Chuck, Balbir,
we still have a problem with stime occosionally going backwards. I stated
below that I think this is not fixable with the current utime/stime split
algorithm.
Balbir, you wrote this code, Chuck you tried to fix it. Any ideas how to
fix this properly? The only idea I have requires that we save the old value
of utime and stime and therefore requires additional locking.
Otherwise I suggest to apply my reversion patch from below:
Am Sonntag, 14. Oktober 2007 schrieb Christian Borntraeger:
--------- patch-----------
Fix stime going backwards
after 2.6.22 the accounting was changes to use sched_clock and to use stime
and utime only for the split. This is where task_utime and task_stime were
introduced. See the code in 2.6.23-rc1.
Unfortunately this broke the accouting on s390 which already has precise
numbers in utime and stime. So the code was partially reverted to use stime
and utime again where appropriate, which are of type cputime_t.
It now seems, that the rest of the logic is still broken.
This patch basically reverts the rest of b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa
and should restore the 2.6.22 behavior. The process time is used from tasks
utime and stime instead of the scheduler clock. That means, in general after
a long period of time, it is less accurate than the sum_exec_runtime based
code, but it doesnt break top.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
fs/proc/array.c | 37 -------------------------------------
1 file changed, 37 deletions(-)
Index: linux-2.6/fs/proc/array.c
===================================================================
--- linux-2.6.orig/fs/proc/array.c
+++ linux-2.6/fs/proc/array.c
@@ -323,7 +323,6 @@ int proc_pid_status(struct task_struct *
/*
* Use precise platform statistics if available:
*/
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING
static cputime_t task_utime(struct task_struct *p)
{
return p->utime;
@@ -333,42 +332,6 @@ static cputime_t task_stime(struct task_
{
return p->stime;
}
-#else
-static cputime_t task_utime(struct task_struct *p)
-{
- clock_t utime = cputime_to_clock_t(p->utime),
- total = utime + cputime_to_clock_t(p->stime);
- u64 temp;
-
- /*
- * Use CFS's precise accounting:
- */
- temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
-
- if (total) {
- temp *= utime;
- do_div(temp, total);
- }
- utime = (clock_t)temp;
-
- return clock_t_to_cputime(utime);
-}
-
-static cputime_t task_stime(struct task_struct *p)
-{
- clock_t stime;
-
- /*
- * Use CFS's precise accounting. (we subtract utime from
- * the total, to make sure the total observed by userspace
- * grows monotonically - apps rely on that):
- */
- stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
- cputime_to_clock_t(task_utime(p));
-
- return clock_t_to_cputime(stime);
-}
-#endif
static int do_task_stat(struct task_struct *task, char *buffer, int whole)
{
-
