linux-kernel - [PATCH] fix granularity of task

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Date:	Tue, 10 Nov 2009 14:47:34 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Spencer Candland <spencer@...ehost.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Oleg Nesterov <oleg@...hat.com>, sgruszka@...hat.com
Subject: [PATCH] fix granularity of task_u/stime()

Remove casting to clock_t from task_u/stime(), and keep granularity of
cputime_t over the calculation.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
---
 kernel/sched.c |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 28dd4f4..1632e82 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5171,41 +5171,44 @@ cputime_t task_stime(struct task_struct *p)
 	return p->stime;
 }
 #else
+
+#ifndef nsecs_to_cputime
+# define nsecs_to_cputime(__nsecs) msecs_to_cputime((__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;
 }
-- 
1.6.5.2



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