Fw: Re: Still seeing decreasing stime/utime
From: Balbir Singh
Date: Thu Aug 28 2008 - 18:52:18 EST
Forgot to cc lkml (the original email did not either, but I need comments on
the patch).
--
Balbir
--- Begin Message ---
* Spencer Candland <spencer@xxxxxxxxxxxx> [2008-08-28 13:56:42]:
> Yes, CONFIG_VIRT_CPU_ACCOUNTING is not enabled, I am seeing this on
> x86/x86_64.
>
> I can not seem to duplicate this when booting with nosmp.
>
Thanks for the config and the update. I ran the same test on a quad
core machine on 2.6.27-rc3 (mmotm a few days old) (x86_64)
50 600
52 658
58 706
62 760
66 810
70 864
72 914
78 964
...
Here is an experimental patch (I've just compiled and booted a machine
with it, I am unable to reproduce your problem), could you please test
it for me and see if it helps solve the problem
Reported-by: spencer@xxxxxxxxxxxx
Spencer Candland reported a problem where utime and stime were going negative
despite the fixes in commit b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa. The
suspected reason for the problem is that signal_struct maintains it's own utime
and stime (of exited tasks), these are not updated using the new task_utime()
routine, hence sig->utime can go backwards and cause the same problem
to occur (sig->utime, adds tsk->utime and not task_utime()). This patch
fixes the problem
TODO: using max(task->prev_utime, derived utime) works for now, but a more
generic solution is to implement cputime_max() and use the cputime_gt()
function for comparison.
Comments? (If the inline functions don't look good, I'll gladly move
the functions over to sched.c)
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
---
fs/proc/array.c | 59 --------------------------------------------------
include/linux/sched.h | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
kernel/exit.c | 6 ++---
3 files changed, 62 insertions(+), 62 deletions(-)
diff -puN kernel/exit.c~fix-utime-stime-moving-backwards kernel/exit.c
--- linux-2.6.27-rc3/kernel/exit.c~fix-utime-stime-moving-backwards 2008-08-29 03:14:57.000000000 +0530
+++ linux-2.6.27-rc3-balbir/kernel/exit.c 2008-08-29 03:21:18.000000000 +0530
@@ -115,9 +115,9 @@ static void __exit_signal(struct task_st
* We won't ever get here for the group leader, since it
* will have been the last reference on the signal_struct.
*/
- sig->utime = cputime_add(sig->utime, tsk->utime);
- sig->stime = cputime_add(sig->stime, tsk->stime);
- sig->gtime = cputime_add(sig->gtime, tsk->gtime);
+ sig->utime = cputime_add(sig->utime, task_utime(tsk));
+ sig->stime = cputime_add(sig->stime, task_stime(tsk));
+ sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
sig->min_flt += tsk->min_flt;
sig->maj_flt += tsk->maj_flt;
sig->nvcsw += tsk->nvcsw;
diff -puN fs/proc/array.c~fix-utime-stime-moving-backwards fs/proc/array.c
--- linux-2.6.27-rc3/fs/proc/array.c~fix-utime-stime-moving-backwards 2008-08-29 03:14:58.000000000 +0530
+++ linux-2.6.27-rc3-balbir/fs/proc/array.c 2008-08-29 03:16:09.000000000 +0530
@@ -349,65 +349,6 @@ int proc_pid_status(struct seq_file *m,
return 0;
}
-/*
- * Use precise platform statistics if available:
- */
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING
-static cputime_t task_utime(struct task_struct *p)
-{
- return p->utime;
-}
-
-static cputime_t task_stime(struct task_struct *p)
-{
- 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;
-
- p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
- return p->prev_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));
-
- if (stime >= 0)
- p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
-
- return p->prev_stime;
-}
-#endif
-
-static cputime_t task_gtime(struct task_struct *p)
-{
- return p->gtime;
-}
-
static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task, int whole)
{
diff -puN include/linux/sched.h~fix-utime-stime-moving-backwards include/linux/sched.h
--- linux-2.6.27-rc3/include/linux/sched.h~fix-utime-stime-moving-backwards 2008-08-29 03:14:58.000000000 +0530
+++ linux-2.6.27-rc3-balbir/include/linux/sched.h 2008-08-29 03:49:04.000000000 +0530
@@ -1431,6 +1431,65 @@ static inline void put_task_struct(struc
}
/*
+ * Use precise platform statistics if available:
+ */
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+static inline cputime_t task_utime(struct task_struct *p)
+{
+ return p->utime;
+}
+
+static inline cputime_t task_stime(struct task_struct *p)
+{
+ return p->stime;
+}
+#else
+static inline 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;
+
+ p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
+ return p->prev_utime;
+}
+
+static inline 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));
+
+ if (stime >= 0)
+ p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
+
+ return p->prev_stime;
+}
+#endif
+
+static inline cputime_t task_gtime(struct task_struct *p)
+{
+ return p->gtime;
+}
+
+/*
* Per process flags
*/
#define PF_ALIGNWARN 0x00000001 /* Print alignment warning msgs */
_
--
Balbir
--- End Message ---