From: Junio C Hamano <gitster@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Carlos R. Mafra" <crmafra2@gmail.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: Performance issue of 'git branch'
Date: Wed, 22 Jul 2009 22:52:17 -0700 [thread overview]
Message-ID: <7veis83q0e.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <alpine.LFD.2.01.0907222204310.21520@localhost.localdomain> (Linus Torvalds's message of "Wed\, 22 Jul 2009 22\:36\:09 -0700 \(PDT\)")
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Wed, 22 Jul 2009, Junio C Hamano wrote:
>>
>> Hmm, we now have to remember what this patch did, if we ever wanted to
>> introduce negative refs later (see ef06b91 do_for_each_ref: perform the
>> same sanity check for leftovers., 2006-11-18). Not exactly nice to spread
>> the codepaths that need to be updated.
> ...
> And since git branch will do something _better_ than the 'has_sha1_file()'
> check (by virtue of actually looking up the commit), I don't think that
> part is an issue. So the only issue is the is_null_sha1() thing.
Exactly.
That is_null_sha1() thing was a remnant of your idea to represent deleted
ref that has a packed counterpart by storing 0{40} in a loose ref, so that
we can implement deletion efficiently.
Since we currently implement deletion by repacking packed refs if the ref
has a packed (possibly stale) one, we do not use such a "negative ref",
and skipping 0{40} done by the normal (i.e. non-raw) for_each_ref() family
is not necessary.
I was inclined to say that, because I never saw anybody complained that
deleting refs was too slow, we declare that we would forever stick to the
current implementation of ref deletion, and remove the is_null_sha1()
check from the do_one_ref() function, even for include-broken case.
But after thinking about it again, I'd say "if null, then skip" should be
outside the DO_FOR_EACH_INCLUDE_BROKEN anyway, because the null check is
not about brokenness of the ref, but is about a possible future expansion
to represent deleted ref with such a "negative ref" entry.
If we remove is_null_sha1() from do_one_ref(), or if we move it out of the
"include broken" thing, my "Not exactly nice" comment can be rescinded, as
doing the former (i.e. removal of is_null_sha1() check) is a promise that
we will never have to worry about negative refs, and doing the latter will
still protect callers of do_for_each_rawref() from negative refs if we
ever introduce them in some future.
next prev parent reply other threads:[~2009-07-23 5:52 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-22 23:59 Performance issue of 'git branch' Carlos R. Mafra
2009-07-23 0:21 ` Linus Torvalds
2009-07-23 0:51 ` Linus Torvalds
2009-07-23 0:55 ` Linus Torvalds
2009-07-23 2:02 ` Carlos R. Mafra
2009-07-23 2:28 ` Linus Torvalds
2009-07-23 12:42 ` Jakub Narebski
2009-07-23 14:45 ` Carlos R. Mafra
2009-07-23 16:25 ` Linus Torvalds
2009-07-23 1:22 ` Carlos R. Mafra
2009-07-23 2:20 ` Linus Torvalds
2009-07-23 2:23 ` Linus Torvalds
2009-07-23 3:08 ` Linus Torvalds
2009-07-23 3:21 ` Linus Torvalds
2009-07-23 17:47 ` Tony Finch
2009-07-23 18:57 ` Linus Torvalds
2009-07-23 22:48 ` Newton-Raphson, was " Tony Finch
2009-07-23 23:24 ` Johannes Schindelin
2009-07-23 23:50 ` Tony Finch
2009-07-24 0:43 ` Johannes Schindelin
2009-07-23 3:18 ` Carlos R. Mafra
2009-07-23 3:27 ` Carlos R. Mafra
2009-07-23 3:40 ` Carlos R. Mafra
2009-07-23 3:47 ` Linus Torvalds
2009-07-23 4:10 ` Linus Torvalds
2009-07-23 5:13 ` Junio C Hamano
2009-07-23 5:17 ` Carlos R. Mafra
2009-07-23 4:40 ` Junio C Hamano
2009-07-23 5:36 ` Linus Torvalds
2009-07-23 5:52 ` Junio C Hamano [this message]
2009-07-23 6:04 ` Junio C Hamano
2009-07-23 17:19 ` Linus Torvalds
2009-07-23 16:07 ` Carlos R. Mafra
2009-07-23 16:19 ` Linus Torvalds
2009-07-23 16:53 ` Carlos R. Mafra
2009-07-23 19:05 ` Linus Torvalds
2009-07-23 19:13 ` Linus Torvalds
2009-07-23 19:55 ` Carlos R. Mafra
2009-07-24 20:36 ` Linus Torvalds
2009-07-24 20:47 ` Linus Torvalds
2009-07-24 21:21 ` Linus Torvalds
2009-07-24 22:13 ` Linus Torvalds
2009-07-24 22:18 ` david
2009-07-24 22:42 ` Linus Torvalds
2009-07-24 22:46 ` david
2009-07-25 2:39 ` Linus Torvalds
2009-07-25 2:53 ` Daniel Barkalow
2009-08-07 4:21 ` Jeff King
2009-07-24 22:54 ` Theodore Tso
2009-07-24 22:59 ` Shawn O. Pearce
2009-07-24 23:28 ` Junio C Hamano
2009-07-26 17:07 ` Avi Kivity
2009-07-26 17:16 ` Johannes Schindelin
2009-07-24 23:46 ` Carlos R. Mafra
2009-07-25 0:41 ` Carlos R. Mafra
2009-07-25 18:04 ` Linus Torvalds
2009-07-25 18:57 ` Timo Hirvonen
2009-07-25 19:06 ` Reece Dunn
2009-07-25 20:31 ` Mike Hommey
2009-07-25 21:02 ` Linus Torvalds
2009-07-25 21:13 ` Linus Torvalds
2009-07-25 23:23 ` Johannes Schindelin
2009-07-26 4:49 ` Linus Torvalds
2009-07-26 16:29 ` Theodore Tso
2009-07-26 7:54 ` Mike Hommey
2009-07-26 10:16 ` Johannes Schindelin
2009-07-26 10:23 ` demerphq
2009-07-26 10:27 ` demerphq
2009-07-25 21:04 ` Carlos R. Mafra
2009-07-23 16:48 ` Anders Kaseorg
2009-07-23 19:03 ` Carlos R. Mafra
2009-07-23 0:23 ` SZEDER Gábor
2009-07-23 2:25 ` Carlos R. Mafra
-- strict thread matches above, loose matches on Subject: below --
2009-07-26 23:21 George Spelvin
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