linux-kernel - latencytop: optimize LT_BACKTRACEDEPTH loops a bit

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Date:	Sat, 02 Feb 2008 23:59:31 +0100
From:	Dmitry Adamushko <dmitry.adamushko@...il.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dmitry.adamushko@...il.com
Subject: latencytop: optimize LT_BACKTRACEDEPTH loops a bit

Subject: latencytop: optimize LT_BACKTRACEDEPTH loops a bit.

It looks like there is no need to loop any longer when 'same == 0'.


Signed-off-by: Dmitry Adamushko <dmitry.adamushko@...il.com>


diff --git a/kernel/latencytop.c b/kernel/latencytop.c
index b4e3c85..61f7da0 100644
--- a/kernel/latencytop.c
+++ b/kernel/latencytop.c
@@ -64,8 +64,8 @@ account_global_scheduler_latency(struct task_struct *tsk, struct latency_record
 		return;
 
 	for (i = 0; i < MAXLR; i++) {
-		int q;
-		int same = 1;
+		int q, same = 1;
+
 		/* Nothing stored: */
 		if (!latency_record[i].backtrace[0]) {
 			if (firstnonnull > i)
@@ -73,12 +73,12 @@ account_global_scheduler_latency(struct task_struct *tsk, struct latency_record
 			continue;
 		}
 		for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
-			if (latency_record[i].backtrace[q] !=
-				lat->backtrace[q])
+			unsigned long record = lat->backtrace[q];
+
+			if (latency_record[i].backtrace[q] != record)
 				same = 0;
-			if (same && lat->backtrace[q] == 0)
-				break;
-			if (same && lat->backtrace[q] == ULONG_MAX)
+
+			if (!same || record == 0 || record == ULONG_MAX)
 				break;
 		}
 		if (same) {
@@ -143,14 +143,15 @@ account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
 	for (i = 0; i < LT_SAVECOUNT ; i++) {
 		struct latency_record *mylat;
 		int same = 1;
+
 		mylat = &tsk->latency_record[i];
 		for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
-			if (mylat->backtrace[q] !=
-				lat.backtrace[q])
+			unsigned long record = lat.backtrace[q];
+
+			if (mylat->backtrace[q] != record)
 				same = 0;
-			if (same && lat.backtrace[q] == 0)
-				break;
-			if (same && lat.backtrace[q] == ULONG_MAX)
+
+			if (!same || record == 0 || record == ULONG_MAX)
 				break;
 		}
 		if (same) {


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