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From: Jeff King <peff@peff.net>
To: "René Scharfe" <l.s.r@web.de>
Cc: "Git List" <git@vger.kernel.org>,
	"Martin Ågren" <martin.agren@gmail.com>,
	"Christian Couder" <christian.couder@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>
Subject: Re: [PATCH v2 4/9] object: add clear_commit_marks_all()
Date: Fri, 12 Jan 2018 10:20:59 -0500	[thread overview]
Message-ID: <20180112152058.GA10210@sigill.intra.peff.net> (raw)
In-Reply-To: <a0ca86b8-e258-2588-1c99-a30e8e60fdbd@web.de>

On Thu, Jan 11, 2018 at 07:57:42PM +0100, René Scharfe wrote:

> > Is it worth having:
> > 
> >    void clear_object_flags_from_type(int type, unsigned flags);
> > 
> > rather than having two near-identical functions? I guess we'd need some
> > way of saying "all types" to reimplement clear_object_flags() as a
> > wrapper (OBJ_NONE, I guess?).
> 
> I don't know if there is a demand.  Perhaps the two callers of
> clear_object_flags() should be switched to clear_commit_marks_all()?
> They look like they only care about commits as well.  Or is it safe to
> stomp over the flags of objects of other types?  Then we'd only need
> to keep clear_object_flags()..

I'd worry that the call in reset_revision_walk() might want to clear
non-commits if the revisions have "--objects" passed to them.

I do suspect that clearing flags from all objects would just work in the
general case (since we're limiting ourselves to only a particular set of
flags). But it's probably not worth the risk of unintended fallout,
since there's not much benefit after your series.

> > The run-time check is maybe a little bit slower in the middle of a tight
> > loop, but I'm not sure it would matter much (I'd actually be curious if
> > this approach is faster than the existing traversal code, too).
> 
> I don't know how to measure this properly.  With 100 runs each I get
> this for the git repo and the silly test program below, which measures
> the duration of the respective function call:
> 
>    mean        stddev method
>    ----------- ------ ----------------------
>    5.89763e+06 613106 clear_commit_marks
>    2.72572e+06 507689 clear_commit_marks_all
>    1.96582e+06 494753 clear_object_flags
> 
> So these are noisy numbers, but kind of in the expected range.

That's about what I'd expect. The "bad" case for looking at all objects
is when there are a bunch of objects loaded that _weren't_ part of this
particular traversal. I have no idea how often that happens, but we can
guess at the impact in the worst case: having done a previous --objects
traversal in the process and then traversing all of the commits a second
time, we'd probably have about 5-10x as many objects to look through for
that second path. So clear_commit_marks() would win there.

The absolute numbers are small enough that it probably doesn't matter
either way.

-Peff

  reply	other threads:[~2018-01-12 15:21 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-16 12:12 [PATCH] revision: introduce prepare_revision_walk_extended() 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
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 [this message]
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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