From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, dstolee@microsoft.com, gitster@pobox.com
Subject: Re: [PATCH v2 2/8] revision: learn '--no-kept-objects'
Date: Wed, 17 Feb 2021 13:35:48 -0500 [thread overview]
Message-ID: <YC1iBEFyQnv2URSV@nand.local> (raw)
In-Reply-To: <YCxSlNK4Ug2exDbv@coredump.intra.peff.net>
On Tue, Feb 16, 2021 at 06:17:40PM -0500, Jeff King wrote:
> On Wed, Feb 03, 2021 at 10:58:57PM -0500, Taylor Blau wrote:
>
> > @@ -3797,6 +3807,11 @@ enum commit_action get_commit_action(struct rev_info *revs, struct commit *commi
> > return commit_ignore;
> > if (revs->unpacked && has_object_pack(&commit->object.oid))
> > return commit_ignore;
> > + if (revs->no_kept_objects) {
> > + if (has_object_kept_pack(&commit->object.oid,
> > + revs->keep_pack_cache_flags))
> > + return commit_ignore;
> > + }
>
> OK, so this has the same "problems" as --unpacked, which is that we can
> miss some objects (i.e., things that are reachable but not-kept may not
> be reported). But it should be OK in this version of the series, because
> we will not be relying on it for selection of objects, but only to fill
> in ordering / namehash fields.
>
> Should we warn people about that, either as a comment or in the commit
> message?
Yeah, let's warn about it in the commit message. We could put it in the
documentation, but...
> > +--no-kept-objects[=<kind>]::
> > + Halts the traversal as soon as an object in a kept pack is
> > + found. If `<kind>` is `on-disk`, only packs with a corresponding
> > + `*.keep` file are ignored. If `<kind>` is `in-core`, only packs
> > + with their in-core kept state set are ignored. Otherwise, both
> > + kinds of kept packs are ignored.
>
> Likewise, I wonder whether we need to expose this mode to users.
> Normally I'm a fan of doing so, because it allows scripted callers
> access to more of the internals, but:
>
> - the semantics are kind of weird about where we draw the line between
> performance and absolute correctness
>
> - the "in-core" thing is a bit weird for callers of rev-list; how do I
> as a caller mark a pack as kept-in-core? I think it's only an
> internal pack-objects thing.
>
> Once we support this in rev-list, we'll have to do it forever (or deal
> with deprecation, etc). If we just need it internally, maybe it's wise
> to leave it as a something you ask for by manipulating rev_info
> directly. Or perhaps leave it as an undocumented interface we use for
> testing, and not something we promise to keep working.
I think that you raise a good point about not advertising this option,
since doing so paints us into a corner that we have to keep it working
and behaving consistently forever.
I'm not opposed to the idea that we may eventually want to do so, but I
think that this is too early for that. As you note, we *could* just
expose it in rev_info flags, but that makes it much more difficult to
test some of the tricky cases that are added in t6114, so I think a
middle ground of having an undocumented option satisfies both of our
wants.
> > --- a/list-objects.c
> > +++ b/list-objects.c
> > @@ -338,6 +338,13 @@ static void traverse_trees_and_blobs(struct traversal_context *ctx,
> > ctx->show_object(obj, name, ctx->show_data);
> > continue;
> > }
> > + if (ctx->revs->no_kept_objects) {
> > + struct pack_entry e;
> > + if (find_kept_pack_entry(ctx->revs->repo, &obj->oid,
> > + ctx->revs->keep_pack_cache_flags,
> > + &e))
> > + continue;
> > + }
>
> This hunk is interesting.
>
> There is no similar check for revs->unpacked in list-objects.c to cut
> off the traversal. And indeed, running "rev-list --unpacked" will
> generally look at the _whole_ tree for a commit that is unpacked, even
> if all of the tree entries are packed. That's something we might
> consider changing in the name of performance (though it does increase
> the number of cases where --unpacked will fail to find an unpacked but
> reachable object).
>
> But this is a funny place to put it. If I understand it correctly, it is
> cutting off the traversal at the very top of the tree. I.e., if we had a
> commit that is not-kept, we'd queue it's root tree. And then we might
> find that the root tree is kept, and avoid traversing it. But if we _do_
> traverse it, we would look at every subtree it contains, even if they
> are kept! That's because we recurse the tree via the recursive
> process_tree(), not by queueing more objects in the pending array here.
>
> So this check seems to exist in a funny middle ground. I think it's
> unlikely to catch anything useful (usually commits have a unique root
> tree; it's all of the untouched parts of the subtrees that will be in
> the kept packs). IMHO we should either drop it (and act like
> "--unpacked", accepting that we may traverse some extra tree objects),
> or we should go all-in on performance and cut it off in the top of
> process_tree().
Agreed. Let's drop it.
> -Peff
Thanks,
Taylor
next prev parent reply other threads:[~2021-02-17 18:39 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 23:23 [PATCH 00/10] repack: support repacking into a geometric sequence Taylor Blau
2021-01-19 23:24 ` [PATCH 01/10] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-01-20 13:40 ` Derrick Stolee
2021-01-20 14:38 ` Taylor Blau
2021-01-29 2:33 ` Junio C Hamano
2021-01-29 18:38 ` Taylor Blau
2021-01-29 19:31 ` Jeff King
2021-01-29 20:20 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 02/10] revision: learn '--no-kept-objects' Taylor Blau
2021-01-29 3:10 ` Junio C Hamano
2021-01-29 19:13 ` Taylor Blau
2021-01-19 23:24 ` [PATCH 03/10] builtin/pack-objects.c: learn '--assume-kept-packs-closed' Taylor Blau
2021-01-29 3:21 ` Junio C Hamano
2021-01-29 19:19 ` Jeff King
2021-01-29 20:01 ` Taylor Blau
2021-01-29 20:25 ` Jeff King
2021-01-29 22:10 ` Taylor Blau
2021-01-29 22:57 ` Jeff King
2021-01-29 23:03 ` Junio C Hamano
2021-01-29 23:28 ` Taylor Blau
2021-02-02 3:04 ` Taylor Blau
2021-01-29 23:31 ` Jeff King
2021-01-29 22:13 ` Junio C Hamano
2021-01-29 20:30 ` Junio C Hamano
2021-01-29 22:43 ` Jeff King
2021-01-29 22:53 ` Taylor Blau
2021-01-29 23:00 ` Jeff King
2021-01-29 23:10 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 04/10] p5303: add missing &&-chains Taylor Blau
2021-01-19 23:24 ` [PATCH 05/10] p5303: measure time to repack with keep Taylor Blau
2021-01-29 3:40 ` Junio C Hamano
2021-01-29 19:32 ` Jeff King
2021-01-29 20:04 ` [PATCH] p5303: avoid sed GNU-ism Jeff King
2021-01-29 20:19 ` Eric Sunshine
2021-01-29 20:27 ` Jeff King
2021-01-29 20:36 ` Eric Sunshine
2021-01-29 22:11 ` Taylor Blau
2021-01-29 20:38 ` [PATCH 05/10] p5303: measure time to repack with keep Junio C Hamano
2021-01-29 22:10 ` Jeff King
2021-01-29 23:12 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 06/10] pack-objects: rewrite honor-pack-keep logic Taylor Blau
2021-01-19 23:24 ` [PATCH 07/10] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-01-19 23:24 ` [PATCH 08/10] builtin/pack-objects.c: teach '--keep-pack-stdin' Taylor Blau
2021-01-19 23:24 ` [PATCH 09/10] builtin/repack.c: extract loose object handling Taylor Blau
2021-01-20 13:59 ` Derrick Stolee
2021-01-20 14:34 ` Taylor Blau
2021-01-20 15:51 ` Derrick Stolee
2021-01-21 3:45 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 10/10] builtin/repack.c: add '--geometric' option Taylor Blau
2021-01-20 14:05 ` [PATCH 00/10] repack: support repacking into a geometric sequence Derrick Stolee
2021-02-04 3:58 ` [PATCH v2 0/8] " Taylor Blau
2021-02-04 3:58 ` [PATCH v2 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-16 21:42 ` Jeff King
2021-02-16 21:48 ` Taylor Blau
2021-02-04 3:58 ` [PATCH v2 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-16 23:17 ` Jeff King
2021-02-17 18:35 ` Taylor Blau [this message]
2021-02-04 3:59 ` [PATCH v2 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-16 23:46 ` Jeff King
2021-02-17 18:59 ` Taylor Blau
2021-02-17 19:21 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-04 3:59 ` [PATCH v2 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-16 23:58 ` Jeff King
2021-02-17 0:02 ` Jeff King
2021-02-17 19:13 ` Taylor Blau
2021-02-17 19:25 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-17 16:05 ` Jeff King
2021-02-17 19:23 ` Taylor Blau
2021-02-17 19:29 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-17 17:11 ` Jeff King
2021-02-17 19:54 ` Taylor Blau
2021-02-17 20:25 ` Jeff King
2021-02-17 20:29 ` Taylor Blau
2021-02-17 21:43 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-17 18:17 ` Jeff King
2021-02-17 20:01 ` Taylor Blau
2021-02-17 0:01 ` [PATCH v2 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-17 18:18 ` Jeff King
2021-02-18 3:14 ` [PATCH v3 " Taylor Blau
2021-02-18 3:14 ` [PATCH v3 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-18 3:14 ` [PATCH v3 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-18 3:14 ` [PATCH v3 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-18 3:14 ` [PATCH v3 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-18 3:14 ` [PATCH v3 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-18 3:14 ` [PATCH v3 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-18 3:14 ` [PATCH v3 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-18 3:14 ` [PATCH v3 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-23 0:31 ` [PATCH v3 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-23 1:06 ` Taylor Blau
2021-02-23 1:42 ` Jeff King
2021-02-23 2:24 ` [PATCH v4 " Taylor Blau
2021-02-23 2:25 ` [PATCH v4 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-23 2:25 ` [PATCH v4 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-23 2:25 ` [PATCH v4 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-23 8:07 ` Junio C Hamano
2021-02-23 18:51 ` Jeff King
2021-02-23 2:25 ` [PATCH v4 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-23 2:25 ` [PATCH v4 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-23 2:25 ` [PATCH v4 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-23 2:25 ` [PATCH v4 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-23 2:25 ` [PATCH v4 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-24 23:19 ` Junio C Hamano
2021-02-24 23:43 ` Junio C Hamano
2021-03-04 21:40 ` Taylor Blau
2021-03-04 21:55 ` Taylor Blau
2021-02-23 3:39 ` [PATCH v4 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-23 7:43 ` Junio C Hamano
2021-02-23 18:44 ` Jeff King
2021-02-23 19:54 ` Martin Fick
2021-02-23 20:06 ` Taylor Blau
2021-02-23 21:57 ` Martin Fick
2021-02-23 20:15 ` Jeff King
2021-02-23 21:41 ` Martin Fick
2021-02-23 21:53 ` Jeff King
2021-02-24 18:13 ` Martin Fick
2021-02-26 6:23 ` Jeff King
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