Any updates or thoughts on this one? While the patch has become quite
trivial, it does results in a savings of 5%-15% in index load time.
I thought the compromise of having this test only run when DEBUG is
defined should limit it to developer builds (hopefully everyone
developing on git is running DEBUG builds :)). Since the test is trying
to detect buggy code when writing the index, I thought that was the
right time to test/catch any issues.
I am working on other, more substantial savings for index load times
(stay tuned) but this seemed like a small simple way to help speed
things up.
On 10/24/2017 10:45 AM, Ben Peart wrote:
There is code in post_read_index_from() to detect out of order cache
entries when reading an index file. This order verification adds cost
to read_index_from() that grows with the size of the index.
Put this on-disk data-structure validation code behind an #ifdef DEBUG
so only debug builds have to pay the cost.
The effect can be seen using t/perf/p0002-read-cache.sh:
Test w/git repo HEAD HEAD~1
----------------------------------------------------------------------------
read_cache/discard_cache 1000 times 0.42(0.01+0.09) 0.48(0.01+0.09) +14.3%
read_cache/discard_cache 1000 times 0.41(0.03+0.04) 0.49(0.00+0.10) +19.5%
read_cache/discard_cache 1000 times 0.42(0.03+0.06) 0.49(0.06+0.04) +16.7%
Test w/10K files HEAD HEAD~1
---------------------------------------------------------------------------
read_cache/discard_cache 1000 times 1.58(0.04+0.00) 1.71(0.00+0.07) +8.2%
read_cache/discard_cache 1000 times 1.64(0.01+0.07) 1.76(0.01+0.09) +7.3%
read_cache/discard_cache 1000 times 1.62(0.03+0.04) 1.71(0.00+0.04) +5.6%
Test w/100K files HEAD HEAD~1
-----------------------------------------------------------------------------
read_cache/discard_cache 1000 times 25.85(0.00+0.06) 27.35(0.01+0.06) +5.8%
read_cache/discard_cache 1000 times 25.82(0.01+0.07) 27.25(0.01+0.07) +5.5%
read_cache/discard_cache 1000 times 26.00(0.01+0.07) 27.36(0.06+0.03) +5.2%
Test with 1,000K files HEAD HEAD~1
-------------------------------------------------------------------------------
read_cache/discard_cache 1000 times 200.61(0.01+0.07) 218.23(0.03+0.06) +8.8%
read_cache/discard_cache 1000 times 201.62(0.03+0.06) 217.86(0.03+0.06) +8.1%
read_cache/discard_cache 1000 times 201.64(0.01+0.09) 217.89(0.03+0.07) +8.1%
Signed-off-by: Ben Peart <benpeart@xxxxxxxxxxxxx>
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
Notes:
Base Ref: master
Web-Diff: https://github.com/benpeart/git/commit/95e20f17ff
Checkout: git fetch https://github.com/benpeart/git no_ce_order-v2 && git checkout 95e20f17ff
### Interdiff (v1..v2):
### Patches
read-cache.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/read-cache.c b/read-cache.c
index 65f4fe8375..fc90ec0fce 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1664,6 +1664,7 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
return ce;
}
+#ifdef DEBUG
static void check_ce_order(struct index_state *istate)
{
unsigned int i;
@@ -1685,6 +1686,7 @@ static void check_ce_order(struct index_state *istate)
}
}
}
+#endif
static void tweak_untracked_cache(struct index_state *istate)
{
@@ -1720,7 +1722,9 @@ static void tweak_split_index(struct index_state *istate)
static void post_read_index_from(struct index_state *istate)
{
+#ifdef DEBUG
check_ce_order(istate);
+#endif
tweak_untracked_cache(istate);
tweak_split_index(istate);
}
base-commit: c52ca88430e6ec7c834af38720295070d8a1e330
