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

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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>
This commit is contained in:
Hidetoshi Seto
2009-11-26 14:48:30 +09:00
committed by Ingo Molnar
parent 16bc67edeb
commit d180c5bcce
5 changed files with 44 additions and 27 deletions
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7
kernel/exit.c
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@@ -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;