From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Jonathan Tan <jonathantanmy@google.com>,
rafaeloliveira.cs@gmail.com, git@vger.kernel.org,
szeder.dev@gmail.com
Subject: Re: [PATCH 2/2] repack: avoid loosening promisor pack objects in partial clones
Date: Thu, 15 Apr 2021 05:03:08 -0400 [thread overview]
Message-ID: <YHgBTPGTmDUBMGA9@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqqo8egurx5.fsf@gitster.g>
On Wed, Apr 14, 2021 at 08:51:02PM -0700, Junio C Hamano wrote:
> Jonathan Tan <jonathantanmy@google.com> writes:
>
> >> When `-A` and `-d` are used together, besides packing all objects (-A)
> >> and removing redundant packs (-d), it also unpack all unreachable
> >> objects and deletes them by calling `git pruned-packed`.
> >
> > I still think of these objects as not unreachable, even though I know
> > that pack-objects calls them that (the argument is called
> > --unpack-unreachable). So I would say "it also loosens all objects that
> > were previously packed but did not go into the new pack", but perhaps
> > this is OK too.
>
> Hmph, that is puzzling. I understand that the operation about
>
> (1) finding all the objects that are still reachable and send them
> into a newly created pack, and
>
> (2) among the objects that were previously in the packs, eject
> those that weren't made into the new pack with the previous
> point.
>
> Where did I get it wrong? If all the reachable ones are dealt with
> with the first point, what is leftover is not reachable, no?
Right. I think your understanding is correct, and the commit message is
a bit confused. Normally after we eject loose objects, they'd stay there
(a follow-up git-gc may run git-prune and delete them, though if they
were recent enough not to just drop completely during the repack, then
git-prune would likewise leave them be). Talking about prune-packed here
is misleading, because it usually has nothing to do with these objects.
What makes the partial-clone situation under discussion interesting is
that the objects _are_ reachable. They are excluded from the new pack
because we put them in a separate promisor pack. But we erroneously turn
them loose, rather than realizing that they were excluded for a
different reason.
So the fundamental bug is that we turn them loose at all. What makes the
bug trickier to see is that when we run prune-packed afterwards, we then
clean up the evidence of the bug (so it looks more like a performance
problem than a correctness one).
-Peff
next prev parent reply other threads:[~2021-04-15 9:03 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 9:04 rather slow 'git repack' in 'blob:none' partial clones SZEDER Gábor
2021-04-05 1:02 ` Rafael Silva
2021-04-07 21:17 ` Jeff King
2021-04-08 0:02 ` Jonathan Tan
2021-04-08 0:35 ` Jeff King
2021-04-12 7:09 ` Rafael Silva
2021-04-12 21:36 ` SZEDER Gábor
2021-04-12 21:49 ` Bryan Turner
2021-04-12 23:51 ` Jeff King
2021-04-12 23:47 ` Jeff King
2021-04-13 7:12 ` [PATCH 0/3] low-hanging performance fruit with promisor packs Jeff King
2021-04-13 7:15 ` [PATCH 1/3] is_promisor_object(): free tree buffer after parsing Jeff King
2021-04-13 20:17 ` Junio C Hamano
2021-04-14 5:18 ` Jeff King
2021-04-13 7:16 ` [PATCH 2/3] lookup_unknown_object(): take a repository argument Jeff King
2021-04-13 7:17 ` [PATCH 3/3] revision: avoid parsing with --exclude-promisor-objects Jeff King
2021-04-13 20:22 ` Junio C Hamano
2021-04-13 18:10 ` [PATCH 0/3] low-hanging performance fruit with promisor packs SZEDER Gábor
2021-04-14 17:14 ` Jonathan Tan
2021-04-14 19:22 ` Rafael Silva
2021-04-13 18:05 ` rather slow 'git repack' in 'blob:none' partial clones SZEDER Gábor
2021-04-14 5:14 ` Jeff King
2021-04-11 10:59 ` SZEDER Gábor
2021-04-12 7:53 ` Rafael Silva
2021-04-14 19:14 ` [PATCH 0/2] prevent `repack` to unpack and delete promisor objects Rafael Silva
2021-04-14 19:14 ` [PATCH 1/2] repack: teach --no-prune-packed to skip `git prune-packed` Rafael Silva
2021-04-14 23:50 ` Jonathan Tan
2021-04-18 14:15 ` Rafael Silva
2021-04-14 19:14 ` [PATCH 2/2] repack: avoid loosening promisor pack objects in partial clones Rafael Silva
2021-04-15 1:04 ` Jonathan Tan
2021-04-15 3:51 ` Junio C Hamano
2021-04-15 9:03 ` Jeff King [this message]
2021-04-15 9:05 ` Jeff King
2021-04-18 7:12 ` Rafael Silva
2021-04-15 18:06 ` Junio C Hamano
2021-04-18 8:40 ` Rafael Silva
2021-04-14 22:10 ` [PATCH 0/2] prevent `repack` to unpack and delete promisor objects Junio C Hamano
2021-04-15 9:15 ` Jeff King
2021-04-18 8:20 ` Rafael Silva
2021-04-18 13:57 ` [PATCH v2 0/1] " Rafael Silva
2021-04-18 13:57 ` [PATCH v2 1/1] repack: avoid loosening promisor objects in partial clones Rafael Silva
2021-04-19 19:15 ` Jonathan Tan
2021-04-21 18:54 ` Rafael Silva
2021-04-19 23:09 ` Junio C Hamano
2021-04-21 19:25 ` Rafael Silva
2021-04-21 19:32 ` [PATCH v3] " Rafael Silva
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