We're recomputing the prefix length on every iteration of the ref
iterator. Precompute it for another speedup when iterating over 1
million refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 100.3 ms ± 3.7 ms [User: 97.3 ms, System: 2.8 ms]
Range (min … max): 97.5 ms … 139.7 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 95.8 ms ± 3.4 ms [User: 92.9 ms, System: 2.8 ms]
Range (min … max): 93.0 ms … 121.9 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.05 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We have a few functions which are basically just accessors to
structures. As those functions are executed inside the hot loop when
iterating through many refs, the fact that they cannot be inlined is
costing us some performance.
Move the function definitions into their respective headers so that they
can be inlined. This results in a performance improvement when iterating
over 1 million refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 105.9 ms ± 3.6 ms [User: 103.0 ms, System: 2.8 ms]
Range (min … max): 103.1 ms … 133.4 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 100.7 ms ± 3.4 ms [User: 97.8 ms, System: 2.8 ms]
Range (min … max): 97.8 ms … 124.0 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.05 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When reading a record from a block, we need to decode the record's key.
As reftable keys are prefix-compressed, meaning they reuse a prefix from
the preceding record's key, this is a bit more involved than just having
to copy the relevant bytes: we need to figure out the prefix and suffix
lengths, copy the prefix from the preceding record and finally copy the
suffix from the current record.
This is done by passing three buffers to `reftable_decode_key()`: one
buffer that holds the result, one buffer that holds the last key, and
one buffer that points to the current record. The final key is then
assembled by calling `strbuf_add()` twice to copy over the prefix and
suffix.
Performing two memory copies is inefficient though. And we can indeed do
better by decoding keys in place. Instead of providing two buffers, the
caller may only call a single buffer that is already pre-populated with
the last key. Like this, we only have to call `strbuf_setlen()` to trim
the record to its prefix and then `strbuf_add()` to add the suffix.
This refactoring leads to a noticeable performance bump when iterating
over 1 million refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 112.2 ms ± 3.9 ms [User: 109.3 ms, System: 2.8 ms]
Range (min … max): 109.2 ms … 149.6 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 106.0 ms ± 3.5 ms [User: 103.2 ms, System: 2.7 ms]
Range (min … max): 103.2 ms … 133.7 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.06 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Do the same optimization as in the preceding commit, but this time for
`reftable_record_copy()`. While not as noticeable, it still results in a
small speedup when iterating over 1 million refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 114.0 ms ± 3.8 ms [User: 111.1 ms, System: 2.7 ms]
Range (min … max): 110.9 ms … 144.3 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 112.5 ms ± 3.7 ms [User: 109.5 ms, System: 2.8 ms]
Range (min … max): 109.2 ms … 140.7 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.01 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When decoding a reftable record we will first release the user-provided
record and then decode the new record into it. This is quite inefficient
as we basically need to reallocate at least the refname every time.
Refactor the function to start tracking the refname capacity. Like this,
we can stow away the refname, release, restore and then grow the refname
to the required number of bytes via `REFTABLE_ALLOC_GROW()`.
This refactoring is safe to do because all functions that assigning to
the refname will first call `reftable_ref_record_release()`, which will
zero out the complete record after releasing memory.
This change results in a nice speedup when iterating over 1 million
refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 124.0 ms ± 3.9 ms [User: 121.1 ms, System: 2.7 ms]
Range (min … max): 120.4 ms … 152.7 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 114.4 ms ± 3.7 ms [User: 111.5 ms, System: 2.7 ms]
Range (min … max): 111.0 ms … 152.1 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.08 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Furthermore, with this change we now perform a mostly constant number of
allocations when iterating. Before this change:
HEAP SUMMARY:
in use at exit: 13,603 bytes in 125 blocks
total heap usage: 1,006,620 allocs, 1,006,495 frees, 25,398,363 bytes allocated
After this change:
HEAP SUMMARY:
in use at exit: 13,603 bytes in 125 blocks
total heap usage: 6,623 allocs, 6,498 frees, 509,592 bytes allocated
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When calling `merged_iter_next_void()` we first check whether the iter
has been exhausted already. We already perform this check two levels
down the stack in `merged_iter_next_entry()` though, which makes this
check redundant.
Now if this check was there to accelerate the common case it might have
made sense to keep it. But the iterator being exhausted is rather the
uncommon case because you can expect most reftable stacks to contain
more than two refs.
Simplify the code by removing the check. As `merged_iter_next_void()` is
basically empty except for calling `merged_iter_next()` now, merge these
two functions. This also results in a tiny speedup when iterating over
many refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 125.6 ms ± 3.8 ms [User: 122.7 ms, System: 2.8 ms]
Range (min … max): 122.4 ms … 153.4 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 124.0 ms ± 3.9 ms [User: 121.1 ms, System: 2.8 ms]
Range (min … max): 120.1 ms … 156.4 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.01 ± 0.04 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The merged iterator uses a priority queue to order records so that we
can yielid them in the expected order. This priority queue of course
comes with some overhead as we need to add, compare and remove entries
in that priority queue.
In the general case, that overhead cannot really be avoided. But when we
have a single subiter left then there is no need to use the priority
queue anymore because the order is exactly the same as what that subiter
would return.
While having a single subiter may sound like an edge case, it happens
more frequently than one might think. In the most common scenario, you
can expect a repository to have a single large table that contains most
of the records and then a set of smaller tables which contain later
additions to the reftable stack. In this case it is quite likely that we
exhaust subiters of those smaller stacks before exhausting the large
table.
Special-case this and return records directly from the remaining
subiter. This results in a sizeable speedup when iterating over 1m refs
in a repository with a single table:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 135.4 ms ± 4.4 ms [User: 132.5 ms, System: 2.8 ms]
Range (min … max): 131.0 ms … 166.3 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 126.3 ms ± 3.9 ms [User: 123.3 ms, System: 2.8 ms]
Range (min … max): 122.7 ms … 157.0 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.07 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When advancing one of the subiters fails we immediately release
resources associated with that subiter. This is not necessary though as
we will release these resources when closing the merged iterator anyway.
Drop the logic and only release resources when the merged iterator is
done. This is a mere cleanup that should help reduce the cognitive load
when reading through the code.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Whenever we advance a subiter we first call `iterator_is_null()`. This
is not needed though because we only ever advance subiters which have
entries in the priority queue, and we do not end entries to the priority
queue when the subiter has been exhausted.
Drop the check as well as the now-unused function. This results in a
surprisingly big speedup:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 138.1 ms ± 4.4 ms [User: 135.1 ms, System: 2.8 ms]
Range (min … max): 133.4 ms … 167.3 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 134.4 ms ± 4.2 ms [User: 131.5 ms, System: 2.8 ms]
Range (min … max): 130.0 ms … 164.0 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.03 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
For each subiterator, the merged table needs to track their current
record. This record is owned by the priority queue though instead of by
the merged iterator. This is not optimal performance-wise.
For one, we need to move around records whenever we add or remove a
record from the priority queue. Thus, the bigger the entries the more
bytes we need to copy around. And compared to pointers, a reftable
record is rather on the bigger side. The other issue is that this makes
it harder to reuse the records.
Refactor the code so that the merged iterator tracks ownership of the
records per-subiter. Instead of having records in the priority queue, we
can now use mere pointers to the per-subiter records. This also allows
us to swap records between the caller and the per-subiter record instead
of doing an actual copy via `reftable_record_copy_from()`, which removes
the need to release the caller-provided record.
This results in a noticeable speedup when iterating through many refs.
The following benchmark iterates through 1 million refs:
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 145.5 ms ± 4.5 ms [User: 142.5 ms, System: 2.8 ms]
Range (min … max): 141.3 ms … 177.0 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 139.0 ms ± 4.7 ms [User: 136.1 ms, System: 2.8 ms]
Range (min … max): 134.2 ms … 182.2 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.05 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~)
This refactoring also allows a subsequent refactoring where we start
reusing memory allocated by the reftable records because we do not need
to release the caller-provided record anymore.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When advancing the merged iterator, we pop the topmost entry from its
priority queue and then advance the sub-iterator that the entry belongs
to, adding the result as a new entry. This is quite sensible in the case
where the merged iterator is used to actually iterate through records.
But the merged iterator is also used when we look up a single record,
only, so advancing the sub-iterator is wasted effort because we would
never even look at the result.
Instead of immediately advancing the sub-iterator, we can also defer
this to the next iteration of the merged iterator by storing the
intent-to-advance. This results in a small speedup when reading many
records. The following benchmark creates 10000 refs, which will also end
up with many ref lookups:
Benchmark 1: update-ref: create many refs (revision = HEAD~)
Time (mean ± σ): 337.2 ms ± 7.3 ms [User: 200.1 ms, System: 136.9 ms]
Range (min … max): 329.3 ms … 373.2 ms 100 runs
Benchmark 2: update-ref: create many refs (revision = HEAD)
Time (mean ± σ): 332.5 ms ± 5.9 ms [User: 197.2 ms, System: 135.1 ms]
Range (min … max): 327.6 ms … 359.8 ms 100 runs
Summary
update-ref: create many refs (revision = HEAD) ran
1.01 ± 0.03 times faster than update-ref: create many refs (revision = HEAD~)
While this speedup alone isn't really worth it, this refactoring will
also allow two additional optimizations in subsequent patches. First, it
will allow us to special-case when there is only a single sub-iter left
to circumvent the priority queue altogether. And second, it makes it
easier to avoid copying records to the caller.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `merged_iter` structure is not used anywhere outside of "merged.c",
but is declared in its header. Move it into the code file so that it is
clear that its implementation details are never exposed to anything.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The reftable priority queue is used by the merged iterator to yield
records from its sub-iterators in the expected order. Each entry has a
record corresponding to such a sub-iterator as well as an index that
indicates which sub-iterator the record belongs to. But while the
sub-iterators are tracked with a `size_t`, we store the index as an
`int` in the entry.
Fix this and use `size_t` consistently.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
More tests that are marked as "ref-files only" have been updated to
improve test coverage of reftable backend.
* ps/ref-tests-update-even-more:
t7003: ensure filter-branch prunes reflogs with the reftable backend
t2011: exercise D/F conflicts with HEAD with the reftable backend
t1405: remove unneeded cleanup step
t1404: make D/F conflict tests compatible with reftable backend
t1400: exercise reflog with gaps with reftable backend
t0410: convert tests to use DEFAULT_REPO_FORMAT prereq
t: move tests exercising the "files" backend
Teach "git checkout -p" and friends that "@" is a synonym for
"HEAD".
* gt/at-is-synonym-for-head-in-add-patch:
add -p tests: remove PERL prerequisites
add-patch: classify '@' as a synonym for 'HEAD'
"git column" has been taught to reject negative padding value, as
it would lead to nonsense behaviour including division by zero.
* kh/column-reject-negative-padding:
column: guard against negative padding
column: disallow negative padding
Adjust use of "rev-list --missing" in an existing tests so that it
does not depend on a buggy failure mode.
* jc/t9210-lazy-fix:
t9210: do not rely on lazy fetching to fail
The code to iterate over refs with the reftable backend has seen
some optimization.
* ps/reftable-iteration-perf:
reftable/reader: add comments to `table_iter_next()`
reftable/record: don't try to reallocate ref record name
reftable/block: swap buffers instead of copying
reftable/pq: allocation-less comparison of entry keys
reftable/merged: skip comparison for records of the same subiter
reftable/merged: allocation-less dropping of shadowed records
reftable/record: introduce function to compare records by key
"git apply" on a filesystem without filemode support have learned
to take a hint from what is in the index for the path, even when
not working with the "--index" or "--cached" option, when checking
the executable bit match what is required by the preimage in the
patch.
* cp/apply-core-filemode:
apply: code simplification
apply: correctly reverse patch's pre- and post-image mode bits
apply: ignore working tree filemode when !core.filemode
Integrate the reftable code into the refs framework as a backend.
* ps/reftable-backend:
refs/reftable: fix leak when copying reflog fails
ci: add jobs to test with the reftable backend
refs: introduce reftable backend
Commit 97e9d0b78a (trailer: find the end of the log message, 2023-10-20)
combined two code paths for finding the end of the log message. For the
"no_divider" case, we used to use find_trailer_end(), and that has now
been rolled into find_end_of_log_message(). But there's a regression;
that function returns early when no_divider is set, returning the whole
string.
That's not how find_trailer_end() behaved. Although it did skip the
"---" processing (which is what "no_divider" is meant to do), we should
still respect ignored_log_message_bytes(), which covers things like
comments, "commit -v" cut lines, and so on.
The bug is actually in the interpret-trailers command, but the obvious
way to experience it is by running "commit -v" with a "--trailer"
option. The new trailer will be added at the end of the verbose diff,
rather than before it (and consequently will be ignored entirely, since
everything after the diff's intro scissors line is thrown away).
I've added two tests here: one for interpret-trailers directly, which
shows the bug via the parsing routines, and one for "commit -v".
The fix itself is pretty simple: instead of returning early, no_divider
just skips the "---" handling but still calls ignored_log_message_bytes().
Reported-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In addition to the localized translation in 2.44, for zh_CN, we have
uniformly modified the translation of the word "commit-graph" to make it
more consistent with language usage habits.
Signed-off-by: Teng Long <dyroneteng@gmail.com>
After we upgraded actions/setup-go to v5, the following warning message
was reported every time we ran the CI.
Restore cache failed: Dependencies file is not found ...
Disable cache to suppress warning messages as described in the solution
below.
https://github.com/actions/setup-go/issues/427
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
When we upgraded GitHub Actions "mshick/add-pr-comment" to v2, the
following warning message was reported every time we ran the CI.
Unexpected input(s) 'repo-token-user-login', valid inputs ...
Removed the obsolete parameter "repo-token-user-login" to suppress
warning messages.
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
