On Fri, Mar 14, 2008 at 11:01:35PM +0000, Nix wrote:
> bash-3.2# ./select-sleep 10
> Slept for 13 seconds.
See what kind of difference the patch below makes - it reduces the 30%
oversleeping down to 10% for me. That's still way too much, but it's
better.
The problem being fixed here is that setitimer consistently returns a
remaining time greater than what was originally requested, by ~20%:
1205773032.413780 setitimer(ITIMER_VIRTUAL, {it_interval={0, 10000},
it_value={0, 10000}}, NULL) = 0
1205773032.413814 setitimer(ITIMER_VIRTUAL, {it_interval={0, 0},
it_value={0, 0}}, {it_interval={0, 10998}, it_value={0, 11998}}) = 0
This is setting a 100 HZ timer, immediately followed by a cancellation
which also requests the amount left on the timer. The interval is
rounded up by 10%, and the first tick by 20%.
Jeff
--
Work email - jdike at linux dot intel dot com
Index: linux-2.6.22/arch/um/os-Linux/time.c
===================================================================
--- linux-2.6.22.orig/arch/um/os-Linux/time.c 2008-02-18 11:53:51.000000000
-0500
+++ linux-2.6.22/arch/um/os-Linux/time.c 2008-03-17 12:55:41.000000000
-0400
@@ -58,12 +58,17 @@ static inline long long timeval_to_ns(co
long long disable_timer(void)
{
struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
+ int remain, max = UM_NSEC_PER_SEC / UM_HZ;
if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
printk(UM_KERN_ERR "disable_timer - setitimer failed, "
"errno = %d\n", errno);
- return timeval_to_ns(&time.it_value);
+ remain = timeval_to_ns(&time.it_value);
+ if (remain > max)
+ remain = max;
+
+ return remain;
}
long long os_nsecs(void)
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