sched: Introduce task_times() to replace task_{u,s}time() pair

Functions task_{u,s}time() are called in pair in almost all
cases.  However task_stime() is implemented to call task_utime()
from its inside, so such paired calls run task_utime() twice.

It means we do heavy divisions (div_u64 + do_div) twice to get
utime and stime which can be obtained at same time by one set
of divisions.

This patch introduces a function task_times(*tsk, *utime,
*stime) to retrieve utime and stime at once in better, optimized
way.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Spencer Candland <spencer@bluehost.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Americo Wang <xiyou.wangcong@gmail.com>
LKML-Reference: <4B0E16AE.906@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index e209f64..330deda 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -535,8 +535,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
        if (!whole) {
                min_flt = task->min_flt;
                maj_flt = task->maj_flt;
-               utime = task_utime(task);
-               stime = task_stime(task);
+               task_times(task, &utime, &stime);
                gtime = task_gtime(task);
        }
 

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 78ba664..fe6ae15 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1723,6 +1723,7 @@ static inline void put_task_struct(struct task_struct *t)
 extern cputime_t task_utime(struct task_struct *p);
 extern cputime_t task_stime(struct task_struct *p);
 extern cputime_t task_gtime(struct task_struct *p);
+extern void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st);
 
 /*
  * Per process flags

diff --git a/kernel/exit.c b/kernel/exit.c
index f7864ac..29068ab 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -91,6 +91,8 @@ static void __exit_signal(struct task_struct *tsk)
        if (atomic_dec_and_test(&sig->count))
                posix_cpu_timers_exit_group(tsk);
        else {
+               cputime_t utime, stime;
+
                /*
                 * If there is any task waiting for the group exit
                 * then notify it:
@@ -110,8 +112,9 @@ static void __exit_signal(struct task_struct *tsk)
                 * 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, task_utime(tsk));
-               sig->stime = cputime_add(sig->stime, task_stime(tsk));
+               task_times(tsk, &utime, &stime);
+               sig->utime = cputime_add(sig->utime, utime);
+               sig->stime = cputime_add(sig->stime, stime);
                sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
                sig->min_flt += tsk->min_flt;
                sig->maj_flt += tsk->maj_flt;

diff --git a/kernel/sched.c b/kernel/sched.c
index 315ba40..475a6f2 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5191,6 +5191,14 @@ cputime_t task_stime(struct task_struct *p)
 {
        return p->stime;
 }
+
+void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
+{
+       if (ut)
+               *ut = task_utime(p);
+       if (st)
+               *st = task_stime(p);
+}
 #else
 
 #ifndef nsecs_to_cputime
@@ -5198,41 +5206,48 @@ cputime_t task_stime(struct task_struct *p)
        msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC))
 #endif
 
-cputime_t task_utime(struct task_struct *p)
+void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 {
-       cputime_t utime = p->utime, total = utime + p->stime;
-       u64 temp;
+       cputime_t rtime, utime = p->utime, total = utime + p->stime;
 
        /*
         * Use CFS's precise accounting:
         */
-       temp = (u64)nsecs_to_cputime(p->se.sum_exec_runtime);
+       rtime = nsecs_to_cputime(p->se.sum_exec_runtime);
 
        if (total) {
-               temp *= utime;
+               u64 temp;
+
+               temp = (u64)(rtime * utime);
                do_div(temp, total);
-       }
-       utime = (cputime_t)temp;
+               utime = (cputime_t)temp;
+       } else
+               utime = rtime;
 
+       /*
+        * Compare with previous values, to keep monotonicity:
+        */
        p->prev_utime = max(p->prev_utime, utime);
-       return p->prev_utime;
+       p->prev_stime = max(p->prev_stime, rtime - p->prev_utime);
+
+       if (ut)
+               *ut = p->prev_utime;
+       if (st)
+               *st = p->prev_stime;
+}
+
+cputime_t task_utime(struct task_struct *p)
+{
+       cputime_t utime;
+       task_times(p, &utime, NULL);
+       return utime;
 }
 
 cputime_t task_stime(struct task_struct *p)
 {
        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 = nsecs_to_cputime(p->se.sum_exec_runtime) - task_utime(p);
-
-       if (stime >= 0)
-               p->prev_stime = max(p->prev_stime, stime);
-
-       return p->prev_stime;
+       task_times(p, NULL, &stime);
+       return stime;
 }
 #endif
 

diff --git a/kernel/sys.c b/kernel/sys.c
index ce17760..bbdfce0 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1346,8 +1346,7 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
        utime = stime = cputime_zero;
 
        if (who == RUSAGE_THREAD) {
-               utime = task_utime(current);
-               stime = task_stime(current);
+               task_times(current, &utime, &stime);
                accumulate_thread_rusage(p, r);
                maxrss = p->signal->maxrss;
                goto out;