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| author | Derrick Stolee <dstolee@microsoft.com> | 2021-01-07 16:32:11 (GMT) |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2021-01-16 07:05:13 (GMT) |
| commit | a4b6d202caad83c6dc29abe9b17e53a1b3fb54a0 (patch) | |
| tree | dc54967dc8af006c050712f4071b72e9c05bce39 /cache-tree.c | |
| parent | 0b72536a0b6128d2bfd05d633cd2228d7515b53d (diff) | |
| download | git-a4b6d202caad83c6dc29abe9b17e53a1b3fb54a0.zip git-a4b6d202caad83c6dc29abe9b17e53a1b3fb54a0.tar.gz git-a4b6d202caad83c6dc29abe9b17e53a1b3fb54a0.tar.bz2 | |
cache-tree: speed up consecutive path comparisons
The previous change reduced time spent in strlen() while comparing
consecutive paths in verify_cache(), but we can do better. The
conditional checks the existence of a directory separator at the correct
location, but only after doing a string comparison. Swap the order to be
logically equivalent but perform fewer string comparisons.
To test the effect on performance, I used a repository with over three
million paths in the index. I then ran the following command on repeat:
git -c index.threads=1 commit --amend --allow-empty --no-edit
Here are the measurements over 10 runs after a 5-run warmup:
Benchmark #1: v2.30.0
Time (mean ± σ): 854.5 ms ± 18.2 ms
Range (min … max): 825.0 ms … 892.8 ms
Benchmark #2: Previous change
Time (mean ± σ): 833.2 ms ± 10.3 ms
Range (min … max): 815.8 ms … 849.7 ms
Benchmark #3: This change
Time (mean ± σ): 815.5 ms ± 18.1 ms
Range (min … max): 795.4 ms … 849.5 ms
This change is 2% faster than the previous change and 5% faster than
v2.30.0.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'cache-tree.c')
| -rw-r--r-- | cache-tree.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/cache-tree.c b/cache-tree.c index 4274de7..3f1a8d4 100644 --- a/cache-tree.c +++ b/cache-tree.c @@ -191,8 +191,8 @@ static int verify_cache(struct cache_entry **cache, const char *next_name = next_ce->name; int this_len = ce_namelen(this_ce); if (this_len < ce_namelen(next_ce) && - strncmp(this_name, next_name, this_len) == 0 && - next_name[this_len] == '/') { + next_name[this_len] == '/' && + strncmp(this_name, next_name, this_len) == 0) { if (10 < ++funny) { fprintf(stderr, "...\n"); break; |