revision_walk_extended()
Date: Tue, 19 Dec 2017 10:33:55 -0800	[thread overview]
Message-ID: <xmqq7etiworw.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20171219114906.GB24558@sigill.intra.peff.net> (Jeff King's message of "Tue, 19 Dec 2017 06:49:06 -0500")

Jeff King <peff@peff.net> writes:

> On Mon, Dec 18, 2017 at 08:18:19PM +0100, René Scharfe wrote:
>
>> > The root of the matter is that the revision-walking code doesn't clean
>> > up after itself. In every case, the caller is just saving these to clean
>> > up commit marks, isn't it?
>> 
>> bundle also checks if the pending objects exists.
>
> Thanks, I missed that one. So just adding a feature to clean up commit
> marks wouldn't be sufficient to cover that case.

OK.

>> > That sidesteps all of the memory ownership issues by just creating a
>> > copy. That's less efficient, but I'd be surprised if it matters in
>> > practice (we tend to do one or two revisions per process, there don't
>> > tend to be a lot of pending tips, and we're really just talking about
>> > copying some pointers here).
>> [...]
>> I don't know if there can be real-world use cases with millions of
>> entries (when it would start to hurt).
>
> I've seen repos which have tens of thousands of tags. Something like
> "rev-list --all" would have tens of thousands of pending objects.
> I think in practice it's limited to the number of objects (though in
> practice more like the number of commits).
> ...

OK again; that is an argument against "let's copy the array".

>> Why does prepare_revision_walk() clear the list of pending objects at
>> all?  Assuming the list is append-only then perhaps remembering the
>> last handled index would suffice.

For that matter, why does it copy, instead of using revs->pending
directly?  I do not think I can answer this, as I think the design
decisions led to this code predates me.

In any case, it seems that the discussion has veered into an
interesting tangent but at this point it seems to me that it is not
likely to produce an immediate improvement over the posted patch.

Should we take the patch posted as-is and move forward?

  reply	other threads:[~2017-12-19 18:34 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-16 12:12 René Scharfe
2017-12-17 10:20 ` Martin Ågren
2017-12-18 15:10 ` Jeff King
2017-12-18 19:18   ` René Scharfe
2017-12-19 11:49     ` Jeff King
2017-12-19 18:33       ` Junio C Hamano [this message]
2017-12-20 13:08         ` Jeff King
2017-12-21 18:41           ` René Scharfe
2017-12-24 14:22             ` Jeff King
2017-12-25 17:36               ` René Scharfe
2017-12-25 17:41 ` [PATCH v2 0/9] revision: get rid of the flag leak_pending René Scharfe
2017-12-25 17:43   ` [PATCH v2 1/9] commit: avoid allocation in clear_commit_marks_many() René Scharfe
2018-01-10  7:54     ` Jeff King
2017-12-25 17:44   ` [PATCH v2 2/9] commit: use clear_commit_marks_many() in remove_redundant() René Scharfe
2017-12-25 17:44   ` [PATCH v2 3/9] ref-filter: use clear_commit_marks_many() in do_merge_filter() René Scharfe
2017-12-25 17:44   ` [PATCH v2 4/9] object: add clear_commit_marks_all() René Scharfe
2018-01-10  7:58     ` Jeff King
2018-01-11 18:57       ` René Scharfe
2018-01-12 15:20         ` Jeff King
2017-12-25 17:45   ` [PATCH v2 5/9] bisect: avoid using the rev_info flag leak_pending René Scharfe
2018-01-10  8:07     ` Jeff King
2018-01-11 18:57       ` René Scharfe
2018-01-12 15:23         ` Jeff King
2017-12-25 17:46   ` [PATCH v2 6/9] bundle: " René Scharfe
2017-12-28 21:13     ` Junio C Hamano
2018-01-10  8:18     ` Jeff King
2017-12-25 17:47   ` [PATCH v2 7/9] checkout: " René Scharfe
2017-12-28 21:24     ` Junio C Hamano
2017-12-25 17:47   ` [PATCH v2 8/9] revision: remove the unused " René Scharfe
2017-12-25 17:48   ` [PATCH v2 9/9] commit: remove unused function clear_commit_marks_for_object_array() René Scharfe
2017-12-28 20:32   ` [PATCH v2 0/9] revision: get rid of the flag leak_pending Junio C Hamano
2018-01-10  8:20   ` Jeff King

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