Commit-ID: 761b1d26df542fd5eb348837351e4d2f3bc7bffe
Gitweb: http://git.kernel.org/tip/761b1d26df542fd5eb348837351e4d2f3bc7bffe
Author: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
AuthorDate: Thu, 12 Nov 2009 13:33:45 +0900
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 12 Nov 2009 15:23:47 +0100
sched: Fix granularity of task_u/stime()
Originally task_s/utime() were designed to return clock_t but
later changed to return cputime_t by following commit:
commit efe567fc8281661524ffa75477a7c4ca9b466c63
Author: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Date: Thu Aug 23 15:18:02 2007 +0200
It only changed the type of return value, but not the
implementation. As the result the granularity of task_s/utime()
is still that of clock_t, not that of cputime_t.
So using task_s/utime() in __exit_signal() makes values
accumulated to the signal struct to be rounded and coarse
grained.
This patch removes casts to clock_t in task_u/stime(), to keep
granularity of cputime_t over the calculation.
v2:
Use div_u64() to avoid error "undefined reference to `__udivdi3`"
on some 32bit systems.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: xiyou.wangcong@xxxxxxxxx
Cc: Spencer Candland <spencer@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
LKML-Reference: <4AFB9029.9000208@xxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 22 +++++++++++++---------
1 files changed, 13 insertions(+), 9 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 43e61fa..ab9a034 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5156,41 +5156,45 @@ cputime_t task_stime(struct task_struct *p)
return p->stime;
}
#else
+
+#ifndef nsecs_to_cputime
+# define nsecs_to_cputime(__nsecs) \
+ msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC))
+#endif
+
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);
+ cputime_t utime = p->utime, total = utime + p->stime;
u64 temp;
/*
* Use CFS's precise accounting:
*/
- temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
+ temp = (u64)nsecs_to_cputime(p->se.sum_exec_runtime);
if (total) {
temp *= utime;
do_div(temp, total);
}
- utime = (clock_t)temp;
+ utime = (cputime_t)temp;
- p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
+ p->prev_utime = max(p->prev_utime, utime);
return p->prev_utime;
}
cputime_t task_stime(struct task_struct *p)
{
- clock_t stime;
+ cputime_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));
+ stime = nsecs_to_cputime(p->se.sum_exec_runtime) - task_utime(p);
if (stime >= 0)
- p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
+ p->prev_stime = max(p->prev_stime, stime);
return p->prev_stime;
}
--
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