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Date: Fri, 25 May 2007 14:46:52 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Galbraith <efault@....de>,
Arjan van de Ven <arjan@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
pranith-kumar_d@...torg.com, Andi Kleen <andi@...stfloor.org>
Subject: Re: [patch] CFS scheduler, -v14
* Ingo Molnar <mingo@...e.hu> wrote:
> btw., CFS does this change to fs/proc/array.c:
>
> @@ -410,6 +408,14 @@ static int do_task_stat(struct task_stru
> /* convert nsec -> ticks */
> start_time = nsec_to_clock_t(start_time);
>
> + /*
> + * Use CFS's precise accounting, if available:
> + */
> + if (!has_rt_policy(task)) {
> + utime = nsec_to_clock_t(task->sum_exec_runtime);
> + stime = 0;
> + }
> +
> res = sprintf(buffer,"%d (%s) %c %d %d %d %d %d %lu %lu \
> %lu %lu %lu %lu %lu %ld %ld %ld %ld %d 0 %llu %lu %ld %lu %lu %lu %lu %lu \
> %lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu %llu\n",
>
> if you have some spare capacity to improve this code, it could be
> further enhanced by not setting 'stime' to zero, but using the
> existing jiffies based utime/stime statistics as a _ratio_ to split up
> the precise p->sum_exec_runtime. That way we dont have to add precise
> accounting to syscall entry/exit points (that would be quite
> expensive), but still the sum of utime+stime would be very precise.
> (and that's what matters most anyway)
i found an accounting bug in this: it didnt sum up threads correctly.
The patch below fixes this. The stime == 0 problem is still there
though.
Ingo
Index: linux/fs/proc/array.c
===================================================================
--- linux.orig/fs/proc/array.c
+++ linux/fs/proc/array.c
@@ -310,6 +310,29 @@ int proc_pid_status(struct task_struct *
return buffer - orig;
}
+static clock_t task_utime(struct task_struct *p)
+{
+ /*
+ * Use CFS's precise accounting, if available:
+ */
+ if (!has_rt_policy(p) && !(sysctl_sched_load_smoothing & 128))
+ return nsec_to_clock_t(p->sum_exec_runtime);
+
+ return cputime_to_clock_t(p->utime);
+}
+
+static clock_t task_stime(struct task_struct *p)
+{
+ /*
+ * Use CFS's precise accounting, if available:
+ */
+ if (!has_rt_policy(p) && !(sysctl_sched_load_smoothing & 128))
+ return 0;
+
+ return cputime_to_clock_t(p->stime);
+}
+
+
static int do_task_stat(struct task_struct *task, char * buffer, int whole)
{
unsigned long vsize, eip, esp, wchan = ~0UL;
@@ -324,7 +347,8 @@ static int do_task_stat(struct task_stru
unsigned long long start_time;
unsigned long cmin_flt = 0, cmaj_flt = 0;
unsigned long min_flt = 0, maj_flt = 0;
- cputime_t cutime, cstime, utime, stime;
+ cputime_t cutime, cstime;
+ clock_t utime, stime;
unsigned long rsslim = 0;
char tcomm[sizeof(task->comm)];
unsigned long flags;
@@ -342,7 +366,8 @@ static int do_task_stat(struct task_stru
sigemptyset(&sigign);
sigemptyset(&sigcatch);
- cutime = cstime = utime = stime = cputime_zero;
+ cutime = cstime = cputime_zero;
+ utime = stime = 0;
rcu_read_lock();
if (lock_task_sighand(task, &flags)) {
@@ -368,15 +393,15 @@ static int do_task_stat(struct task_stru
do {
min_flt += t->min_flt;
maj_flt += t->maj_flt;
- utime = cputime_add(utime, t->utime);
- stime = cputime_add(stime, t->stime);
+ utime += task_utime(t);
+ stime += task_stime(t);
t = next_thread(t);
} while (t != task);
min_flt += sig->min_flt;
maj_flt += sig->maj_flt;
- utime = cputime_add(utime, sig->utime);
- stime = cputime_add(stime, sig->stime);
+ utime += cputime_to_clock_t(sig->utime);
+ stime += cputime_to_clock_t(sig->stime);
}
sid = signal_session(sig);
@@ -392,8 +417,8 @@ static int do_task_stat(struct task_stru
if (!whole) {
min_flt = task->min_flt;
maj_flt = task->maj_flt;
- utime = task->utime;
- stime = task->stime;
+ utime = task_utime(task);
+ stime = task_stime(task);
}
/* scale priority and nice values from timeslices to -20..20 */
@@ -408,14 +433,6 @@ static int do_task_stat(struct task_stru
/* convert nsec -> ticks */
start_time = nsec_to_clock_t(start_time);
- /*
- * Use CFS's precise accounting, if available:
- */
- if (!has_rt_policy(task)) {
- utime = nsec_to_clock_t(task->sum_exec_runtime);
- stime = 0;
- }
-
res = sprintf(buffer,"%d (%s) %c %d %d %d %d %d %lu %lu \
%lu %lu %lu %lu %lu %ld %ld %ld %ld %d 0 %llu %lu %ld %lu %lu %lu %lu %lu \
%lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu %llu\n",
-
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