taskstats: use real microsecond granularity for CPU times

The taskstats interface uses microsecond granularity for the user and
system time values.  The conversion from cputime to the taskstats values
uses the cputime_to_msecs primitive which effectively limits the
granularity to milliseconds.  Add the cputime_to_usecs primitive for
architectures that have better, more precise CPU time values.  Remove
cputime_to_msecs primitive because there are no more users left.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Luck Tony <tony.luck@intel.com>
Cc: Shailabh Nagar <nagar1234@in.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Shailabh Nagar <nagar@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 6 deletions

diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 0a67e041edf8..24dc60d9fa1f 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -63,12 +63,10 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
         stats->ac_ppid   = pid_alive(tsk) ?
                                 rcu_dereference(tsk->real_parent)->tgid : 0;
         rcu_read_unlock();
-        stats->ac_utime  = cputime_to_msecs(tsk->utime) * USEC_PER_MSEC;
-        stats->ac_stime  = cputime_to_msecs(tsk->stime) * USEC_PER_MSEC;
-        stats->ac_utimescaled =
-                cputime_to_msecs(tsk->utimescaled) * USEC_PER_MSEC;
-        stats->ac_stimescaled =
-                cputime_to_msecs(tsk->stimescaled) * USEC_PER_MSEC;
+        stats->ac_utime = cputime_to_usecs(tsk->utime);
+        stats->ac_stime = cputime_to_usecs(tsk->stime);
+        stats->ac_utimescaled = cputime_to_usecs(tsk->utimescaled);
+        stats->ac_stimescaled = cputime_to_usecs(tsk->stimescaled);
         stats->ac_minflt = tsk->min_flt;
         stats->ac_majflt = tsk->maj_flt;