latencytop: optimize LT_BACKTRACEDEPTH loops a bit

There is no need to loop any longer when 'same == 0'.

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 10 deletions

diff --git a/kernel/latencytop.c b/kernel/latencytop.c
index b4e3c85abe74..7c74dab0d21b 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 +73,15 @@ 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)
+                        }
+
+                        /* 0 and ULONG_MAX entries mean end of backtrace: */
+                        if (record == 0 || record == ULONG_MAX)
                                 break;
                 }
                 if (same) {
@@ -143,14 +146,18 @@ 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)
+                        }
+
+                        /* 0 and ULONG_MAX entries mean end of backtrace: */
+                        if (record == 0 || record == ULONG_MAX)
                                 break;
                 }
                 if (same) {