lkml.org 
[lkml]   [2008]   [Jul]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 2/3] sched_clock: record TSC after gtod
To read the gtod we need to grab the xtime lock for read. Reading the gtod
before the TSC can cause a bigger gab if the xtime lock is contended.

This patch simply reverses the order to read the TSC after the gtod.
The locking in the reading of the gtod handles any barriers one might
think is needed.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
kernel/sched_clock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-tip.git/kernel/sched_clock.c
===================================================================
--- linux-tip.git.orig/kernel/sched_clock.c 2008-07-08 11:03:05.000000000 -0400
+++ linux-tip.git/kernel/sched_clock.c 2008-07-08 16:53:34.000000000 -0400
@@ -237,8 +237,8 @@ void sched_clock_tick(void)

WARN_ON_ONCE(!irqs_disabled());

- now = sched_clock();
now_gtod = ktime_to_ns(ktime_get());
+ now = sched_clock();

__raw_spin_lock(&scd->lock);
__update_sched_clock(scd, now, NULL);
--


\
 
 \ /
  Last update: 2008-07-09 06:21    [W:0.079 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site