From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Stefan Beller <sbeller@google.com>,
git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: [PATCH 0/4] un-breaking pack-objects with bitmaps
Date: Sat, 1 Sep 2018 03:41:45 -0400 [thread overview]
Message-ID: <20180901074145.GA24023@sigill.intra.peff.net> (raw)
In-Reply-To: <20180831225558.GA22917@sigill.intra.peff.net>
On Fri, Aug 31, 2018 at 06:55:58PM -0400, Jeff King wrote:
> On Fri, Aug 31, 2018 at 05:23:17PM +0200, Ævar Arnfjörð Bjarmason wrote:
>
> > On Tue, Aug 21 2018, Jeff King wrote:
> >
> > > +int bitmap_has_sha1_in_uninteresting(struct bitmap_index *bitmap_git,
> > > + const unsigned char *sha1)
> > > +{
> > > + int pos;
> > > +
> > > + if (!bitmap_git)
> > > + return 0; /* no bitmap loaded */
> > > + if (!bitmap_git->result)
> > > + BUG("failed to perform bitmap walk before querying");
> >
> > Some part of what calls this completely breaks pushing from the "next"
> > branch when you have local bitmaps (we *really* should have some tests
> > for this...).
>
> Yikes, thanks for reporting. I agree we need better tests here.
OK, here is the fix. Since the problem is in 'next', this is done as a
patch on top of jk/pack-delta-reuse-with-bitmap. But since we're set to
rewind 'next' post-release anyway, we could squash it directly into
30cdc33fba from the original series. That would help later bisections
from running into it, which may be worth it as it's a pretty severe
breakage. Or maybe not:
1. The test suite doesn't actually fail, because it's toy repos are
too small.
2. It only triggers in the real-world if you have bitmaps turned on,
which are not the default.
So it may not be that likely in practice to bother a hypothetical future
bisecting developer.
> [1] Actually, there is also prepare_bitmap_git(), but it is not really
> for general use by callers. It should be made static, or better yet,
> I suspect it can be folded into its callers.
This actually turned out not to work. There's a caller over in
pack-bitmap-write.c, and it makes things worse to try to expand the
logic there. So it technically _is_ possible to have a bitmap_index
without a "have" field, but it also doesn't make sense to ask about
"uninteresting" objects there. You haven't done (and cannot do) a
traversal on such an object.
Which I think goes back to Stefan's original question: is this just a
crappy API? And the answer is "yes, to some degree". There are really
two uses of bitmaps:
- you want to do a traverse_commit_list() walk, but faster
- you want to selectively query the on-disk bitmaps (e.g., you are
walking for --contains and want to ask "do we have a bitmap for this
object?"
Those currently use the same struct bitmap_index, but with two different
constructors (prepare_bitmap_git and prepare_bitmap_walk). It probably
ought to be two different ones (with the "walk" variant using the
"query" variant under the hood). I've punted on that full conversion for
now, but did clean up a few confusing bits.
[1/4]: bitmap_has_sha1_in_uninteresting(): drop BUG check
The actual fix. This should get merged to next ASAP (or the original
topic just reverted).
[2/4]: t5310: test delta reuse with bitmaps
I did this separately to give us flexibility to squash or merge
quickly. But it does find Ævar's bug on a git without patch 1.
[3/4]: traverse_bitmap_commit_list(): don't free result
The original assert should have simply been useless, but it was the
surprising behavior of this function that turned it into a bug.
[4/4]: pack-bitmap: drop "loaded" flag
And this is just an annoyance I ran into, which is a fallout from
our conversion to using an allocated bitmap_index struct.
pack-bitmap.c | 14 ++-----
pack-bitmap.h | 2 +-
t/t5310-pack-bitmaps.sh | 93 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 97 insertions(+), 12 deletions(-)
-Peff
next prev parent reply other threads:[~2018-09-01 7:41 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-21 18:41 [PATCH] test-tool.h: include git-compat-util.h Jeff King
2018-08-21 19:03 ` Junio C Hamano
2018-08-21 19:06 ` [PATCH 1/6] t/perf: factor boilerplate out of test_perf Jeff King
2018-08-21 19:06 ` [PATCH 2/6] t/perf: factor out percent calculations Jeff King
2018-08-21 19:06 ` [PATCH 3/6] t/perf: add infrastructure for measuring sizes Jeff King
2018-08-22 13:40 ` Derrick Stolee
2018-08-22 15:31 ` Jeff King
2018-08-21 19:06 ` [PATCH 4/6] t/perf: add perf tests for fetches from a bitmapped server Jeff King
2018-08-21 19:07 ` [PATCH 5/6] pack-bitmap: save "have" bitmap from walk Jeff King
2018-08-21 19:47 ` Derrick Stolee
2018-08-21 19:54 ` Jeff King
2018-08-31 15:23 ` Ævar Arnfjörð Bjarmason
2018-08-31 22:55 ` Jeff King
2018-09-01 7:41 ` Jeff King [this message]
2018-09-01 7:44 ` [PATCH 1/4] bitmap_has_sha1_in_uninteresting(): drop BUG check Jeff King
2018-09-01 7:48 ` [PATCH 2/4] t5310: test delta reuse with bitmaps Jeff King
2018-09-01 8:03 ` Jeff King
2018-09-01 20:29 ` Ævar Arnfjörð Bjarmason
2018-09-01 22:46 ` Ben Peart
2018-09-02 5:51 ` Jeff King
2018-09-04 19:05 ` Stefan Beller
2018-09-04 19:45 ` Junio C Hamano
2018-09-04 20:02 ` Jeff King
2018-09-01 7:49 ` [PATCH 3/4] traverse_bitmap_commit_list(): don't free result Jeff King
2018-09-01 7:50 ` [PATCH 4/4] pack-bitmap: drop "loaded" flag Jeff King
2018-09-04 19:30 ` [PATCH 0/4] un-breaking pack-objects with bitmaps Stefan Beller
2018-09-04 20:03 ` Jeff King
2018-09-08 6:43 ` Ævar Arnfjörð Bjarmason
2018-09-10 16:53 ` Junio C Hamano
2018-09-10 18:48 ` Jeff King
2018-09-10 19:23 ` Junio C Hamano
2018-08-21 19:07 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King
2018-08-21 19:43 ` Junio C Hamano
2018-08-21 19:50 ` Junio C Hamano
2018-08-21 20:07 ` Jeff King
2018-08-21 20:14 ` Jeff King
2018-08-21 20:52 ` Junio C Hamano
2018-08-21 21:30 ` Jeff King
2018-08-21 20:57 ` Junio C Hamano
2018-08-21 21:32 ` Jeff King
2018-08-23 0:43 ` [PATCH 0/9] trailer-parsing false positives Jeff King
2018-08-23 0:44 ` [PATCH 1/9] trailer: use size_t for string offsets Jeff King
2018-08-23 0:45 ` [PATCH 2/9] trailer: use size_t for iterating trailer list Jeff King
2018-08-23 0:46 ` [PATCH 3/9] trailer: pass process_trailer_opts to trailer_info_get() Jeff King
2018-08-23 0:48 ` [PATCH 4/9] interpret-trailers: tighten check for "---" patch boundary Jeff King
2018-08-23 0:49 ` [PATCH 5/9] interpret-trailers: allow suppressing "---" divider Jeff King
2018-08-23 0:50 ` [PATCH 6/9] pretty, ref-filter: format %(trailers) with no_divider option Jeff King
2018-08-23 0:50 ` [PATCH 7/9] sequencer: ignore "---" divider when parsing trailers Jeff King
2018-08-23 0:50 ` [PATCH 8/9] append_signoff: use size_t for string offsets Jeff King
2018-08-23 0:51 ` [PATCH 9/9] sequencer: handle ignore_footer when parsing trailers Jeff King
2018-08-23 18:30 ` [PATCH 0/9] trailer-parsing false positives Junio C Hamano
2018-08-24 7:26 ` Jeff King
2018-08-21 20:00 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King
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