From: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Date: Sat, 25 Oct 2008 16:01:21 +0000 (+0100)
Subject: udevd: use a tighter loop for compare_devpath()
X-Git-Tag: 174~1378
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=e25fa4faf5b4977cc90c87003a41107a920bbe4d

udevd: use a tighter loop for compare_devpath()

This crops up in my threaded udevd profiles from time to time.
It's not consistent - probably due to variations in the number
of concurrent events - but it can hit 4% user time and higher.

The change halves the user time spent in compare_devpath().

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
---

diff --git a/udev/udevd.c b/udev/udevd.c
index 21fd6f82e..0bacb3994 100644
--- a/udev/udevd.c
+++ b/udev/udevd.c
@@ -310,26 +310,24 @@ static int mem_size_mb(void)
 
 static int compare_devpath(const char *running, const char *waiting)
 {
-	int i;
+	int i = 0;
 
-	for (i = 0; i < UTIL_PATH_SIZE; i++) {
-		/* identical device event found */
-		if (running[i] == '\0' && waiting[i] == '\0')
-			return 1;
+	while (running[i] == waiting[i] && running[i] != '\0')
+		i++;
 
-		/* parent device event found */
-		if (running[i] == '\0' && waiting[i] == '/')
-			return 2;
+	/* identical device event found */
+	if (running[i] == '\0' && waiting[i] == '\0')
+		return 1;
 
-		/* child device event found */
-		if (running[i] == '/' && waiting[i] == '\0')
-			return 3;
+	/* parent device event found */
+	if (running[i] == '\0' && waiting[i] == '/')
+		return 2;
 
-		/* no matching event */
-		if (running[i] != waiting[i])
-			break;
-	}
+	/* child device event found */
+	if (running[i] == '/' && waiting[i] == '\0')
+		return 3;
 
+	/* no matching event */
 	return 0;
 }