From: Jeff Hostetler <jeffh...@microsoft.com>
Teach has_dir_name() to see if the path of the new item
is greater than the last path in the index array before
attempting to search for it.
has_dir_name() is looking for file/directory collisions
in the index and has to consider each sub-directory
prefix in turn. This can cause multiple binary searches
for each path.
During operations like checkout, merge_working_tree()
populates the new index in sorted order, so we expect
to be able to append in many cases.
This commit is part 2 of 2. This commit handles the
additional possible short-cuts as we look at each
sub-directory prefix.
The net-net gains for add_index_entry_with_check() and
both had_dir_name() commits are best seen for very
large repos.
Here are results for a synthetic repo with 4.2M files.
$ GIT_PERF_REPO=~/work/gfw/t/perf/repos/gen-many-files-10.4.3.git/ ./run HEAD~3
HEAD ./p0006-read-tree-checkout.sh
Test HEAD~3
HEAD
0006.2: read-tree br_base br_ballast (4194305)
29.96(19.26+10.50) 23.76(13.42+10.12) -20.7%
0006.3: switch between br_base br_ballast (4194305)
56.95(36.08+16.83) 45.54(25.94+15.68) -20.0%
0006.4: switch between br_ballast br_ballast_plus_1 (4194305)
90.94(51.50+31.52) 78.22(39.39+30.70) -14.0%
0006.5: switch between aliases (4194305)
93.72(51.63+34.09) 77.94(39.00+30.88) -16.8%
Results for medium repos (like linux.git) are mixed and have
more variance (probably do to disk IO unrelated to this test.
$ GIT_PERF_REPO=/mnt/test/linux.git/ ./run HEAD~3 HEAD
./p0006-read-tree-checkout.sh
Test HEAD~3
HEAD
0006.2: read-tree br_base br_ballast (57994) 0.25(0.21+0.03)
0.20(0.17+0.02) -20.0%
0006.3: switch between br_base br_ballast (57994) 10.67(6.06+2.92)
10.51(5.94+2.91) -1.5%
0006.4: switch between br_ballast br_ballast_plus_1 (57994) 0.59(0.47+0.16)
0.52(0.40+0.13) -11.9%
0006.5: switch between aliases (57994) 0.59(0.44+0.17)
0.51(0.38+0.14) -13.6%
$ GIT_PERF_REPO=/mnt/test/linux.git/ ./run HEAD~3 HEAD
./p0006-read-tree-checkout.sh
Test HEAD~3
HEAD
0006.2: read-tree br_base br_ballast (57994) 0.24(0.21+0.02)
0.21(0.18+0.02) -12.5%
0006.3: switch between br_base br_ballast (57994) 10.42(5.98+2.91)
10.66(5.86+3.09) +2.3%
0006.4: switch between br_ballast br_ballast_plus_1 (57994) 0.59(0.49+0.13)
0.53(0.37+0.16) -10.2%
0006.5: switch between aliases (57994) 0.59(0.43+0.17)
0.50(0.37+0.14) -15.3%
Results for smaller repos (like git.git) are not significant.
$ ./run HEAD~3 HEAD ./p0006-read-tree-checkout.sh
Test HEAD~3
HEAD
0006.2: read-tree br_base br_ballast (3043) 0.01(0.00+0.00)
0.01(0.00+0.00) +0.0%
0006.3: switch between br_base br_ballast (3043) 0.31(0.17+0.11)
0.29(0.19+0.08) -6.5%
0006.4: switch between br_ballast br_ballast_plus_1 (3043) 0.03(0.02+0.00)
0.03(0.02+0.00) +0.0%
0006.5: switch between aliases (3043) 0.03(0.02+0.00)
0.03(0.02+0.00) +0.0%
Signed-off-by: Jeff Hostetler <jeffh...@microsoft.com>
---
read-cache.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 62 insertions(+), 1 deletion(-)
diff --git a/read-cache.c b/read-cache.c
index 9af0bd4..c252b6c 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -965,7 +965,7 @@ static int has_dir_name(struct index_state *istate,
}
for (;;) {
- int len;
+ size_t len;
for (;;) {
if (*--slash == '/')
@@ -975,6 +975,67 @@ static int has_dir_name(struct index_state *istate,
}
len = slash - name;
+ if (cmp_last > 0) {
+ /*
+ * (len + 1) is a directory boundary (including
+ * the trailing slash). And since the loop is
+ * decrementing "slash", the first iteration is
+ * the longest directory prefix; subsequent
+ * iterations consider parent directories.
+ */
+
+ if (len + 1 <= len_eq_last) {
+ /*
+ * The directory prefix (including the trailing
+ * slash) also appears as a prefix in the last
+ * entry, so the remainder cannot collide
(because
+ * strcmp said the whole path was greater).
+ *
+ * EQ: last: xxx/A
+ * this: xxx/B
+ *
+ * LT: last: xxx/file_A
+ * this: xxx/file_B
+ */
+ return retval;
+ }
+
+ if (len > len_eq_last) {
+ /*
+ * This part of the directory prefix (excluding
+ * the trailing slash) is longer than the known
+ * equal portions, so this sub-directory cannot
+ * collide with a file.
+ *
+ * GT: last: xxxA
+ * this: xxxB/file
+ */
+ return retval;
+ }
+
+ if (istate->cache_nr > 0 &&
+ ce_namelen(istate->cache[istate->cache_nr - 1])
> len) {
+ /*
+ * The directory prefix lines up with part of
+ * a longer file or directory name, but sorts
+ * after it, so this sub-directory cannot
+ * collide with a file.
+ *
+ * last: xxx/yy-file (because '-' sorts before
'/')
+ * this: xxx/yy/abc
+ */
+ return retval;
+ }
+
+ /*
+ * This is a possible collision. Fall through and
+ * let the regular search code handle it.
+ *
+ * last: xxx
+ * this: xxx/file
+ */
+ }
+
pos = index_name_stage_pos(istate, name, len, stage);
if (pos >= 0) {
/*
--
2.9.3
