From 73a2bcb0edb9ffb0b007b3546b430e2c6e415eee Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon, 29 Oct 2007 21:18:11 +0100
Subject: [PATCH] sched: keep utime/stime monotonic
keep utime/stime monotonic.
cpustats use utime/stime as a ratio against sum_exec_runtime, as a
consequence it can happen - when the ratio changes faster than time
accumulates - that either can be appear to go backwards.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
fs/proc/array.c | 3 ++-
include/linux/sched.h | 1 +
kernel/fork.c | 1 +
3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 63c95afb561f..d80baaabf835 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -358,7 +358,8 @@ static cputime_t task_utime(struct task_struct *p)
}
utime = (clock_t)temp;
- return clock_t_to_cputime(utime);
+ 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)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3c07d595979f..b0b1fe6e0b17 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1009,6 +1009,7 @@ struct task_struct {
unsigned int rt_priority;
cputime_t utime, stime, utimescaled, stimescaled;
cputime_t gtime;
+ cputime_t prev_utime;
unsigned long nvcsw, nivcsw; /* context switch counts */
struct timespec start_time; /* monotonic time */
struct timespec real_start_time; /* boot based time */
diff --git a/kernel/fork.c b/kernel/fork.c
index ddafdfac9456..a65bfc47177c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1056,6 +1056,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->gtime = cputime_zero;
p->utimescaled = cputime_zero;
p->stimescaled = cputime_zero;
+ p->prev_utime = cputime_zero;
#ifdef CONFIG_TASK_XACCT
p->rchar = 0; /* I/O counter: bytes read */
--
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