sched: Make task->start_time nanoseconds based
Simplify the timespec to nsec/usec conversions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 67678fa..10c6e82 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1367,7 +1367,7 @@
} vtime_snap_whence;
#endif
unsigned long nvcsw, nivcsw; /* context switch counts */
- struct timespec start_time; /* monotonic time */
+ u64 start_time; /* monotonic time in nsec */
u64 real_start_time; /* boot based time in nsec */
/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
unsigned long min_flt, maj_flt;
diff --git a/kernel/acct.c b/kernel/acct.c
index 1be013c..a1844f1 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -458,9 +458,7 @@
acct_t ac;
mm_segment_t fs;
unsigned long flim;
- u64 elapsed;
- u64 run_time;
- struct timespec uptime;
+ u64 elapsed, run_time;
struct tty_struct *tty;
const struct cred *orig_cred;
@@ -484,10 +482,8 @@
strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
/* calculate run_time in nsec*/
- ktime_get_ts(&uptime);
- run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
- run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
- + current->group_leader->start_time.tv_nsec;
+ run_time = ktime_get_ns();
+ run_time -= current->group_leader->start_time;
/* convert nsec -> AHZ */
elapsed = nsec_to_AHZ(run_time);
#if ACCT_VERSION==3
diff --git a/kernel/fork.c b/kernel/fork.c
index a7ab82d..627b7f8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1262,7 +1262,7 @@
posix_cpu_timers_init(p);
- ktime_get_ts(&p->start_time);
+ p->start_time = ktime_get_ns();
p->real_start_time = ktime_get_boot_ns();
p->io_context = NULL;
p->audit_context = NULL;
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index ea6d170..975cb49 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -31,20 +31,19 @@
struct taskstats *stats, struct task_struct *tsk)
{
const struct cred *tcred;
- struct timespec uptime, ts;
cputime_t utime, stime, utimescaled, stimescaled;
- u64 ac_etime;
+ u64 delta;
BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN);
- /* calculate task elapsed time in timespec */
- ktime_get_ts(&uptime);
- ts = timespec_sub(uptime, tsk->start_time);
- /* rebase elapsed time to usec (should never be negative) */
- ac_etime = timespec_to_ns(&ts);
- do_div(ac_etime, NSEC_PER_USEC);
- stats->ac_etime = ac_etime;
- stats->ac_btime = get_seconds() - ts.tv_sec;
+ /* calculate task elapsed time in nsec */
+ delta = ktime_get_ns() - tsk->start_time;
+ /* Convert to micro seconds */
+ do_div(delta, NSEC_PER_USEC);
+ stats->ac_etime = delta;
+ /* Convert to seconds for btime */
+ do_div(delta, USEC_PER_SEC);
+ stats->ac_btime = get_seconds() - delta;
if (thread_group_leader(tsk)) {
stats->ac_exitcode = tsk->exit_code;
if (tsk->flags & PF_FORKNOEXEC)