| Age | Commit message (Collapse) | Author | Files | Lines |
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Code simplification by removing ineffective optimization.
* ps/ref-transaction-hook:
refs: remove lookup cache for reference-transaction hook
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When adding the reference-transaction hook, there were concerns about
the performance impact it may have on setups which do not make use of
the new hook at all. After all, it gets executed every time a reftx is
prepared, committed or aborted, which linearly scales with the number of
reference-transactions created per session. And as there are code paths
like `git push` which create a new transaction for each reference to be
updated, this may translate to calling `find_hook()` quite a lot.
To address this concern, a cache was added with the intention to not
repeatedly do negative hook lookups. Turns out this cache caused a
regression, which was fixed via e5256c82e5 (refs: fix interleaving hook
calls with reference-transaction hook, 2020-08-07). In the process of
discussing the fix, we realized that the cache doesn't really help even
in the negative-lookup case. While performance tests added to benchmark
this did show a slight improvement in the 1% range, this really doesn't
warrent having a cache. Furthermore, it's quite flaky, too. E.g. running
it twice in succession produces the following results:
Test master pks-reftx-hook-remove-cache
--------------------------------------------------------------------------
1400.2: update-ref 2.79(2.16+0.74) 2.73(2.12+0.71) -2.2%
1400.3: update-ref --stdin 0.22(0.08+0.14) 0.21(0.08+0.12) -4.5%
Test master pks-reftx-hook-remove-cache
--------------------------------------------------------------------------
1400.2: update-ref 2.70(2.09+0.72) 2.74(2.13+0.71) +1.5%
1400.3: update-ref --stdin 0.21(0.10+0.10) 0.21(0.08+0.13) +0.0%
One case notably absent from those benchmarks is a single executable
searching for the hook hundreds of times, which is exactly the case for
which the negative cache was added. p1400.2 will spawn a new update-ref
for each transaction and p1400.3 only has a single reference-transaction
for all reference updates. So this commit adds a third benchmark, which
performs an non-atomic push of a thousand references. This will create a
new reference transaction per reference. But even for this case, the
negative cache doesn't consistently improve performance:
Test master pks-reftx-hook-remove-cache
--------------------------------------------------------------------------
1400.4: nonatomic push 6.63(6.50+0.13) 6.81(6.67+0.14) +2.7%
1400.4: nonatomic push 6.35(6.21+0.14) 6.39(6.23+0.16) +0.6%
1400.4: nonatomic push 6.43(6.31+0.13) 6.42(6.28+0.15) -0.2%
So let's just remove the cache altogether to simplify the code.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When PERF_EXTRA is enabled, p5302 checks the performance of index-pack
with various numbers of threads. This can be useful for deciding what
the default should be (which is currently capped at 3 threads based on
the results of this script).
However, we only go up to 8 threads, and modern machines may have more.
Let's get the number of CPUs from test-tool, and test various numbers of
threads between one and that maximum.
Note that the current tests aren't all identical, as we have to set
GIT_FORCE_THREADS for the --threads=1 test (which measures the overhead
of starting a single worker thread versus the "0" case of using the main
thread). To keep the loop simple, we'll keep the "0" case out of it, and
set GIT_FORCE_THREADS=1 for all of the other cases (it's a noop for all
but the "1" case, since numbers higher than 1 would always need
threads).
Note also that we could skip running "test-tool" if PERF_EXTRA isn't
set. However, there's some small value in knowing the number of threads,
so that we can mark each test as skipped in the output.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The primary function of the perf suite is to detect regressions (or
improvements) between versions of Git. The only numbers we show a direct
comparison for are timings between the same test run on two different
versions.
However, it can sometimes be used to collect other information. For
instance, p5302 runs the same index-pack operation with different thread
counts. The output doesn't directly compare these, but anybody
interested in working on index-pack can manually compare the results.
For a normal regression run of the full perf-suite, though, this incurs
a significant cost to generate numbers nobody will actually look at;
about 25% of the total time of the test suite is spent in p5302. And the
low-thread-count runs are the most expensive part of it, since they're
(unsurprisingly) not using as many threads.
Let's skip these tests by default, but make it possible for people
working on index-pack to still run them by setting an environment
variable. Rather than make this specific to p5302, let's introduce a
generic mechanism. This makes it possible to run the full suite with
every possible test if somebody really wants to burn some CPU.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The low-level reference transactions used to update references are
currently completely opaque to the user. While certainly desirable in
most usecases, there are some which might want to hook into the
transaction to observe all queued reference updates as well as observing
the abortion or commit of a prepared transaction.
One such usecase would be to have a set of replicas of a given Git
repository, where we perform Git operations on all of the repositories
at once and expect the outcome to be the same in all of them. While
there exist hooks already for a certain subset of Git commands that
could be used to implement a voting mechanism for this, many others
currently don't have any mechanism for this.
The above scenario is the motivation for the new "reference-transaction"
hook that reaches directly into Git's reference transaction mechanism.
The hook receives as parameter the current state the transaction was
moved to ("prepared", "committed" or "aborted") and gets via its
standard input all queued reference updates. While the exit code gets
ignored in the "committed" and "aborted" states, a non-zero exit code in
the "prepared" state will cause the transaction to be aborted
prematurely.
Given the usecase described above, a voting mechanism can now be
implemented via this hook: as soon as it gets called, it will take all
of stdin and use it to cast a vote to a central service. When all
replicas of the repository agree, the hook will exit with zero,
otherwise it will abort the transaction by returning non-zero. The most
important upside is that this will catch _all_ commands writing
references at once, allowing to implement strong consistency for
reference updates via a single mechanism.
In order to test the impact on the case where we don't have any
"reference-transaction" hook installed in the repository, this commit
introduce two new performance tests for git-update-refs(1). Run against
an empty repository, it produces the following results:
Test origin/master HEAD
--------------------------------------------------------------------
1400.2: update-ref 2.70(2.10+0.71) 2.71(2.10+0.73) +0.4%
1400.3: update-ref --stdin 0.21(0.09+0.11) 0.21(0.07+0.14) +0.0%
The performance test p1400.2 creates, updates and deletes a branch a
thousand times, thus averaging runtime of git-update-refs over 3000
invocations. p1400.3 instead calls `git-update-refs --stdin` three times
and queues a thousand creations, updates and deletes respectively.
As expected, p1400.3 consistently shows no noticeable impact, as for
each batch of updates there's a single call to access(3P) for the
negative hook lookup. On the other hand, for p1400.2, one can see an
impact caused by this patchset. But doing five runs of the performance
tests where each one was run with GIT_PERF_REPEAT_COUNT=10, the overhead
ranged from -1.5% to +1.1%. These inconsistent performance numbers can
be explained by the overhead of spawning 3000 processes. This shows that
the overhead of assembling the hook path and executing access(3P) once
to check if it's there is mostly outweighed by the operating system's
overhead.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Sometimes a bitmap traversal still has to walk some commits manually,
because those commits aren't included in the bitmap packfile (e.g., due
to a push or commit since the last full repack). If we're given an
object filter, we don't pass it down to this traversal. It's not
necessary for correctness because the bitmap code has its own filters to
post-process the bitmap result (which it must, to filter out the objects
that _are_ mentioned in the bitmapped packfile).
And with blob filters, there was no performance reason to pass along
those filters, either. The fill-in traversal could omit them from the
result, but it wouldn't save us any time to do so, since we'd still have
to walk each tree entry to see if it's a blob or not.
But now that we support tree filters, there's opportunity for savings. A
tree:depth=0 filter means we can avoid accessing trees entirely, since
we know we won't them (or any of the subtrees or blobs they point to).
The new test in p5310 shows this off (the "partial bitmap" state is one
where HEAD~100 and its ancestors are all in a bitmapped pack, but
HEAD~100..HEAD are not). Here are the results (run against linux.git):
Test HEAD^ HEAD
-------------------------------------------------------------------------------------------------
[...]
5310.16: rev-list with tree filter (partial bitmap) 0.19(0.17+0.02) 0.03(0.02+0.01) -84.2%
The absolute number of savings isn't _huge_, but keep in mind that we
only omitted 100 first-parent links (in the version of linux.git here,
that's 894 actual commits). In a more pathological case, we might have a
much larger proportion of non-bitmapped commits. I didn't bother
creating such a case in the perf script because the setup is expensive,
and this is plenty to show the savings as a percentage.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In the previous patch, we made it easy to define other filters that
exclude all objects of a certain type. Use that in order to implement
bitmap-level filtering for the '--filter=tree:<n>' filter when 'n' is
equal to 0.
The general case is not helped by bitmaps, since for values of 'n > 0',
the object filtering machinery requires a full-blown tree traversal in
order to determine the depth of a given tree. Caching this is
non-obvious, too, since the same tree object can have a different depth
depending on the context (e.g., a tree was moved up in the directory
hierarchy between two commits).
But, the 'n = 0' case can be helped, and this patch does so. Running
p5310.11 in this tree and on master with the kernel, we can see that
this case is helped substantially:
Test master this tree
--------------------------------------------------------------------------------
5310.11: rev-list count with tree:0 10.68(10.39+0.27) 0.06(0.04+0.01) -99.4%
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The custom hash function used by "git fast-import" has been
replaced with the one from hashmap.c, which gave us a nice
performance boost.
* jk/fast-import-use-hashmap:
fast-import: replace custom hash with hashmap.c
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We use a custom hash in fast-import to store the set of objects we've
imported so far. It has a fixed set of 2^16 buckets and chains any
collisions with a linked list. As the number of objects grows larger
than that, the load factor increases and we degrade to O(n) lookups and
O(n^2) insertions.
We can scale better by using our hashmap.c implementation, which will
resize the bucket count as we grow. This does incur an extra memory cost
of 8 bytes per object, as hashmap stores the integer hash value for each
entry in its hashmap_entry struct (which we really don't care about
here, because we're just reusing the embedded object hash). But I think
the numbers below justify this (and our per-object memory cost is
already much higher).
I also looked at using khash, but it seemed to perform slightly worse
than hashmap at all sizes, and worse even than the existing code for
small sizes. It's also awkward to use here, because we want to look up a
"struct object_entry" from a "struct object_id", and it doesn't handle
mismatched keys as well. Making a mapping of object_id to object_entry
would be more natural, but that would require pulling the embedded oid
out of the object_entry or incurring an extra 32 bytes per object.
In a synthetic test creating as many cheap, tiny objects as possible
perl -e '
my $bits = shift;
my $nr = 2**$bits;
for (my $i = 0; $i < $nr; $i++) {
print "blob\n";
print "data 4\n";
print pack("N", $i);
}
' $bits | git fast-import
I got these results:
nr_objects master khash hashmap
2^20 0m4.317s 0m5.109s 0m3.890s
2^21 0m10.204s 0m9.702s 0m7.933s
2^22 0m27.159s 0m17.911s 0m16.751s
2^23 1m19.038s 0m35.080s 0m31.963s
2^24 4m18.766s 1m10.233s 1m6.793s
which points to hashmap as the winner. We didn't have any perf tests for
fast-export or fast-import, so I added one as a more real-world case.
It uses an export without blobs since that's significantly cheaper than
a full one, but still is an interesting case people might use (e.g., for
rewriting history). It will emphasize this change in some ways (as a
percentage we spend more time making objects and less shuffling blob
bytes around) and less in others (the total object count is lower).
Here are the results for linux.git:
Test HEAD^ HEAD
----------------------------------------------------------------------------
9300.1: export (no-blobs) 67.64(66.96+0.67) 67.81(67.06+0.75) +0.3%
9300.2: import (no-blobs) 284.04(283.34+0.69) 198.09(196.01+0.92) -30.3%
It only has ~5.2M commits and trees, so this is a larger effect than I
expected (the 2^23 case above only improved by 50s or so, but here we
gained almost 90s). This is probably due to actually performing more
object lookups in a real import with trees and commits, as opposed to
just dumping a bunch of blobs into a pack.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Commit 645c432d61 (pack-objects: use reachability bitmap index when
generating non-stdout pack, 2016-09-10) added two timing tests for
packing to an on-disk file, both with and without bitmaps. However, the
non-bitmap one isn't interesting to have as part of p5310's regression
suite. It _could_ be used as a baseline to show off the improvement in
the bitmap case, but:
- the point of the t/perf suite is to find performance regressions,
and it won't help with that. We don't compare the numbers between
two tests (which the perf suite has no idea are even related), and
any change in its numbers would have nothing to do with bitmaps.
- it did show off the improvement in the commit message of 645c432d61,
but it wasn't even necessary there. The bitmap case already shows an
improvement (because before the patch, it behaved the same as the
non-bitmap case), and the perf suite is even able to show the
difference between the before and after measurements.
On top of that, it's one of the most expensive tests in the suite,
clocking in around 60s for linux.git on my machine (as compared to 16s
for the bitmapped version). And by default when using "./run", we'd run
it three times!
So let's just drop it. It's not useful and is adding minutes to perf
runs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Just as rev-list recently learned to combine filters and bitmaps, let's
do the same for pack-objects. The infrastructure is all there; we just
need to pass along our filter options, and the pack-bitmap code will
decide to use bitmaps or not.
This unsurprisingly makes things faster for partial clones of large
repositories (here we're cloning linux.git):
Test HEAD^ HEAD
------------------------------------------------------------------------------
5310.11: simulated partial clone 38.94(37.28+5.87) 11.06(11.27+4.07) -71.6%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Just as the previous commit implemented BLOB_NONE, we can support
BLOB_LIMIT filters by looking at the sizes of any blobs in the result
and unsetting their bits as appropriate. This is slightly more expensive
than BLOB_NONE, but still produces a noticeable speedup (these results
are on git.git):
Test HEAD~2 HEAD
------------------------------------------------------------------------------------
5310.9: rev-list count with blob:none 1.80(1.77+0.02) 0.22(0.20+0.02) -87.8%
5310.10: rev-list count with blob:limit=1k 1.99(1.96+0.03) 0.29(0.25+0.03) -85.4%
The implementation is similar to the BLOB_NONE one, with the exception
that we have to go object-by-object while walking the blob-type bitmap
(since we can't mask out the matches, but must look up the size
individually for each blob). The trick with using ctz64() is taken from
show_objects_for_type(), which likewise needs to find individual bits
(but wants to quickly skip over big chunks without blobs).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We can easily support BLOB_NONE filters with bitmaps. Since we know the
types of all of the objects, we just need to clear the result bits of
any blobs.
Note two subtleties in the implementation (which I also called out in
comments):
- we have to include any blobs that were specifically asked for (and
not reached through graph traversal) to match the non-bitmap version
- we have to handle in-pack and "ext_index" objects separately.
Arguably prepare_bitmap_walk() could be adding these ext_index
objects to the type bitmaps. But it doesn't for now, so let's match
the rest of the bitmap code here (it probably wouldn't be an
efficiency improvement to do so since the cost of extending those
bitmaps is about the same as our loop here, but it might make the
code a bit simpler).
Here are perf results for the new test on git.git:
Test HEAD^ HEAD
--------------------------------------------------------------------------------
5310.9: rev-list count with blob:none 1.67(1.62+0.05) 0.22(0.21+0.02) -86.8%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Ever since we added reachability bitmap support, we've been able to use
it with rev-list to get the full list of objects, like:
git rev-list --objects --use-bitmap-index --all
But you can't do so without --objects, since we weren't ready to just
show the commits. However, the internals of the bitmap code are mostly
ready for this: they avoid opening up trees when walking to fill in the
bitmaps. We just need to actually pass in the rev_info to
traverse_bitmap_commit_list() so it knows which types to bother
triggering our callback for.
For completeness, the perf test now covers both the existing --objects
case, as well as the new commits-only behavior (the objects one got way
faster when we introduced bitmaps, but obviously isn't improved now).
Here are numbers for linux.git:
Test HEAD^ HEAD
------------------------------------------------------------------------
5310.7: rev-list (commits) 8.29(8.10+0.19) 1.76(1.72+0.04) -78.8%
5310.8: rev-list (objects) 8.06(7.94+0.12) 8.14(7.94+0.13) +1.0%
That run was cheating a little, as I didn't have any commit-graph in the
repository, and we'd built it by default these days when running git-gc.
Here are numbers with a commit-graph:
Test HEAD^ HEAD
------------------------------------------------------------------------
5310.7: rev-list (commits) 0.70(0.58+0.12) 0.51(0.46+0.04) -27.1%
5310.8: rev-list (objects) 6.20(6.09+0.10) 6.27(6.16+0.11) +1.1%
Still an improvement, but a lot less impressive.
We could have the perf script remove any commit-graph to show the
out-sized effect, but it probably makes sense to leave it in what would
be a more typical setup.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In a repository with many packfiles, the cost of the procedure that
avoids registering the same packfile twice was unnecessarily high
by using an inefficient search algorithm, which has been corrected.
* cs/store-packfiles-in-hashmap:
packfile.c: speed up loading lots of packfiles
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Test cleanup.
* jk/perf-wo-git-dot-pm:
t/perf: don't depend on Git.pm
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PerfTest fix to avoid stale result mixed up with the latest round
of test results.
* tg/perf-remove-stale-result:
perf-lib: use a single filename for all measurement types
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When loading packfiles on start-up, we traverse the internal packfile
list once per file to avoid reloading packfiles that have already
been loaded. This check runs in quadratic time, so for poorly
maintained repos with a large number of packfiles, it can be pretty
slow.
Add a hashmap containing the packfile names as we load them so that
the average runtime cost of checking for already-loaded packs becomes
constant.
Add a perf test to p5303 to show speed-up.
The existing p5303 test runtimes are dominated by other factors and do
not show an appreciable speed-up. The new test in p5303 clearly exposes
a speed-up in bad cases. In this test we create 10,000 packfiles and
measure the start-up time of git rev-parse, which does little else
besides load in the packs.
Here are the numbers for the new p5303 test:
Test HEAD^ HEAD
---------------------------------------------------------------------
5303.12: load 10,000 packs 1.03(0.92+0.10) 0.12(0.02+0.09) -88.3%
Signed-off-by: Colin Stolley <cstolley@runbox.com>
Helped-by: Jeff King <peff@peff.net>
[jc: squashed the change to call hashmap in install_packed_git() by peff]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Code clean-up.
* jk/optim-in-pack-idx-conversion:
pack-objects: avoid pointless oe_map_new_pack() calls
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The perf suite's aggregate.perl depends on Git.pm, which is a mild
annoyance if you've built git with NO_PERL. It turns out that the only
thing we use it for is a single call of the command_oneline() helper.
We can just replace this with backticks or similar.
Annoyingly, perl has no backtick equivalent that avoids a shell eval,
which means our $arg would require quoting. This probably doesn't matter
for our purposes, but it's better to be safe and model good style. So
we'll just provide a short helper around open(), which takes its
arguments as a list.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The perf tests write files recording the results of tests. These
results are later aggregated by 'aggregate.perl'. If the tests are run
multiple times, those results are overwritten by the new results. This
works just fine as long as there are only perf tests measuring the
times, whose results are stored in "$base".times files.
However 22bec79d1a ("t/perf: add infrastructure for measuring sizes",
2018-08-17) introduced a new type of test for measuring the size of
something. The results of this are written to "$base".size files.
"$base" is essentially made up of the basename of the script plus the
test number. So if test numbers shift because a new test was
introduced earlier in the script we might end up with both a ".times"
and a ".size" file for the same test. In the aggregation script the
".times" file is preferred over the ".size" file, so some size tests
might end with performance numbers from a previous run of the test.
This is mainly relevant when writing perf tests that check both
performance and sizes, and can get quite confusing during
developement.
We could fix this by doing a more thorough job of cleaning out old
".times" and ".size" files before running each test. However, an even
easier solution is to just use the same filename for both types of
measurement, meaning we'll always overwrite the previous result. We
don't even need to change the file format to distinguish the two;
aggregate.perl already decides which is which based on a regex of the
content (this may become ambiguous if we add new types in the future,
but we could easily add a header field to the file at that point).
Based on an initial patch from Thomas Gummerer, who discovered the
problem and did all of the analysis (which I stole for the commit
message above):
https://public-inbox.org/git/20191119185047.8550-1-t.gummerer@gmail.com/
Helped-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch fixes an extreme slowdown in pack-objects when you have more
than 1023 packs. See below for numbers.
Since 43fa44fa3b (pack-objects: move in_pack out of struct object_entry,
2018-04-14), we use a complicated system to save some per-object memory.
Each object_entry structs gets a 10-bit field to store the index of the
pack it's in. We map those indices into pointers using
packing_data->in_pack_by_idx, which we initialize at the start of the
program. If we have 2^10 or more packs, then we instead create an array
of pack pointers, one per object. This is packing_data->in_pack.
So far so good. But there's one other tricky case: if a new pack arrives
after we've initialized in_pack_by_idx, it won't have an index yet. We
solve that by calling oe_map_new_pack(), which just switches on the fly
to the less-optimal in_pack mechanism, allocating the array and
back-filling it for already-seen objects.
But that logic kicks in even when we've switched to it already (whether
because we really did see a new pack, or because we had too many packs
in the first place). The result doesn't produce a wrong outcome, but
it's very slow. What happens is this:
- imagine you have a repo with 500k objects and 2000 packs that you
want to repack.
- before looking at any objects, we call prepare_in_pack_by_idx(). It
starts allocating an index for each pack. On the 1024th pack, it
sees there are too many, so it bails, leaving in_pack_by_idx as
NULL.
- while actually adding objects to the packing list, we call
oe_set_in_pack(), which checks whether the pack already has an
index. If it's one of the packs after the first 1023, then it
doesn't have one, and we'll call oe_map_new_pack().
But there's no useful work for that function to do. We're already
using in_pack, so it just uselessly walks over the complete list of
objects, trying to backfill in_pack.
And we end up doing this for almost 1000 packs (each of which may be
triggered by more than one object). And each time it triggers, we
may iterate over up to 500k objects. So in the absolute worst case,
this is quadratic in the number of objects.
The solution is simple: we don't need to bother checking whether the
pack has an index if we've already converted to using in_pack, since by
definition we're not going to use it. So we can just push the "does the
pack have a valid index" check down into that half of the conditional,
where we know we're going to use it.
The current test in p5303 sadly doesn't notice this problem, since it
maxes out at 1000 packs. If we add a new test to it at 2000 packs, it
does show the improvement:
Test HEAD^ HEAD
----------------------------------------------------------------------
5303.12: repack (2000) 26.72(39.68+0.67) 15.70(28.70+0.66) -41.2%
However, these many-pack test cases are rather expensive to run, so
adding larger and larger numbers isn't appealing. Instead, we can show
it off more easily by using GIT_TEST_FULL_IN_PACK_ARRAY, which forces us
into the absolute worst case: no pack has an index, so we'll trigger
oe_map_new_pack() pointlessly for every single object, making it truly
quadratic.
Here are the numbers (on git.git) with the included change to p5303:
Test HEAD^ HEAD
----------------------------------------------------------------------
5303.3: rev-list (1) 2.05(1.98+0.06) 2.06(1.99+0.06) +0.5%
5303.4: repack (1) 33.45(33.46+0.19) 2.75(2.73+0.22) -91.8%
5303.6: rev-list (50) 2.07(2.01+0.06) 2.06(2.01+0.05) -0.5%
5303.7: repack (50) 34.21(35.18+0.16) 3.49(4.50+0.12) -89.8%
5303.9: rev-list (1000) 2.87(2.78+0.08) 2.88(2.80+0.07) +0.3%
5303.10: repack (1000) 41.26(51.30+0.47) 10.75(20.75+0.44) -73.9%
Again, those improvements aren't realistic for the 1-pack case (because
in the real world, the full-array solution doesn't kick in), but it's
more useful to be testing the more-complicated code path.
While we're looking at this issue, we'll tweak one more thing: in
oe_map_new_pack(), we call REALLOC_ARRAY(pack->in_pack). But we'd never
expect to get here unless we're back-filling it for the first time, in
which case it would be NULL. So let's switch that to ALLOC_ARRAY() for
clarity, and add a BUG() to document the expectation. Unfortunately this
code isn't well-covered in the test suite because it's inherently racy
(it only kicks in if somebody else adds a new pack while we're in the
middle of repacking).
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
Reported-by: Jens Schleusener <Jens.Schleusener@fossies.org>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
There are two perf scripts numbered p5600, but with otherwise different
names ("clone-reference" versus "partial-clone"). We store timing
results in files named after the whole script, so internally we don't
get confused between the two. But "aggregate.perl" just prints the test
number for each result, giving multiple entries for "5600.3". It also
makes it impossible to skip one test but not the other with
GIT_SKIP_TESTS.
Let's renumber the one that appeared later (by date -- the source of the
problem is that the two were developed on independent branches). For the
non-perf test suite, our test-lint rule would have complained about this
when the two were merged, but t/perf never learned that trick.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
When we receive a remote ref update to sha1 "X", we want to check that
we have all of the objects needed by "X". We can assume that our
repository is not currently corrupted, and therefore if we have a ref
pointing at "Y", we have all of its objects. So we can stop our
traversal from "X" as soon as we hit "Y".
If we make the same non-corruption assumption about any repositories we
use to store alternates, then we can also use their ref tips to shorten
the traversal.
This is especially useful when cloning with "--reference", as we
otherwise do not have any local refs to check against, and have to
traverse the whole history, even though the other side may have sent us
few or no objects. Here are results for the included perf test (which
shows off more or less the maximal savings, getting one new commit and
sharing the whole history):
Test HEAD^ HEAD
--------------------------------------------------------------------
[on git.git]
5600.3: clone --reference 2.94(2.86+0.08) 0.09(0.08+0.01) -96.9%
[on linux.git]
5600.3: clone --reference 45.74(45.34+0.41) 0.36(0.30+0.08) -99.2%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
Performance test framework has been broken and measured the version
of Git that happens to be on $PATH, not the specified one to
measure, for a while, which has been corrected.
* ab/perf-installed-fix:
perf-lib.sh: forbid the use of GIT_TEST_INSTALLED
perf tests: add "bindir" prefix to git tree test results
perf-lib.sh: remove GIT_TEST_INSTALLED from perf-lib.sh
perf-lib.sh: make "./run <revisions>" use the correct gits
perf aggregate: remove GIT_TEST_INSTALLED from --codespeed
perf README: correct docs for 3c8f12c96c regression
|
|
The script to aggregate perf result unconditionally depended on
libjson-perl even though it did not have to, which has been
corrected.
* jk/perf-aggregate-wo-libjson:
t/perf: depend on perl JSON only when using --codespeed
|
|
Fix index-pack perf test so that the repeated invocations always
run in an empty repository, which emulates the initial clone
situation better.
* jk/p5302-avoid-collision-check-cost:
p5302: create the repo in each index-pack test
|
|
The connectivity bitmaps are created by default in bare
repositories now; also the pathname hash-cache is created by
default to avoid making crappy deltas when repacking.
* ew/repack-with-bitmaps-by-default:
pack-objects: default to writing bitmap hash-cache
t5310: correctly remove bitmaps for jgit test
repack: enable bitmaps by default on bare repos
|
|
During an initial "git clone --depth=..." partial clone, it is
pointless to spend cycles for a large portion of the connectivity
check that enumerates and skips promisor objects (which by
definition is all objects fetched from the other side). This has
been optimized out.
* js/partial-clone-connectivity-check:
t/perf: add perf script for partial clones
clone: do faster object check for partial clones
|
|
As noted in preceding commits setting GIT_TEST_INSTALLED has never
been supported or documented, and as noted in an earlier t/perf/README
change to the extent that it's been documented nobody's notices that
the example hasn't worked since 3c8f12c96c ("test-lib: reorder and
include GIT-BUILD-OPTIONS a lot earlier", 2012-06-24).
We could directly support GIT_TEST_INSTALLED for invocations without
the "run" script, such as:
GIT_TEST_INSTALLED=../../ ./p0000-perf-lib-sanity.sh
GIT_TEST_INSTALLED=/home/avar/g/git ./p0000-perf-lib-sanity.sh
But while not having this "error" will "work", it won't write the the
resulting "test-results/*" files to the right place, and thus a
subsequent call to aggregate.perl won't work as expected.
Let's just tell the user that they need to use the "run" script,
which'll correctly deal with this and set the right
PERF_RESULTS_PREFIX.
If someone's in desperate need of bypassing "run" for whatever reason
they can trivially do so by setting "PERF_SET_GIT_TEST_INSTALLED", but
not we won't have people who expect GIT_TEST_INSTALLED to just work
wondering why their aggregation doesn't work, even though they're
running the right "git".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
Change the output file names in test-results/ to be
"test-results/bindir_<munged dir>" rather than just
"test-results/<munged dir>".
This is for consistency with the "build_" directories we have for
built revisions, i.e. "test-results/build_<SHA-1>".
There's no user-visible functional changes here, it just makes it
easier to see at a glance what "test-results" files are of what "type"
as they're all explicitly grouped together now, and to grep this code
to find both the run_dirs_helper() implementation and its
corresponding aggregate.perl code.
Note that we already guarantee that the rest of the
PERF_RESULTS_PREFIX is an absolute path, and since it'll start with
e.g. "/" which we munge to "_" we'll up with a readable string like
"bindir_home_avar[...]".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
Follow-up my preceding change which fixed the immediate "./run
<revisions>" regression in 0baf78e7bc ("perf-lib.sh: rely on
test-lib.sh for --tee handling", 2019-03-15) and entirely get rid of
GIT_TEST_INSTALLED from perf-lib.sh (and aggregate.perl).
As noted in that change the dance we're doing with GIT_TEST_INSTALLED
perf-lib.sh isn't necessary, but there I was doing the most minimal
set of changes to quickly fix a regression.
But it's much simpler to never deal with the "GIT_TEST_INSTALLED" we
were setting in perf-lib.sh at all. Instead the run_dirs_helper() sets
the previously inferred $PERF_RESULTS_PREFIX directly.
Setting this at the callsite that's already best positioned to
exhaustively know about all the different cases we need to handle
where PERF_RESULTS_PREFIX isn't what we want already (the empty
string) makes the most sense. In one-off cases like:
./run ./p0000-perf-lib-sanity.sh
./p0000-perf-lib-sanity.sh
We'll just do the right thing because PERF_RESULTS_PREFIX will be
empty, and test-lib.sh takes care of finding where our git is.
Any refactoring of this code needs to change both the shell code and
the Perl code in aggregate.perl, because when running e.g.:
./run ../../ -- <test>
The "../../" path to a relative bindir needs to be munged to a
filename containing the results, and critically aggregate.perl does
not get passed the path to those aggregations, just "../..".
Let's fix cases where aggregate.perl would print e.g. ".." in its
report output for this, and "git" for "/home/avar/g/git", i.e. it
would always pick the last element. Now'll always print the full path
instead.
This also makes the code sturdier, e.g. you can feed "../.." to
"./run" and then an absolute path to the aggregate.perl script, as
long as the absolute path and "../.." resolved to the same directory
printing the aggregation will work.
Also simplify the "[_*]" on the RHS of "tr -c", we're trimming
everything to "_", so we don't need that.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
Fix a really bad regression in 0baf78e7bc ("perf-lib.sh: rely on
test-lib.sh for --tee handling", 2019-03-15). Since that change all
runs of different <revisions> of git have used the git found in the
user's $PATH, e.g. /usr/bin/git instead of the <revision> we just
built and wanted to performance test.
The problem starts with GIT_TEST_INSTALLED not working like our
non-perf tests with the "run" script. I.e. you can't run performance
tests against a given installed git. Instead we expect to use it
ourselves to point GIT_TEST_INSTALLED to the <revision> we just built.
However, we had been relying on '$(cd "$GIT_TEST_INSTALLED" && pwd)'
to resolve that relative $GIT_TEST_INSTALLED to an absolute
path *before* test-lib.sh was loaded, in cases where it was
e.g. "build/<rev>/bin-wrappers" and we wanted "<abs_path>build/...".
This change post-dates another proposed solution by a few days[1], I
didn't notice that version when I initially wrote this. I'm doing the
most minimal thing to solve the regression here, a follow-up change
will move this result prefix selection logic entirely into the "run"
script.
This makes e.g. these cases all work:
./run . $PWD/../../ origin/master origin/next HEAD -- <tests>
As well as just a plain one-off:
./run <tests>
And, since we're passing down the new GIT_PERF_DIR_MYDIR_REL we make
sure the bug relating to aggregate.perl not finding our files as
described in 0baf78e7bc doesn't happen again.
What *doesn't* work is setting GIT_TEST_INSTALLED to a relative path,
this will subtly fail in test-lib.sh. This has always been the case
even before 0baf78e7bc, and as documented in t/README the
GIT_TEST_INSTALLED variable should be set to an absolute path (needs
to be set "to the bindir", which is always absolute), and the "perf"
framework expects to munge it itself.
Perhaps that should be dealt with in the future to allow manually
setting GIT_TEST_INSTALLED, but as a preceding commit showed the user
can just use the "run" script, which'll also pick the right output
directory for the test results as expected by aggregate.perl.
1. https://public-inbox.org/git/20190502222409.GA15631@sigill.intra.peff.net/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
Remove the setting of the "environment" from the --codespeed output. I
don't think this is useful, and it helps with a later refactoring
where we GIT_TEST_INSTALLED stop munging/reading GIT_TEST_INSTALLED in
the perf tests in so many places.
This was added in 05eb1c37ed ("perf/aggregate: implement codespeed
JSON output", 2018-01-05), but since the "run" scripts uses
"GIT_TEST_INSTALLED" internally this was only ever useful for one-off
runs of a single revision as all the "environment" values would be
ones for whatever directory the "run" script ran last.
Let's instead fall back on the "uname -r" case, which is the sort of
thing the environment should be set to, not something that duplicates
other parts of the codpseed output. For setting the "environment" to
something custom the perf.repoName variable can be used. See
19cf57a92e ("perf/run: read GIT_PERF_REPO_NAME from perf.repoName",
2018-01-05).
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
Since 3c8f12c96c ("test-lib: reorder and include GIT-BUILD-OPTIONS a
lot earlier", 2012-06-24) the suggested advice of overriding
GIT_BUILD_DIR has not worked. We've printed a hard error like this
given e.g. GIT_BUILD_DIR=/home/avar/g/git:
/bin-wrappers/git is not executable; using GIT_EXEC_PATH
error: You haven't built things yet, have you?
Let's just suggest that the user run other gits via the "run"
script. That'll do the right thing for setting the path to the other
git, and running the "aggregate.perl" scripts afterwards will work.
As an aside, if setting GIT_BUILD_DIR had still worked, then the
MODERN_GIT feature/fix added in 1a0962dee5 ("t/perf: fix regression in
testing older versions of git", 2016-06-22) would have broke.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
|
|
We don't cover the partial clone feature at all in t/perf. Let's at
least run a few basic tests so that we'll notice any regressions.
We'll do a no-blob clone, and split it into two parts: the actual object
transfer, and the subsequent checkout (which will of course require
another transfer to get the blobs). That will help us more clearly
assess the performance of each.
There are obviously a lot more possibilities besides just a no-blob
partial clone, but this should serve as a canary that alerts us to any
generic slow-downs (and we can add more tests later for cases that
aren't exercised here).
There are a few non-ideal things here that make this not an entirely
accurate test, but are probably OK for our purposes:
1. We have to do some extra prep/cleanup work inside the timing tests,
since they impact the on-disk state and the perf harness may run
each one multiple times.
In practice this is probably OK, since these bits should be much
less expensive than the operations we are measuring.
2. The clone time is likely to be dominated by the server's object
enumeration. In the real world, a repo large enough to drive people
to partial clones is likely to have reachability bitmaps enabled.
And in the opposite direction, our object transfer is happening at
the speed of a local pipe, whereas in the real world it would
bottle-neck on the network.
So any percentage speedups should be taken with a grain of salt.
But hopefully any regressions will produce enough of an effect to
be noticeable.
This script also demonstrates the recent improvement from dfa33a298d
(clone: do faster object check for partial clones, 2019-04-19):
Test dfa33a298d^ dfa33a298d
-------------------------------------------------------------------------
5600.2: clone without blobs 18.41(22.72+1.09) 6.83(11.65+0.50) -62.9%
5600.3: checkout of result 1.82(3.24+0.26) 1.84(3.24+0.26) +1.1%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
Performance fix for "rev-list --parents -- pathspec".
* jk/revision-rewritten-parents-in-prio-queue:
revision: use a prio_queue to hold rewritten parents
|
|
Commit 05eb1c37ed (perf/aggregate: implement codespeed JSON output,
2018-01-05) added a dependency on the perl JSON module to show output
from aggregate.perl, but we only need it when the user asks for
--codespeed output. While the module is pretty common, it's not part of
the base system, and this dependency can get in the way of producing the
default human-readable output.
Let's bump the "use" down to a "require" in the code path that needs it,
which will be interpreted at run-time instead of compile-time. People
not using "--codespeed" won't even load the module, and anybody using it
should see the same results (including the same perl error if they don't
have it).
Note that this skips the importing step, so we'll have to fully qualify
our function call. We could accomplish the same thing in other ways.
E.g., calling JSON->import() ourselves, or wrapping "use JSON" in an
eval. Since there's only one such call, this seems like the
least-magical way of doing it.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
The p5302 script runs "index-pack --stdin" in each timing test. It does
two things to try to get good timings:
1. we do the repo creation in a separate (non-timed) setup test, so
that our timing is purely the index-pack run
2. we use a separate repo for each test; this is important because the
presence of existing objects in the repo influences the result
(because we'll end up doing collision checks against them)
But this forgets one thing: we generally run each timed test multiple
times to reduce the impact of noise. Which means that repeats of each
test after the first will be subject to the collision slowdown from
point 2, and we'll generally just end up taking the first time anyway.
Instead, let's create the repo in the test (effectively undoing point
1). That does add a constant amount of extra work to each iteration, but
it's quite small compared to the actual effects we're interested in
measuring.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
This patch fixes a quadratic list insertion in rewrite_one() when
pathspec limiting is combined with --parents. What happens is something
like this:
1. We see that some commit X touches the path, so we try to rewrite
its parents.
2. rewrite_one() loops forever, rewriting parents, until it finds a
relevant parent (or hits the root and decides there are none). The
heavy lifting is done by process_parent(), which uses
try_to_simplify_commit() to drop parents.
3. process_parent() puts any intermediate parents into the
&revs->commits list, inserting by commit date as usual.
So if commit X is recent, and then there's a large chunk of history that
doesn't touch the path, we may add a lot of commits to &revs->commits.
And insertion by commit date is O(n) in the worst case, making the whole
thing quadratic.
We tried to deal with this long ago in fce87ae538 (Fix quadratic
performance in rewrite_one., 2008-07-12). In that scheme, we cache the
oldest commit in the list; if the new commit to be added is older, we
can start our linear traversal there. This often works well in practice
because parents are older than their descendants, and thus we tend to
add older and older commits as we traverse.
But this isn't guaranteed, and in fact there's a simple case where it is
not: merges. Imagine we look at the first parent of a merge and see a
very old commit (let's say 3 years old). And on the second parent, as we
go back 3 years in history, we might have many commits. That one
first-parent commit has polluted our oldest-commit cache; it will remain
the oldest while we traverse a huge chunk of history, during which we
have to fall back to the slow, linear method of adding to the list.
Naively, one might imagine that instead of caching the oldest commit,
we'd start at the last-added one. But that just makes some cases faster
while making others slower (and indeed, while it made a real-world test
case much faster, it does quite poorly in the perf test include here).
Fundamentally, these are just heuristics; our worst case is still
quadratic, and some cases will approach that.
Instead, let's use a data structure with better worst-case performance.
Swapping out revs->commits for something else would have repercussions
all over the code base, but we can take advantage of one fact: for the
rewrite_one() case, nobody actually needs to see those commits in
revs->commits until we've finished generating the whole list.
That leaves us with two obvious options:
1. We can generate the list _unordered_, which should be O(n), and
then sort it afterwards, which would be O(n log n) total. This is
"sort-after" below.
2. We can insert the commits into a separate data structure, like a
priority queue. This is "prio-queue" below.
I expected that sort-after would be the fastest (since it saves us the
extra step of copying the items into the linked list), but surprisingly
the prio-queue seems to be a bit faster.
Here are timings for the new p0001.6 for all three techniques across a
few repositories, as compared to master:
master cache-last sort-after prio-queue
--------------------------------------------------------------------------------------------
GIT_PERF_REPO=git.git
0.52(0.50+0.02) 0.53(0.51+0.02) +1.9% 0.37(0.33+0.03) -28.8% 0.37(0.32+0.04) -28.8%
GIT_PERF_REPO=linux.git
20.81(20.74+0.07) 20.31(20.24+0.07) -2.4% 0.94(0.86+0.07) -95.5% 0.91(0.82+0.09) -95.6%
GIT_PERF_REPO=llvm-project.git
83.67(83.57+0.09) 4.23(4.15+0.08) -94.9% 3.21(3.15+0.06) -96.2% 2.98(2.91+0.07) -96.4%
A few items to note:
- the cache-list tweak does improve the bad case for llvm-project.git
that started my digging into this problem. But it performs terribly
on linux.git, barely helping at all.
- the sort-after and prio-queue techniques work well. They approach
the timing for running without --parents at all, which is what you'd
expect (see below for more data).
- prio-queue just barely outperforms sort-after. As I said, I'm not
really sure why this is the case, but it is. You can see it even
more prominently in this real-world case on llvm-project.git:
git rev-list --parents 07ef786652e7 -- llvm/test/CodeGen/Generic/bswap.ll
where prio-queue routinely outperforms sort-after by about 7%. One
guess is that the prio-queue may just be more efficient because it
uses a compact array.
There are three new perf tests:
- "rev-list --parents" gives us a baseline for running with --parents.
This isn't sped up meaningfully here, because the bad case is
triggered only with simplification. But it's good to make sure we
don't screw it up (now, or in the future).
- "rev-list -- dummy" gives us a baseline for just traversing with
pathspec limiting. This gives a lower bound for the next test (and
it's also a good thing for us to be checking in general for
regressions, since we don't seem to have any existing tests).
- "rev-list --parents -- dummy" shows off the problem (and our fix)
Here are the timings for those three on llvm-project.git, before and
after the fix:
Test master prio-queue
------------------------------------------------------------------------------
0001.3: rev-list --parents 2.24(2.12+0.12) 2.22(2.11+0.11) -0.9%
0001.5: rev-list -- dummy 2.89(2.82+0.07) 2.92(2.89+0.03) +1.0%
0001.6: rev-list --parents -- dummy 83.67(83.57+0.09) 2.98(2.91+0.07) -96.4%
Changes in the first two are basically noise, and you can see we
approach our lower bound in the final one.
Note that we can't fully get rid of the list argument from
process_parents(). Other callers do have lists, and it would be hard to
convert them. They also don't seem to have this problem (probably
because they actually remove items from the list as they loop, meaning
it doesn't grow so large in the first place). So this basically just
drops the "cache_ptr" parameter (which was used only by the one caller
we're fixing here) and replaces it with a prio_queue. Callers are free
to use either data structure, depending on what they're prepared to
handle.
Reported-by: Björn Pettersson A <bjorn.a.pettersson@ericsson.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
Since its inception, the perf-lib.sh script has manually handled the
"--tee" option (and other options which imply it, like "--valgrind")
with a cut-and-pasted block from test-lib.sh. That block has grown stale
over the years, and has at least three problems:
1. It uses $SHELL to re-exec the script, whereas the version in
test-lib.sh learned to use $TEST_SHELL_PATH.
2. It does an ad-hoc search of the "$*" string, whereas test-lib.sh
learned to carefully parse the arguments left to right.
3. It never learned about --verbose-log (which also implies --tee),
so it would not trigger for that option.
This last one was especially annoying, because t/perf/run uses the
GIT_TEST_OPTS from your config.mak to run the perf scripts. So if you've
set, say, "-x --verbose-log" there, it will be passed as part of most
perf runs. And while this script doesn't recognize the option, the
test-lib.sh that we source _does_, and the behavior ends up being much
more annoying:
- as the comment at the top of the block says, we have to run this
tee code early, before we start munging variables (it says
GIT_BUILD_DIR, but the problematic variable is actually
GIT_TEST_INSTALLED).
- since we don't recognize --verbose-log, we don't trigger the block.
We go on to munge GIT_TEST_INSTALLED, converting it from a relative
to an absolute path.
- then we source test-lib.sh, which _does_ recognize --verbose-log. It
re-execs the script, which runs again. But this time with an
absolute version of GIT_TEST_INSTALLED.
- As a result, we copy the absolute version of GIT_TEST_INSTALLED into
perf_results_prefix. Instead of writing our results to the expected
"test-results/build_1234abcd.p1234-whatever.times", we instead write
them to "test-results/_full_path_to_repo_t_perf_build_1234...".
The aggregate.perl script doesn't expect this, and so it prints
"<missing>" for each result (even though it spent considerable time
running the tests!).
We can solve all of these in one blow by just deleting our custom
handling, and relying on the inclusion of test-lib.sh to handle --tee,
--verbose-log, etc.
There's one catch, though. We want to handle GIT_TEST_INSTALLED after
we've included test-lib.sh, since we want it un-munged in the re-exec'd
version of the script. But if we want to convert it from a relative
to an absolute path, we must do so before we load test-lib.sh, since it
will change our working directory. So we compute the absolute directory
first, store it away, then include test-lib.sh, and finally assign to
GIT_TEST_INSTALLED as appropriate.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Enabling pack.writebitmaphashcache should always be a performance win.
It costs only 4 bytes per object on disk, and the timings in ae4f07fbcc
(pack-bitmap: implement optional name_hash cache, 2013-12-21) show it
improving fetch and partial-bitmap clone times by 40-50%.
The only reason we didn't enable it by default at the time is that early
versions of JGit's bitmap reader complained about the presence of
optional header bits it didn't understand. But that was changed in
JGit's d2fa3987a (Use bitcheck to check for presence of OPT_FULL option,
2013-10-30), which made it into JGit v3.5.0 in late 2014.
So let's turn this option on by default. It's backwards-compatible with
all versions of Git, and if you are also using JGit on the same
repository, you'd only run into problems using a version that's almost 5
years old.
We'll drop the manual setting from all of our test scripts, including
perf tests. This isn't strictly necessary, but it has two advantages:
1. If the hash-cache ever stops being enabled by default, our perf
regression tests will notice.
2. We can use the modified perf tests to show off the behavior of an
otherwise unconfigured repo, as shown below.
These are the results of a few of a perf tests against linux.git that
showed interesting results. You can see the expected speedup in 5310.4,
which was noted in ae4f07fbcc. Curiously, 5310.8 did not improve (and
actually got slower), despite seeing the opposite in ae4f07fbcc.
I don't have an explanation for that.
The tests from p5311 did not exist back then, but do show improvements
(a smaller pack due to better deltas, which we found in less time).
Test HEAD^ HEAD
-------------------------------------------------------------------------------------
5310.4: simulated fetch 7.39(22.70+0.25) 5.64(11.43+0.22) -23.7%
5310.8: clone (partial bitmap) 18.45(24.83+1.19) 19.94(28.40+1.36) +8.1%
5311.31: server (128 days) 0.41(1.13+0.05) 0.34(0.72+0.02) -17.1%
5311.32: size (128 days) 7.4M 7.0M -4.8%
5311.33: client (128 days) 1.33(1.49+0.06) 1.29(1.37+0.12) -3.0%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Pruning generally has to traverse the whole commit graph in order to
see which objects are reachable. This is the exact problem that
reachability bitmaps were meant to solve, so let's use them (if they're
available, of course).
Here are timings on git.git:
Test HEAD^ HEAD
------------------------------------------------------------------------
5304.6: prune with bitmaps 3.65(3.56+0.09) 1.01(0.92+0.08) -72.3%
And on linux.git:
Test HEAD^ HEAD
--------------------------------------------------------------------------
5304.6: prune with bitmaps 35.05(34.79+0.23) 3.00(2.78+0.21) -91.4%
The tests show a pretty optimal case, as we'll have just repacked and
should have pretty good coverage of all refs with our bitmaps. But
that's actually pretty realistic: normally prune is run via "gc" right
after repacking.
A few notes on the implementation:
- the change is actually in reachable.c, so it would improve
reachability traversals by "reflog expire --stale-fix", as well.
Those aren't performed regularly, though (a normal "git gc" doesn't
use --stale-fix), so they're not really worth measuring. There's a
low chance of regressing that caller, since the use of bitmaps is
totally transparent from the caller's perspective.
- The bitmap case could actually get away without creating a "struct
object", and instead the caller could just look up each object id in
the bitmap result. However, this would be a marginal improvement in
runtime, and it would make the callers much more complicated. They'd
have to handle both the bitmap and non-bitmap cases separately, and
in the case of git-prune, we'd also have to tweak prune_shallow(),
which relies on our SEEN flags.
- Because we do create real object structs, we go through a few
contortions to create ones of the right type. This isn't strictly
necessary (lookup_unknown_object() would suffice), but it's more
memory efficient to use the correct types, since we already know
them.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The general strategy of "git prune" is to do a full reachability walk,
then for each loose object see if we found it in our walk. But if we
don't have any loose objects, we don't need to do the expensive walk in
the first place.
This patch postpones that walk until the first time we need to see its
results.
Note that this is really a specific case of a more general optimization,
which is that we could traverse only far enough to find the object under
consideration (i.e., stop the traversal when we find it, then pick up
again when asked about the next object, etc). That could save us in some
instances from having to do a full walk. But it's actually a bit tricky
to do with our traversal code, and you'd need to do a full walk anyway
if you have even a single unreachable object (which you generally do, if
any objects are actually left after running git-repack).
So in practice this lazy-load of the full walk catches one easy but
common case (i.e., you've just repacked via git-gc, and there's nothing
unreachable).
The perf script is fairly contrived, but it does show off the
improvement:
Test HEAD^ HEAD
-------------------------------------------------------------------------
5304.4: prune with no objects 3.66(3.60+0.05) 0.00(0.00+0.00) -100.0%
and would let us know if we accidentally regress this optimization.
Note also that we need to take special care with prune_shallow(), which
relies on us having performed the traversal. So this optimization can
only kick in for a non-shallow repository. Since this is easy to get
wrong and is not covered by existing tests, let's add an extra test to
t5304 that covers this case explicitly.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Some of the functions in our test library check that they were invoked
properly with conditions like this:
test "$#" = 2 ||
error "bug in the test script: not 2 parameters to test-expect-success"
If this particular condition is triggered, then 'error' will abort the
whole test script with a bold red error message [1] right away.
However, under certain circumstances the test script will be aborted
completely silently, namely if:
- a similar condition in a test helper function like
'test_line_count' is triggered,
- which is invoked from the test script's "main" shell [2],
- and the test script is run manually (i.e. './t1234-foo.sh' as
opposed to 'make t1234-foo.sh' or 'make test') [3]
- and without the '--verbose' option,
because the error message is printed from within 'test_eval_', where
standard output is redirected either to /dev/null or to a log file.
The only indication that something is wrong is that not all tests in
the script are executed and at the end of the test script's output
there is no "# passed all N tests" message, which are subtle and can
easily go unnoticed, as I had to experience myself.
Send these "bug in the test script" error messages directly to the
test scripts standard error and thus to the terminal, so those bugs
will be much harder to overlook. Instead of updating all ~20 such
'error' calls with a redirection, let's add a BUG() function to
'test-lib.sh', wrapping an 'error' call with the proper redirection
and also including the common prefix of those error messages, and
convert all those call sites [4] to use this new BUG() function
instead.
[1] That particular error message from 'test_expect_success' is
printed in color only when running with or without '--verbose';
with '--tee' or '--verbose-log' the error is printed without
color, but it is printed to the terminal nonetheless.
[2] If such a condition is triggered in a subshell of a test, then
'error' won't be able to abort the whole test script, but only the
subshell, which in turn causes the test to fail in the usual way,
indicating loudly and clearly that something is wrong.
[3] Well, 'error' aborts the test script the same way when run
manually or by 'make' or 'prove', but both 'make' and 'prove' pay
attention to the test script's exit status, and even a silently
aborted test script would then trigger those tools' usual
noticable error messages.
[4] Strictly speaking, not all those 'error' calls need that
redirection to send their output to the terminal, see e.g.
'test_expect_success' in the opening example, but I think it's
better to be consistent.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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p3400 makes a copy of the current repository to test git-rebase
performance, and creates new branches in the copy with `git checkout
-b'. If the original repository has branches with the same name as the
script is trying to create, this operation will fail.
This replaces these calls by `git checkout -B' to force the creation and
update of these branches.
Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Update fsck.skipList implementation and documentation.
* ab/fsck-skiplist:
fsck: support comments & empty lines in skipList
fsck: use oidset instead of oid_array for skipList
fsck: use strbuf_getline() to read skiplist file
fsck: add a performance test for skipList
fsck: add a performance test
fsck: document that skipList input must be unabbreviated
fsck: document and test commented & empty line skipList input
fsck: document and test sorted skipList input
fsck tests: add a test for no skipList input
fsck tests: setup of bogus commit object
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Create a performance test to see how the skipList implementation
performs. First we setup N bad commits, then we see how progressively
working our way up to 0..N in increments of 10x does. I.e. the
needle(s) in the haystack get progressively more numerous.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a plain performance test for "fsck". This test will not be used to
/ referred to in any upcoming commit of mine in this series, but
having a simple test for fsck performance is valuable, so let's add it
while we're at it.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
Junio C Hamano
Patrick Steinhardt
Jeff King
Taylor Blau
Colin Stolley
Elijah Newren
Ævar Arnfjörð Bjarmason
SZEDER Gábor
Alban Gruin
René Scharfe