Optimize expand_name_field() to speed up V4 index parsing.
- strbuf_remove() in expand_name_field() is not exactly a good fit
for stripping a part at the end, _setlen() would do the same job
and is much cheaper.
- the open-coded loop to find the end of the string in
expand_name_field() can't beat an optimized strlen()
I used p0002-read-cache.sh to generate some performance data:
p0002-read-cache.sh w/100,000 files
Baseline expand_name_field()
---------------------------------------
22.34(0.01+0.12) 21.14(0.03+0.01) -5.4%
p0002-read-cache.sh w/1,000,000 files
Baseline expand_name_field()
-----------------------------------------
306.44(0.04+0.07) 295.42(0.01+0.07) -3.6%
Suggested by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
Signed-off-by: Ben Peart <Ben.Peart@xxxxxxxxxxxxx>
---
read-cache.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/read-cache.c b/read-cache.c
index 7b1354d759..382cc16bdc 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1754,9 +1754,8 @@ static unsigned long expand_name_field(struct strbuf *name, const char *cp_)
if (name->len < len)
die("malformed name field in the index");
- strbuf_remove(name, name->len - len, len);
- for (ep = cp; *ep; ep++)
- ; /* find the end */
+ strbuf_setlen(name, name->len - len);
+ ep = cp + strlen((const char *)cp);
strbuf_add(name, cp, ep - cp);
return (const char *)ep + 1 - cp_;
}
--
2.18.0.windows.1
