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>

5 files changed, 21 insertions, 23 deletions

diff --git a/arch/ia64/include/asm/cputime.h b/arch/ia64/include/asm/cputime.h
index 7fa8a8594660..6073b187528a 100644
--- a/arch/ia64/include/asm/cputime.h
+++ b/arch/ia64/include/asm/cputime.h
@@ -56,10 +56,10 @@ typedef u64 cputime64_t;
 #define jiffies64_to_cputime64(__jif)   ((__jif) * (NSEC_PER_SEC / HZ))
 
 /*
- * Convert cputime <-> milliseconds
+ * Convert cputime <-> microseconds
  */
-#define cputime_to_msecs(__ct)          ((__ct) / NSEC_PER_MSEC)
-#define msecs_to_cputime(__msecs)       ((__msecs) * NSEC_PER_MSEC)
+#define cputime_to_usecs(__ct)          ((__ct) / NSEC_PER_USEC)
+#define usecs_to_cputime(__usecs)       ((__usecs) * NSEC_PER_USEC)
 
 /*
  * Convert cputime <-> seconds
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index 8bdc6a9e5773..1cf20bdfbeca 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -124,23 +124,23 @@ static inline u64 cputime64_to_jiffies64(const cputime_t ct)
 }
 
 /*
- * Convert cputime <-> milliseconds
+ * Convert cputime <-> microseconds
  */
 extern u64 __cputime_msec_factor;
 
-static inline unsigned long cputime_to_msecs(const cputime_t ct)
+static inline unsigned long cputime_to_usecs(const cputime_t ct)
 {
-        return mulhdu(ct, __cputime_msec_factor);
+        return mulhdu(ct, __cputime_msec_factor) * USEC_PER_MSEC;
 }
 
-static inline cputime_t msecs_to_cputime(const unsigned long ms)
+static inline cputime_t usecs_to_cputime(const unsigned long us)
 {
         cputime_t ct;
         unsigned long sec;
 
         /* have to be a little careful about overflow */
-        ct = ms % 1000;
-        sec = ms / 1000;
+        ct = us % 1000000;
+        sec = us / 1000000;
         if (ct) {
                 ct *= tb_ticks_per_sec;
                 do_div(ct, 1000);
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 8b1a52a137c5..40e2ab0fa3f0 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -73,18 +73,18 @@ cputime64_to_jiffies64(cputime64_t cputime)
 }
 
 /*
- * Convert cputime to milliseconds and back.
+ * Convert cputime to microseconds and back.
  */
 static inline unsigned int
-cputime_to_msecs(const cputime_t cputime)
+cputime_to_usecs(const cputime_t cputime)
 {
-        return cputime_div(cputime, 4096000);
+        return cputime_div(cputime, 4096);
 }
 
 static inline cputime_t
-msecs_to_cputime(const unsigned int m)
+usecs_to_cputime(const unsigned int m)
 {
-        return (cputime_t) m * 4096000;
+        return (cputime_t) m * 4096;
 }
 
 /*
diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
index ca0f239f0e13..2bcc5c7c22a6 100644
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -33,10 +33,10 @@ typedef u64 cputime64_t;
 
 
 /*
- * Convert cputime to milliseconds and back.
+ * Convert cputime to microseconds and back.
  */
-#define cputime_to_msecs(__ct)          jiffies_to_msecs(__ct)
-#define msecs_to_cputime(__msecs)       msecs_to_jiffies(__msecs)
+#define cputime_to_usecs(__ct)          jiffies_to_usecs(__ct);
+#define usecs_to_cputime(__msecs)       usecs_to_jiffies(__msecs);
 
 /*
  * Convert cputime to seconds and back.
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;