From: Jeff King <peff@peff.net>
To: Derrick Stolee <stolee@gmail.com>
Cc: Christian Couder <chriscool@tuxfamily.org>,
"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: Git Test Coverage Report (v2.20.0-rc0)
Date: Tue, 20 Nov 2018 06:34:23 -0500 [thread overview]
Message-ID: <20181120113423.GA29319@sigill.intra.peff.net> (raw)
In-Reply-To: <6f532502-d4b6-17f6-0ec7-01079077ac90@gmail.com>
On Mon, Nov 19, 2018 at 10:40:53AM -0500, Derrick Stolee wrote:
> > 28b8a73080 builtin/pack-objects.c 2793) depth++;
> > 108f530385 builtin/pack-objects.c 2797) oe_set_tree_depth(&to_pack, ent,
> > depth);
>
> This 'depth' variable is incremented as part of a for loop in this patch:
>
> static void show_object(struct object *obj, const char *name, void *data)
> @@ -2686,6 +2706,19 @@ static void show_object(struct object *obj, const
> char *name, void *data)
> add_preferred_base_object(name);
> add_object_entry(&obj->oid, obj->type, name, 0);
> obj->flags |= OBJECT_ADDED;
> +
> + if (use_delta_islands) {
> + const char *p;
> + unsigned depth = 0;
> + struct object_entry *ent;
> +
> + for (p = strchr(name, '/'); p; p = strchr(p + 1, '/'))
> + depth++;
> +
> + ent = packlist_find(&to_pack, obj->oid.hash, NULL);
> + if (ent && depth > ent->tree_depth)
> + ent->tree_depth = depth;
> + }
> }
>
> And that 'ent->tree_depth = depth;' line is replaced with the
> oe_set_tree_depth() call in the report.
>
> Since depth is never incremented, we are not covering this block. Is it
> possible to test?
This should be covered by the fix in:
https://public-inbox.org/git/20181120095053.GC22742@sigill.intra.peff.net/
because now entries at the top-level are depth "1". The "depth++" line
is still never executed in our test suite. I'm not sure how much that
matters.
> > delta-islands.c
> > c8d521faf7 53) memcpy(b, old, size);
>
> This memcpy happens when the 'old' island_bitmap is passed to
> island_bitmap_new(), but...
>
> > c8d521faf7 187) b->refcount--;
> > c8d521faf7 188) b = kh_value(island_marks, pos) = island_bitmap_new(b);
>
> This block has the only non-NULL caller to island_bitmap_new().
This is another case where it triggers a lot for a reasonably-sized
repo, but it's hard to construct a small case. This code implements a
copy-on-write of the bitmap, which means the same objects have to be
accessible from two different paths through the reachability graph, each
with different island marks. And then a test would I guess make sure
that the correct subsets of objects never become deltas, which gets
complicated.
And I think that's a pattern with the delta-island code. What we really
care about most is that if we throw a real fork-network repository at
it, it produces faster clones with fewer un-reusable deltas. So I think
a much more interesting approach here would be perf tests. But:
- we'd want to count those as coverage, and that likely makes your
coverage tests prohibitively expensive
- it requires a specialized repo to demonstrate, which most people
aren't going to have handy
> > c8d521faf7 212) obj = ((struct tag *)obj)->tagged;
> > c8d521faf7 213) if (obj) {
> > c8d521faf7 214) parse_object(the_repository, &obj->oid);
> > c8d521faf7 215) marks = create_or_get_island_marks(obj);
> > c8d521faf7 216) island_bitmap_set(marks, island_counter);
>
> It appears that this block would happen if we placed a tag in the delta
> island.
Yep. Again, exercised by real repositories.
I'm not sure how far we want to go in the blind pursuit of coverage.
Certainly we could add a tag to the repo in t5320, and this code would
get executed. But verifying that it's doing the right thing is much
harder (and is more easily done with a perf test).
> > c8d521faf7 397) strbuf_addch(&island_name, '-');
>
> This block is inside the following patch:
> [...]
Yeah, this triggers if your regex has more than one capture group (and
likewise, we almost certainly don't run the "you have too many groups"
warning).
> > c8d521faf7 433) continue;
> > c8d521faf7 436) list[dst] = list[src];
>
> These blocks are inside the following nested loop in deduplicate_islands():
>
> + for (ref = 0; ref + 1 < island_count; ref++) {
> + for (src = ref + 1, dst = src; src < island_count; src++) {
> + if (list[ref]->hash == list[src]->hash)
> + continue;
> +
> + if (src != dst)
> + list[dst] = list[src];
> +
> + dst++;
> + }
> + island_count = dst;
> + }
>
> This means that our "deduplication" logic is never actually doing anything
> meaningful.
Sorry, I don't even remember what this code is trying to do. The island
code is 5+ years old, and just recently ported to upstream Git by
Christian. And that's perhaps part of my laziness in the above tests; it
would be a significant effort to re-figure out all these corner cases.
It's a big part of why I hadn't been sending the patches upstream
myself.
-Peff
next prev parent reply other threads:[~2018-11-20 11:34 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-19 2:54 Git Test Coverage Report (v2.20.0-rc0) Derrick Stolee
2018-11-19 15:40 ` Derrick Stolee
2018-11-19 16:21 ` Jeff King
2018-11-19 18:44 ` Jeff King
2018-11-19 19:00 ` Ben Peart
2018-11-19 21:06 ` Derrick Stolee
2018-11-20 11:34 ` Jeff King [this message]
2018-11-20 12:17 ` Derrick Stolee
2018-11-20 12:40 ` Jeff King
2018-11-19 18:33 ` Ævar Arnfjörð Bjarmason
2018-11-19 18:51 ` [PATCH] tests: add a special setup where rebase.useBuiltin is off (Re: Git Test Coverage Report (v2.20.0-rc0)) Jonathan Nieder
2018-11-19 21:03 ` Ævar Arnfjörð Bjarmason
2018-11-19 19:10 ` Git Test Coverage Report (v2.20.0-rc0) Derrick Stolee
2018-11-19 19:39 ` Ævar Arnfjörð Bjarmason
2018-11-19 19:44 ` Derrick Stolee
2018-11-19 21:31 ` Derrick Stolee
2018-11-20 20:43 ` Johannes Schindelin
-- strict thread matches above, loose matches on Subject: below --
2018-11-21 15:20 [ANNOUNCE] Git v2.20.0-rc1 Junio C Hamano
2018-11-22 15:58 ` Ævar Arnfjörð Bjarmason
2018-11-22 19:27 ` Eric Sunshine
2018-11-22 21:12 ` [PATCH 0/2] format-patch: pre-2.20 range-diff regression fix Ævar Arnfjörð Bjarmason
2018-11-22 21:12 ` [PATCH 1/2] format-patch: add a more exhaustive --range-diff test Ævar Arnfjörð Bjarmason
2018-11-24 4:14 ` Junio C Hamano
2018-11-24 11:45 ` Ævar Arnfjörð Bjarmason
2018-11-22 21:12 ` [PATCH 2/2] format-patch: don't include --stat with --range-diff output Ævar Arnfjörð Bjarmason
2018-11-24 2:26 ` Junio C Hamano
2018-11-24 4:17 ` Junio C Hamano
2018-11-28 20:18 ` [PATCH 0/2] format-patch: fix root cause of recent regression Ævar Arnfjörð Bjarmason
2018-11-28 20:18 ` [PATCH 1/2] format-patch: add test for --range-diff diff output Ævar Arnfjörð Bjarmason
2018-11-28 20:18 ` [PATCH 2/2] format-patch: allow for independent diff & range-diff options Ævar Arnfjörð Bjarmason
2018-11-29 2:59 ` Junio C Hamano
2018-11-29 10:07 ` Johannes Schindelin
2018-11-29 10:30 ` Ævar Arnfjörð Bjarmason
2018-11-29 12:12 ` Johannes Schindelin
2018-11-29 14:35 ` Ævar Arnfjörð Bjarmason
2018-11-29 15:41 ` Johannes Schindelin
2018-11-29 16:03 ` Ævar Arnfjörð Bjarmason
2018-11-29 19:03 ` Johannes Schindelin
2018-11-30 2:30 ` Junio C Hamano
2018-11-30 4:27 ` [PATCH] format-patch: do not let its diff-options affect --range-diff (was Re: [PATCH 2/2] format-patch: allow for independent diff & range-diff options) Junio C Hamano
2018-11-30 8:57 ` Junio C Hamano
2018-11-30 9:24 ` Ævar Arnfjörð Bjarmason
2018-11-30 12:32 ` Johannes Schindelin
2018-11-30 9:31 ` Eric Sunshine
2018-12-03 13:27 ` Martin Ågren
2018-12-03 20:07 ` [PATCH v2] range-diff: always pass at least minimal diff options Martin Ågren
2018-12-03 21:21 ` [PATCH v3] " Eric Sunshine
2018-12-04 1:35 ` Junio C Hamano
2018-12-04 5:40 ` Martin Ågren
2018-11-30 9:58 ` [PATCH 2/2] format-patch: allow for independent diff & range-diff options Eric Sunshine
2018-11-26 7:35 ` [ANNOUNCE] Git v2.20.0-rc1 Junio C Hamano
2018-11-26 15:41 ` Elijah Newren
2018-11-27 0:40 ` Junio C Hamano
2018-11-13 12:38 [PATCH 0/1] rebase: understand -C again, refactor Johannes Schindelin via GitGitGadget
2018-11-13 12:38 ` [PATCH 1/1] rebase: really just passthru the `git am` options Johannes Schindelin via GitGitGadget
2018-11-13 13:05 ` Junio C Hamano
2018-11-13 15:05 ` Phillip Wood
2018-11-13 19:21 ` Johannes Schindelin
2018-11-13 19:58 ` Phillip Wood
2018-11-13 21:50 ` rebase-in-C stability for 2.20 Ævar Arnfjörð Bjarmason
2018-11-14 0:07 ` Stefan Beller
2018-11-14 9:01 ` [PATCH 0/2] rebase.useBuiltin doc & test mode Ævar Arnfjörð Bjarmason
2018-11-14 14:07 ` Johannes Schindelin
2018-11-14 9:01 ` [PATCH 1/2] rebase doc: document rebase.useBuiltin Ævar Arnfjörð Bjarmason
2018-11-14 9:01 ` [PATCH 2/2] tests: add a special setup where rebase.useBuiltin is off Ævar Arnfjörð Bjarmason
2018-11-14 0:36 ` rebase-in-C stability for 2.20 Elijah Newren
2018-11-14 3:39 ` Junio C Hamano
2018-11-24 20:54 ` [ANNOUNCE] Git v2.20.0-rc1 Ævar Arnfjörð Bjarmason
2018-11-25 1:00 ` Junio C Hamano
2018-11-26 6:10 ` [PATCH] rebase: mark the C reimplementation as an experimental opt-in feature (was Re: [ANNOUNCE] Git v2.20.0-rc1) Junio C Hamano
2018-11-28 4:31 ` Jonathan Nieder
2018-11-28 9:23 ` Johannes Schindelin
2018-11-28 12:21 ` Ævar Arnfjörð Bjarmason
2018-11-29 4:58 ` Junio C Hamano
2018-11-29 14:17 ` Johannes Schindelin
2018-11-29 14:30 ` Ian Jackson
2018-11-29 15:39 ` Johannes Schindelin
2018-11-29 15:50 ` Ian Jackson
2018-11-29 16:14 ` Johannes Schindelin
2018-11-29 16:26 ` Ian Jackson
2018-11-26 22:52 ` [ANNOUNCE] Git v2.20.0-rc1 Johannes Schindelin
2018-11-26 23:47 ` Johannes Schindelin
2018-11-28 4:07 ` Junio C Hamano
2018-11-28 9:30 ` Johannes Schindelin
2018-11-14 14:22 ` [PATCH 1/1] rebase: really just passthru the `git am` options Johannes Schindelin
2018-11-14 7:29 ` [PATCH 0/1] rebase: understand -C again, refactor Jeff King
2018-11-14 14:28 ` Johannes Schindelin
2018-11-14 16:25 ` [PATCH v2 0/2] " Johannes Schindelin via GitGitGadget
2018-11-14 16:25 ` [PATCH v2 1/2] rebase: really just passthru the `git am` options Johannes Schindelin via GitGitGadget
2018-11-14 16:25 ` [PATCH v2 2/2] rebase: validate -C<n> and --whitespace=<mode> parameters early Johannes Schindelin via GitGitGadget
2018-11-14 16:37 ` Phillip Wood
2018-11-14 21:24 ` Johannes Schindelin
2018-11-19 12:38 ` Ævar Arnfjörð Bjarmason
2018-11-19 21:37 ` Git Test Coverage Report (v2.20.0-rc0) Ævar Arnfjörð Bjarmason
2018-11-20 10:58 ` [PATCH v2 2/2] rebase: validate -C<n> and --whitespace=<mode> parameters early Johannes Schindelin
2018-11-20 11:42 ` [PATCH] rebase: mark a test as failing with rebase.useBuiltin=false Ævar Arnfjörð Bjarmason
2018-11-20 19:55 ` Johannes Schindelin
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