From 711536bd4ba791adfd506583927a8f6c8f821e24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?=
<pclouds@gmail.com>
Date: Tue, 15 Jan 2013 20:35:24 +0700
Subject: [PATCH 1/2] attr: fix off-by-one directory component length
calculation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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94bc671 (Add directory pattern matching to attributes - 2012-12-08)
uses find_basename() to calculate the length of directory part in
prepare_attr_stack. This function expects the directory without the
trailing slash (as "origin" field in match_attr struct is without the
trailing slash). find_basename() includes the trailing slash and
confuses push/pop algorithm.
Consider path = "abc/def" and the push down code:
while (1) {
len = strlen(attr_stack->origin);
if (dirlen <= len)
break;
cp = memchr(path + len + 1, '/', dirlen - len - 1);
if (!cp)
cp = path + dirlen;
dirlen is 4, not 3, without this patch. So when attr_stack->origin is
"abc", it'll miss the exit condition because 4 <= 3 is wrong. It'll
then try to push "abc/" down the attr stack (because "cp" would be
NULL). So we have both "abc" and "abc/" in the stack.
Next time when "abc/ghi" is checked, "abc/" is popped out because of
the off-by-one dirlen, only to be pushed back in again by the above
code. This repeats for all files in the same directory. Which means
at least one failed open syscall per file, or more if .gitattributes
exists.
This is the perf result with 10 runs on git.git:
Test 94bc671^ 94bc671 HEAD
----------------------------------------------------------------------------------------------------------
7810.1: grep worktree, cheap regex 0.02(0.01+0.04) 0.05(0.03+0.05) +150.0% 0.02(0.01+0.04) +0.0%
7810.2: grep worktree, expensive regex 0.25(0.94+0.01) 0.26(0.94+0.02) +4.0% 0.25(0.93+0.02) +0.0%
7810.3: grep --cached, cheap regex 0.11(0.10+0.00) 0.12(0.10+0.02) +9.1% 0.10(0.10+0.00) -9.1%
7810.4: grep --cached, expensive regex 0.61(0.60+0.01) 0.62(0.61+0.01) +1.6% 0.61(0.60+0.00) +0.0%
Reported-by: Ross Lagerwall <rosslagerwall@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
attr.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/attr.c b/attr.c
index 466c93fa509..bb9a470c851 100644
--- a/attr.c
+++ b/attr.c
@@ -583,6 +583,13 @@ static void prepare_attr_stack(const char *path)
dirlen = find_basename(path) - path;
+ /*
+ * find_basename() includes the trailing slash, but we do
+ * _not_ want it.
+ */
+ if (dirlen)
+ dirlen--;
+
/*
* At the bottom of the attribute stack is the built-in
* set of attribute definitions, followed by the contents
From 9db9eecfe5c2490d17c0d4bd5452e4cb1d0948c5 Mon Sep 17 00:00:00 2001
From: Duy Nguyen <pclouds@gmail.com>
Date: Wed, 16 Jan 2013 13:02:38 +0700
Subject: [PATCH 2/2] attr: avoid calling find_basename() twice per path
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
find_basename() is only used inside collect_all_attrs(), called once
in prepare_attr_stack, then again after prepare_attr_stack()
returns. Both calls return exact same value. Reorder the code to do
the same task once. Also avoid strlen() because we knows the length
after finding basename.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
attr.c | 45 ++++++++++++++++++---------------------------
1 file changed, 18 insertions(+), 27 deletions(-)
diff --git a/attr.c b/attr.c
index bb9a470c851..ab2aab28de8 100644
--- a/attr.c
+++ b/attr.c
@@ -564,32 +564,12 @@ static void bootstrap_attr_stack(void)
attr_stack = elem;
}
-static const char *find_basename(const char *path)
-{
- const char *cp, *last_slash = NULL;
-
- for (cp = path; *cp; cp++) {
- if (*cp == '/' && cp[1])
- last_slash = cp;
- }
- return last_slash ? last_slash + 1 : path;
-}
-
-static void prepare_attr_stack(const char *path)
+static void prepare_attr_stack(const char *path, int dirlen)
{
struct attr_stack *elem, *info;
- int dirlen, len;
+ int len;
const char *cp;
- dirlen = find_basename(path) - path;
-
- /*
- * find_basename() includes the trailing slash, but we do
- * _not_ want it.
- */
- if (dirlen)
- dirlen--;
-
/*
* At the bottom of the attribute stack is the built-in
* set of attribute definitions, followed by the contents
@@ -769,15 +749,26 @@ static int macroexpand_one(int attr_nr, int rem)
static void collect_all_attrs(const char *path)
{
struct attr_stack *stk;
- int i, pathlen, rem;
- const char *basename;
+ int i, pathlen, rem, dirlen;
+ const char *basename, *cp, *last_slash = NULL;
- prepare_attr_stack(path);
+ for (cp = path; *cp; cp++) {
+ if (*cp == '/' && cp[1])
+ last_slash = cp;
+ }
+ pathlen = cp - path;
+ if (last_slash) {
+ basename = last_slash + 1;
+ dirlen = last_slash - path;
+ } else {
+ basename = path;
+ dirlen = 0;
+ }
+
+ prepare_attr_stack(path, dirlen);
for (i = 0; i < attr_nr; i++)
check_all_attr[i].value = ATTR__UNKNOWN;
- basename = find_basename(path);
- pathlen = strlen(path);
rem = attr_nr;
for (stk = attr_stack; 0 < rem && stk; stk = stk->prev)
rem = fill(path, pathlen, basename, stk, rem);