[PATCH 0/4] Fix periodic itimers precision -v4

[PATCH 0/4] Fix periodic itimers precision -v4

[Stanislaw Gruszka]

Hello,

I'm resending patches for fixing itimers periodic ticks precision,
for reference see: http://lkml.org/lkml/2009/4/2/230

Changelog:

v3 -> v4
- Rebase for 2.6.31

v2 -> v3 (resend 5):
- Use CPUCLOCK_PROF CPUCLOCK_VIRT defines in kernel/fork.c
- Using inline function cputime_sub_ns() with sanity check against negative
  results instead of macro.
- Add patch which optimize jiffies_to_cputime(1) for PowerPC with
  CONFIG_VIRT_CPU_ACCOUNTING 

v1 -> v2 (resend 4):
- Add comment about CPUCLOCK_PROF and CPUCLOCK_VIRT are 0 and 1 respectively and
  can be used for indexing itimers array.
- Remove not needed BUG().
- Coding style fixes.
- Better algorithm (idea form Thomas) to calculate next signal time for periodic
  itimers,  we use now precomputed nanosecond value of cputime 1 tick.
- Add patch with simplify arm_timer() function.

v0 -> v1 (resend 3):
- Fix bug: using utime instead of sum stime + utime when setup PROF itimer.
- Fix bug: using value->it_interval instead of ovalue->it_interavl.
- No new definitions IT_PROF and IT_VIRT only CPUCLOCK_PROF and CPUCLOCK_VIRT
  are used.

Cheers
Stanislaw

[PATCH 1/4] itimers: merge ITIMER_VIRT and ITIMER_PROF

[Stanislaw Gruszka]

Both cpu itimers have same data flow in the few places, this patch make
unification of code related with VIRT and PROF itimers.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
 include/linux/sched.h     |   14 ++++-
 kernel/fork.c             |    9 ++-
 kernel/itimer.c           |  146 +++++++++++++++++++++------------------------
 kernel/posix-cpu-timers.c |   98 ++++++++++++++----------------
 4 files changed, 130 insertions(+), 137 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3ab08e4..3b3efad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -470,6 +470,11 @@ struct pacct_struct {
 	unsigned long		ac_minflt, ac_majflt;
 };
 
+struct cpu_itimer {
+	cputime_t expires;
+	cputime_t incr;
+};
+
 /**
  * struct task_cputime - collected CPU time counts
  * @utime:		time spent in user mode, in &cputime_t units
@@ -564,9 +569,12 @@ struct signal_struct {
 	struct pid *leader_pid;
 	ktime_t it_real_incr;
 
-	/* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
-	cputime_t it_prof_expires, it_virt_expires;
-	cputime_t it_prof_incr, it_virt_incr;
+	/*
+	 * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
+	 * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
+	 * values are defined to 0 and 1 respectively
+	 */
+	struct cpu_itimer it[2];
 
 	/*
 	 * Thread group totals for process CPU timers.
diff --git a/kernel/fork.c b/kernel/fork.c
index 9b42695..b794ba3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -62,6 +62,7 @@
 #include <linux/fs_struct.h>
 #include <linux/magic.h>
 #include <linux/perf_counter.h>
+#include <linux/posix-timers.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -789,10 +790,10 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
 	thread_group_cputime_init(sig);
 
 	/* Expiration times and increments. */
-	sig->it_virt_expires = cputime_zero;
-	sig->it_virt_incr = cputime_zero;
-	sig->it_prof_expires = cputime_zero;
-	sig->it_prof_incr = cputime_zero;
+	sig->it[CPUCLOCK_PROF].expires = cputime_zero;
+	sig->it[CPUCLOCK_PROF].incr = cputime_zero;
+	sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
+	sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
 
 	/* Cached expiration times. */
 	sig->cputime_expires.prof_exp = cputime_zero;
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 58762f7..852c88d 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -41,10 +41,43 @@ static struct timeval itimer_get_remtime(struct hrtimer *timer)
 	return ktime_to_timeval(rem);
 }
 
+static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   struct itimerval *value)
+{
+	cputime_t cval, cinterval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	cval = it->expires;
+	cinterval = it->incr;
+	if (!cputime_eq(cval, cputime_zero)) {
+		struct task_cputime cputime;
+		cputime_t t;
+
+		thread_group_cputimer(tsk, &cputime);
+		if (clock_id == CPUCLOCK_PROF)
+			t = cputime_add(cputime.utime, cputime.stime);
+		else
+			/* CPUCLOCK_VIRT */
+			t = cputime.utime;
+
+		if (cputime_le(cval, t))
+			/* about to fire */
+			cval = jiffies_to_cputime(1);
+		else
+			cval = cputime_sub(cval, t);
+	}
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	cputime_to_timeval(cval, &value->it_value);
+	cputime_to_timeval(cinterval, &value->it_interval);
+}
+
 int do_getitimer(int which, struct itimerval *value)
 {
 	struct task_struct *tsk = current;
-	cputime_t cinterval, cval;
 
 	switch (which) {
 	case ITIMER_REAL:
@@ -55,44 +88,10 @@ int do_getitimer(int which, struct itimerval *value)
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_virt_expires;
-		cinterval = tsk->signal->it_virt_incr;
-		if (!cputime_eq(cval, cputime_zero)) {
-			struct task_cputime cputime;
-			cputime_t utime;
-
-			thread_group_cputimer(tsk, &cputime);
-			utime = cputime.utime;
-			if (cputime_le(cval, utime)) { /* about to fire */
-				cval = jiffies_to_cputime(1);
-			} else {
-				cval = cputime_sub(cval, utime);
-			}
-		}
-		spin_unlock_irq(&tsk->sighand->siglock);
-		cputime_to_timeval(cval, &value->it_value);
-		cputime_to_timeval(cinterval, &value->it_interval);
+		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
 		break;
 	case ITIMER_PROF:
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_prof_expires;
-		cinterval = tsk->signal->it_prof_incr;
-		if (!cputime_eq(cval, cputime_zero)) {
-			struct task_cputime times;
-			cputime_t ptime;
-
-			thread_group_cputimer(tsk, &times);
-			ptime = cputime_add(times.utime, times.stime);
-			if (cputime_le(cval, ptime)) { /* about to fire */
-				cval = jiffies_to_cputime(1);
-			} else {
-				cval = cputime_sub(cval, ptime);
-			}
-		}
-		spin_unlock_irq(&tsk->sighand->siglock);
-		cputime_to_timeval(cval, &value->it_value);
-		cputime_to_timeval(cinterval, &value->it_interval);
+		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
 		break;
 	default:
 		return(-EINVAL);
@@ -128,6 +127,36 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   struct itimerval *value, struct itimerval *ovalue)
+{
+	cputime_t cval, cinterval, nval, ninterval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	nval = timeval_to_cputime(&value->it_value);
+	ninterval = timeval_to_cputime(&value->it_interval);
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	cval = it->expires;
+	cinterval = it->incr;
+	if (!cputime_eq(cval, cputime_zero) ||
+	    !cputime_eq(nval, cputime_zero)) {
+		if (cputime_gt(nval, cputime_zero))
+			nval = cputime_add(nval, jiffies_to_cputime(1));
+		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
+	}
+	it->expires = nval;
+	it->incr = ninterval;
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	if (ovalue) {
+		cputime_to_timeval(cval, &ovalue->it_value);
+		cputime_to_timeval(cinterval, &ovalue->it_interval);
+	}
+}
+
 /*
  * Returns true if the timeval is in canonical form
  */
@@ -139,7 +168,6 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 	struct task_struct *tsk = current;
 	struct hrtimer *timer;
 	ktime_t expires;
-	cputime_t cval, cinterval, nval, ninterval;
 
 	/*
 	 * Validate the timevals in value.
@@ -174,48 +202,10 @@ again:
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
-		nval = timeval_to_cputime(&value->it_value);
-		ninterval = timeval_to_cputime(&value->it_interval);
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_virt_expires;
-		cinterval = tsk->signal->it_virt_incr;
-		if (!cputime_eq(cval, cputime_zero) ||
-		    !cputime_eq(nval, cputime_zero)) {
-			if (cputime_gt(nval, cputime_zero))
-				nval = cputime_add(nval,
-						   jiffies_to_cputime(1));
-			set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
-					      &nval, &cval);
-		}
-		tsk->signal->it_virt_expires = nval;
-		tsk->signal->it_virt_incr = ninterval;
-		spin_unlock_irq(&tsk->sighand->siglock);
-		if (ovalue) {
-			cputime_to_timeval(cval, &ovalue->it_value);
-			cputime_to_timeval(cinterval, &ovalue->it_interval);
-		}
+		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 		break;
 	case ITIMER_PROF:
-		nval = timeval_to_cputime(&value->it_value);
-		ninterval = timeval_to_cputime(&value->it_interval);
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_prof_expires;
-		cinterval = tsk->signal->it_prof_incr;
-		if (!cputime_eq(cval, cputime_zero) ||
-		    !cputime_eq(nval, cputime_zero)) {
-			if (cputime_gt(nval, cputime_zero))
-				nval = cputime_add(nval,
-						   jiffies_to_cputime(1));
-			set_process_cpu_timer(tsk, CPUCLOCK_PROF,
-					      &nval, &cval);
-		}
-		tsk->signal->it_prof_expires = nval;
-		tsk->signal->it_prof_incr = ninterval;
-		spin_unlock_irq(&tsk->sighand->siglock);
-		if (ovalue) {
-			cputime_to_timeval(cval, &ovalue->it_value);
-			cputime_to_timeval(cinterval, &ovalue->it_interval);
-		}
+		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 		break;
 	default:
 		return -EINVAL;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index bece7c0..9b2d5e4 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -14,11 +14,11 @@
  */
 void update_rlimit_cpu(unsigned long rlim_new)
 {
-	cputime_t cputime;
+	cputime_t cputime = secs_to_cputime(rlim_new);
+	struct signal_struct *const sig = current->signal;
 
-	cputime = secs_to_cputime(rlim_new);
-	if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
-	    cputime_gt(current->signal->it_prof_expires, cputime)) {
+	if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
+	    cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
 		spin_lock_irq(&current->sighand->siglock);
 		set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
 		spin_unlock_irq(&current->sighand->siglock);
@@ -613,6 +613,9 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 				break;
 			}
 		} else {
+			struct signal_struct *const sig = p->signal;
+			union cpu_time_count *exp = &timer->it.cpu.expires;
+
 			/*
 			 * For a process timer, set the cached expiration time.
 			 */
@@ -620,30 +623,27 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 			default:
 				BUG();
 			case CPUCLOCK_VIRT:
-				if (!cputime_eq(p->signal->it_virt_expires,
+				if (!cputime_eq(sig->it[CPUCLOCK_VIRT].expires,
 						cputime_zero) &&
-				    cputime_lt(p->signal->it_virt_expires,
-					       timer->it.cpu.expires.cpu))
+				    cputime_lt(sig->it[CPUCLOCK_VIRT].expires,
+					       exp->cpu))
 					break;
-				p->signal->cputime_expires.virt_exp =
-					timer->it.cpu.expires.cpu;
+				sig->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_PROF:
-				if (!cputime_eq(p->signal->it_prof_expires,
+				if (!cputime_eq(sig->it[CPUCLOCK_PROF].expires,
 						cputime_zero) &&
-				    cputime_lt(p->signal->it_prof_expires,
-					       timer->it.cpu.expires.cpu))
+				    cputime_lt(sig->it[CPUCLOCK_PROF].expires,
+					       exp->cpu))
 					break;
-				i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
+				i = sig->rlim[RLIMIT_CPU].rlim_cur;
 				if (i != RLIM_INFINITY &&
-				    i <= cputime_to_secs(timer->it.cpu.expires.cpu))
+				    i <= cputime_to_secs(exp->cpu))
 					break;
-				p->signal->cputime_expires.prof_exp =
-					timer->it.cpu.expires.cpu;
+				sig->cputime_expires.prof_exp = exp->cpu;
 				break;
 			case CPUCLOCK_SCHED:
-				p->signal->cputime_expires.sched_exp =
-					timer->it.cpu.expires.sched;
+				sig->cputime_expires.sched_exp = exp->sched;
 				break;
 			}
 		}
@@ -1070,6 +1070,27 @@ static void stop_process_timers(struct task_struct *tsk)
 	spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+			     cputime_t *expires, cputime_t cur_time, int signo)
+{
+	if (cputime_eq(it->expires, cputime_zero))
+		return;
+
+	if (cputime_ge(cur_time, it->expires)) {
+		it->expires = it->incr;
+		if (!cputime_eq(it->expires, cputime_zero))
+			it->expires = cputime_add(it->expires, cur_time);
+
+		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
+	}
+
+	if (!cputime_eq(it->expires, cputime_zero) &&
+	    (cputime_eq(*expires, cputime_zero) ||
+	     cputime_lt(it->expires, *expires))) {
+		*expires = it->expires;
+	}
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them
  * off the tsk->*_timers list onto the firing list.  Per-thread timers
@@ -1089,10 +1110,10 @@ static void check_process_timers(struct task_struct *tsk,
 	 * Don't sample the current process CPU clocks if there are no timers.
 	 */
 	if (list_empty(&timers[CPUCLOCK_PROF]) &&
-	    cputime_eq(sig->it_prof_expires, cputime_zero) &&
+	    cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
 	    sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
 	    list_empty(&timers[CPUCLOCK_VIRT]) &&
-	    cputime_eq(sig->it_virt_expires, cputime_zero) &&
+	    cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
 	    list_empty(&timers[CPUCLOCK_SCHED])) {
 		stop_process_timers(tsk);
 		return;
@@ -1152,38 +1173,11 @@ static void check_process_timers(struct task_struct *tsk,
 	/*
 	 * Check for the special case process timers.
 	 */
-	if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-		if (cputime_ge(ptime, sig->it_prof_expires)) {
-			/* ITIMER_PROF fires and reloads.  */
-			sig->it_prof_expires = sig->it_prof_incr;
-			if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-				sig->it_prof_expires = cputime_add(
-					sig->it_prof_expires, ptime);
-			}
-			__group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
-		}
-		if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
-		    (cputime_eq(prof_expires, cputime_zero) ||
-		     cputime_lt(sig->it_prof_expires, prof_expires))) {
-			prof_expires = sig->it_prof_expires;
-		}
-	}
-	if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-		if (cputime_ge(utime, sig->it_virt_expires)) {
-			/* ITIMER_VIRTUAL fires and reloads.  */
-			sig->it_virt_expires = sig->it_virt_incr;
-			if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-				sig->it_virt_expires = cputime_add(
-					sig->it_virt_expires, utime);
-			}
-			__group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
-		}
-		if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
-		    (cputime_eq(virt_expires, cputime_zero) ||
-		     cputime_lt(sig->it_virt_expires, virt_expires))) {
-			virt_expires = sig->it_virt_expires;
-		}
-	}
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
+			 SIGPROF);
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
+			 SIGVTALRM);
+
 	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 		unsigned long psecs = cputime_to_secs(ptime);
 		cputime_t x;
-- 
1.6.2.5

[PATCH 2/4] itimers: fix periodic tics precision

[Stanislaw Gruszka]

Measure ITIMER_PROF and ITIMER_VIRT timers interval error between real ticks
and requested by user. Take it into account when scheduling next tick.

This patch introduce possibility where time between two consecutive tics is
smaller then requested interval, it preserve however dependency that n tick
is generated not earlier than n*interval time - counting from the beginning
of periodic signal generation.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
 include/linux/sched.h     |    2 ++
 kernel/itimer.c           |   24 +++++++++++++++++++++---
 kernel/posix-cpu-timers.c |   20 +++++++++++++++++---
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3b3efad..a069e65 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -473,6 +473,8 @@ struct pacct_struct {
 struct cpu_itimer {
 	cputime_t expires;
 	cputime_t incr;
+	u32 error;
+	u32 incr_error;
 };
 
 /**
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 852c88d..21adff7 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -42,7 +42,7 @@ static struct timeval itimer_get_remtime(struct hrtimer *timer)
 }
 
 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
-			   struct itimerval *value)
+			   struct itimerval *const value)
 {
 	cputime_t cval, cinterval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];
@@ -127,14 +127,32 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
+{
+	struct timespec ts;
+	s64 cpu_ns;
+
+	cputime_to_timespec(ct, &ts);
+	cpu_ns = timespec_to_ns(&ts);
+
+	return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
+}
+
 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
-			   struct itimerval *value, struct itimerval *ovalue)
+			   const struct itimerval *const value,
+			   struct itimerval *const ovalue)
 {
-	cputime_t cval, cinterval, nval, ninterval;
+	cputime_t cval, nval, cinterval, ninterval;
+	s64 ns_ninterval, ns_nval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];
 
 	nval = timeval_to_cputime(&value->it_value);
+	ns_nval = timeval_to_ns(&value->it_value);
 	ninterval = timeval_to_cputime(&value->it_interval);
+	ns_ninterval = timeval_to_ns(&value->it_interval);
+
+	it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
+	it->error = cputime_sub_ns(nval, ns_nval);
 
 	spin_lock_irq(&tsk->sighand->siglock);
 
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9b2d5e4..b60d644 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1070,6 +1070,8 @@ static void stop_process_timers(struct task_struct *tsk)
 	spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static u32 onecputick;
+
 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 			     cputime_t *expires, cputime_t cur_time, int signo)
 {
@@ -1077,9 +1079,16 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 		return;
 
 	if (cputime_ge(cur_time, it->expires)) {
-		it->expires = it->incr;
-		if (!cputime_eq(it->expires, cputime_zero))
-			it->expires = cputime_add(it->expires, cur_time);
+		if (!cputime_eq(it->incr, cputime_zero)) {
+			it->expires = cputime_add(it->expires, it->incr);
+			it->error += it->incr_error;
+			if (it->error >= onecputick) {
+				it->expires = cputime_sub(it->expires,
+							jiffies_to_cputime(1));
+				it->error -= onecputick;
+			}
+		} else
+			it->expires = cputime_zero;
 
 		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
 	}
@@ -1696,10 +1705,15 @@ static __init int init_posix_cpu_timers(void)
 		.nsleep = thread_cpu_nsleep,
 		.nsleep_restart = thread_cpu_nsleep_restart,
 	};
+	struct timespec ts;
 
 	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
 	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
+	cputime_to_timespec(jiffies_to_cputime(1), &ts);
+	onecputick = ts.tv_nsec;
+	WARN_ON(ts.tv_sec != 0);
+
 	return 0;
 }
 __initcall(init_posix_cpu_timers);
-- 
1.6.2.5

[PATCH 3/4] itimers: simplify arm_timer() code a bit

[Stanislaw Gruszka]

Don't update values in expiration cache when new ones are equal. Add
expire_le() and expire_gt() helpers to simplify the code.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
 kernel/posix-cpu-timers.c |   44 +++++++++++++++++++++++---------------------
 1 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index b60d644..69c9237 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -541,6 +541,17 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 					     now);
 }
 
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+	return cputime_eq(expires, cputime_zero) ||
+	       cputime_gt(expires, new_exp);
+}
+
+static inline int expires_le(cputime_t expires, cputime_t new_exp)
+{
+	return !cputime_eq(expires, cputime_zero) &&
+	       cputime_le(expires, new_exp);
+}
 /*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
@@ -585,31 +596,26 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 		 */
 
 		if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
+			union cpu_time_count *exp = &nt->expires;
+
 			switch (CPUCLOCK_WHICH(timer->it_clock)) {
 			default:
 				BUG();
 			case CPUCLOCK_PROF:
-				if (cputime_eq(p->cputime_expires.prof_exp,
-					       cputime_zero) ||
-				    cputime_gt(p->cputime_expires.prof_exp,
-					       nt->expires.cpu))
-					p->cputime_expires.prof_exp =
-						nt->expires.cpu;
+				if (expires_gt(p->cputime_expires.prof_exp,
+					       exp->cpu))
+					p->cputime_expires.prof_exp = exp->cpu;
 				break;
 			case CPUCLOCK_VIRT:
-				if (cputime_eq(p->cputime_expires.virt_exp,
-					       cputime_zero) ||
-				    cputime_gt(p->cputime_expires.virt_exp,
-					       nt->expires.cpu))
-					p->cputime_expires.virt_exp =
-						nt->expires.cpu;
+				if (expires_gt(p->cputime_expires.virt_exp,
+					       exp->cpu))
+					p->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_SCHED:
 				if (p->cputime_expires.sched_exp == 0 ||
-				    p->cputime_expires.sched_exp >
-							nt->expires.sched)
+				    p->cputime_expires.sched_exp > exp->sched)
 					p->cputime_expires.sched_exp =
-						nt->expires.sched;
+								exp->sched;
 				break;
 			}
 		} else {
@@ -623,17 +629,13 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 			default:
 				BUG();
 			case CPUCLOCK_VIRT:
-				if (!cputime_eq(sig->it[CPUCLOCK_VIRT].expires,
-						cputime_zero) &&
-				    cputime_lt(sig->it[CPUCLOCK_VIRT].expires,
+				if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
 					       exp->cpu))
 					break;
 				sig->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_PROF:
-				if (!cputime_eq(sig->it[CPUCLOCK_PROF].expires,
-						cputime_zero) &&
-				    cputime_lt(sig->it[CPUCLOCK_PROF].expires,
+				if (expires_le(sig->it[CPUCLOCK_PROF].expires,
 					       exp->cpu))
 					break;
 				i = sig->rlim[RLIMIT_CPU].rlim_cur;
-- 
1.6.2.5

[PATCH 4/4] cputime: optimize jiffies_to_cputime(1)

[Stanislaw Gruszka]

For powerpc with CONFIG_VIRT_CPU_ACCOUNTING jiffies_to_cputime(1) is not
compile time constant and run time calculations are quite expensive. To
optimize we use precomputed value. For all other architectures is is
preprocessor definition.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
 arch/ia64/include/asm/cputime.h    |    1 +
 arch/powerpc/include/asm/cputime.h |   13 +++++++++++++
 arch/powerpc/kernel/time.c         |    4 ++++
 arch/s390/include/asm/cputime.h    |    1 +
 include/asm-generic/cputime.h      |    1 +
 kernel/itimer.c                    |    4 ++--
 kernel/posix-cpu-timers.c          |    6 +++---
 kernel/sched.c                     |    9 ++++-----
 8 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/arch/ia64/include/asm/cputime.h b/arch/ia64/include/asm/cputime.h
index d20b998..7fa8a85 100644
--- a/arch/ia64/include/asm/cputime.h
+++ b/arch/ia64/include/asm/cputime.h
@@ -30,6 +30,7 @@ typedef u64 cputime_t;
 typedef u64 cputime64_t;
 
 #define cputime_zero			((cputime_t)0)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~((cputime_t)0) >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index f42e623..fa19f3f 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -18,6 +18,9 @@
 
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
 #include <asm-generic/cputime.h>
+#ifdef __KERNEL__
+static inline void setup_cputime_one_jiffy(void) { }
+#endif
 #else
 
 #include <linux/types.h>
@@ -49,6 +52,11 @@ typedef u64 cputime64_t;
 #ifdef __KERNEL__
 
 /*
+ * One jiffy in timebase units computed during initialization
+ */
+extern cputime_t cputime_one_jiffy;
+
+/*
  * Convert cputime <-> jiffies
  */
 extern u64 __cputime_jiffies_factor;
@@ -89,6 +97,11 @@ static inline cputime_t jiffies_to_cputime(const unsigned long jif)
 	return ct;
 }
 
+static inline void setup_cputime_one_jiffy(void)
+{
+	cputime_one_jiffy = jiffies_to_cputime(1);
+}
+
 static inline cputime64_t jiffies64_to_cputime64(const u64 jif)
 {
 	cputime_t ct;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index eae4511..211d7b0 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -193,6 +193,8 @@ EXPORT_SYMBOL(__cputime_clockt_factor);
 DEFINE_PER_CPU(unsigned long, cputime_last_delta);
 DEFINE_PER_CPU(unsigned long, cputime_scaled_last_delta);
 
+cputime_t cputime_one_jiffy;
+
 static void calc_cputime_factors(void)
 {
 	struct div_result res;
@@ -500,6 +502,7 @@ static int __init iSeries_tb_recal(void)
 				tb_to_xs = divres.result_low;
 				vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
 				vdso_data->tb_to_xs = tb_to_xs;
+				setup_cputime_one_jiffy();
 			}
 			else {
 				printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
@@ -945,6 +948,7 @@ void __init time_init(void)
 	tb_ticks_per_usec = ppc_tb_freq / 1000000;
 	tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
 	calc_cputime_factors();
+	setup_cputime_one_jiffy();
 
 	/*
 	 * Calculate the length of each tick in ns.  It will not be
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 7a3817a..24b1244 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -42,6 +42,7 @@ __div(unsigned long long n, unsigned int base)
 #endif /* __s390x__ */
 
 #define cputime_zero			(0ULL)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
index 1c1fa42..ca0f239 100644
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -7,6 +7,7 @@
 typedef unsigned long cputime_t;
 
 #define cputime_zero			(0UL)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 21adff7..8078a32 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -64,7 +64,7 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 
 		if (cputime_le(cval, t))
 			/* about to fire */
-			cval = jiffies_to_cputime(1);
+			cval = cputime_one_jiffy;
 		else
 			cval = cputime_sub(cval, t);
 	}
@@ -161,7 +161,7 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 	if (!cputime_eq(cval, cputime_zero) ||
 	    !cputime_eq(nval, cputime_zero)) {
 		if (cputime_gt(nval, cputime_zero))
-			nval = cputime_add(nval, jiffies_to_cputime(1));
+			nval = cputime_add(nval, cputime_one_jiffy);
 		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 	}
 	it->expires = nval;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 69c9237..18bdde6 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1086,7 +1086,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 			it->error += it->incr_error;
 			if (it->error >= onecputick) {
 				it->expires = cputime_sub(it->expires,
-							jiffies_to_cputime(1));
+							  cputime_one_jiffy);
 				it->error -= onecputick;
 			}
 		} else
@@ -1461,7 +1461,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 		if (!cputime_eq(*oldval, cputime_zero)) {
 			if (cputime_le(*oldval, now.cpu)) {
 				/* Just about to fire. */
-				*oldval = jiffies_to_cputime(1);
+				*oldval = cputime_one_jiffy;
 			} else {
 				*oldval = cputime_sub(*oldval, now.cpu);
 			}
@@ -1712,7 +1712,7 @@ static __init int init_posix_cpu_timers(void)
 	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
 	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
-	cputime_to_timespec(jiffies_to_cputime(1), &ts);
+	cputime_to_timespec(cputime_one_jiffy, &ts);
 	onecputick = ts.tv_nsec;
 	WARN_ON(ts.tv_sec != 0);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 1b59e26..8f977d5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5031,17 +5031,16 @@ void account_idle_time(cputime_t cputime)
  */
 void account_process_tick(struct task_struct *p, int user_tick)
 {
-	cputime_t one_jiffy = jiffies_to_cputime(1);
-	cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
+	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
 	struct rq *rq = this_rq();
 
 	if (user_tick)
-		account_user_time(p, one_jiffy, one_jiffy_scaled);
+		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
 	else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
-		account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
+		account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
 				    one_jiffy_scaled);
 	else
-		account_idle_time(one_jiffy);
+		account_idle_time(cputime_one_jiffy);
 }
 
 /*
-- 
1.6.2.5

[tip:timers/posixtimers] itimers: Merge ITIMER_VIRT and ITIMER_PROF

[tip-bot for Stanislaw Gruszka]

Commit-ID:  42c4ab41a176ee784c0f28c0b29025a8fc34f05a
Gitweb:     http://git.kernel.org/tip/42c4ab41a176ee784c0f28c0b29025a8fc34f05a
Author:     Stanislaw Gruszka <sgruszka@redhat.com>
AuthorDate: Wed, 29 Jul 2009 12:15:26 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 3 Aug 2009 14:48:35 +0200

itimers: Merge ITIMER_VIRT and ITIMER_PROF

Both cpu itimers have same data flow in the few places, this
patch make unification of code related with VIRT and PROF
itimers.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-2-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 include/linux/sched.h     |   14 ++++-
 kernel/fork.c             |    9 ++-
 kernel/itimer.c           |  146 +++++++++++++++++++++------------------------
 kernel/posix-cpu-timers.c |   98 ++++++++++++++----------------
 4 files changed, 130 insertions(+), 137 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3ab08e4..3b3efad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -470,6 +470,11 @@ struct pacct_struct {
 	unsigned long		ac_minflt, ac_majflt;
 };
 
+struct cpu_itimer {
+	cputime_t expires;
+	cputime_t incr;
+};
+
 /**
  * struct task_cputime - collected CPU time counts
  * @utime:		time spent in user mode, in &cputime_t units
@@ -564,9 +569,12 @@ struct signal_struct {
 	struct pid *leader_pid;
 	ktime_t it_real_incr;
 
-	/* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
-	cputime_t it_prof_expires, it_virt_expires;
-	cputime_t it_prof_incr, it_virt_incr;
+	/*
+	 * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
+	 * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
+	 * values are defined to 0 and 1 respectively
+	 */
+	struct cpu_itimer it[2];
 
 	/*
 	 * Thread group totals for process CPU timers.
diff --git a/kernel/fork.c b/kernel/fork.c
index 29b532e..893ab0b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -62,6 +62,7 @@
 #include <linux/fs_struct.h>
 #include <linux/magic.h>
 #include <linux/perf_counter.h>
+#include <linux/posix-timers.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -790,10 +791,10 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
 	thread_group_cputime_init(sig);
 
 	/* Expiration times and increments. */
-	sig->it_virt_expires = cputime_zero;
-	sig->it_virt_incr = cputime_zero;
-	sig->it_prof_expires = cputime_zero;
-	sig->it_prof_incr = cputime_zero;
+	sig->it[CPUCLOCK_PROF].expires = cputime_zero;
+	sig->it[CPUCLOCK_PROF].incr = cputime_zero;
+	sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
+	sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
 
 	/* Cached expiration times. */
 	sig->cputime_expires.prof_exp = cputime_zero;
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 58762f7..852c88d 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -41,10 +41,43 @@ static struct timeval itimer_get_remtime(struct hrtimer *timer)
 	return ktime_to_timeval(rem);
 }
 
+static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   struct itimerval *value)
+{
+	cputime_t cval, cinterval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	cval = it->expires;
+	cinterval = it->incr;
+	if (!cputime_eq(cval, cputime_zero)) {
+		struct task_cputime cputime;
+		cputime_t t;
+
+		thread_group_cputimer(tsk, &cputime);
+		if (clock_id == CPUCLOCK_PROF)
+			t = cputime_add(cputime.utime, cputime.stime);
+		else
+			/* CPUCLOCK_VIRT */
+			t = cputime.utime;
+
+		if (cputime_le(cval, t))
+			/* about to fire */
+			cval = jiffies_to_cputime(1);
+		else
+			cval = cputime_sub(cval, t);
+	}
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	cputime_to_timeval(cval, &value->it_value);
+	cputime_to_timeval(cinterval, &value->it_interval);
+}
+
 int do_getitimer(int which, struct itimerval *value)
 {
 	struct task_struct *tsk = current;
-	cputime_t cinterval, cval;
 
 	switch (which) {
 	case ITIMER_REAL:
@@ -55,44 +88,10 @@ int do_getitimer(int which, struct itimerval *value)
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_virt_expires;
-		cinterval = tsk->signal->it_virt_incr;
-		if (!cputime_eq(cval, cputime_zero)) {
-			struct task_cputime cputime;
-			cputime_t utime;
-
-			thread_group_cputimer(tsk, &cputime);
-			utime = cputime.utime;
-			if (cputime_le(cval, utime)) { /* about to fire */
-				cval = jiffies_to_cputime(1);
-			} else {
-				cval = cputime_sub(cval, utime);
-			}
-		}
-		spin_unlock_irq(&tsk->sighand->siglock);
-		cputime_to_timeval(cval, &value->it_value);
-		cputime_to_timeval(cinterval, &value->it_interval);
+		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
 		break;
 	case ITIMER_PROF:
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_prof_expires;
-		cinterval = tsk->signal->it_prof_incr;
-		if (!cputime_eq(cval, cputime_zero)) {
-			struct task_cputime times;
-			cputime_t ptime;
-
-			thread_group_cputimer(tsk, &times);
-			ptime = cputime_add(times.utime, times.stime);
-			if (cputime_le(cval, ptime)) { /* about to fire */
-				cval = jiffies_to_cputime(1);
-			} else {
-				cval = cputime_sub(cval, ptime);
-			}
-		}
-		spin_unlock_irq(&tsk->sighand->siglock);
-		cputime_to_timeval(cval, &value->it_value);
-		cputime_to_timeval(cinterval, &value->it_interval);
+		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
 		break;
 	default:
 		return(-EINVAL);
@@ -128,6 +127,36 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   struct itimerval *value, struct itimerval *ovalue)
+{
+	cputime_t cval, cinterval, nval, ninterval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	nval = timeval_to_cputime(&value->it_value);
+	ninterval = timeval_to_cputime(&value->it_interval);
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	cval = it->expires;
+	cinterval = it->incr;
+	if (!cputime_eq(cval, cputime_zero) ||
+	    !cputime_eq(nval, cputime_zero)) {
+		if (cputime_gt(nval, cputime_zero))
+			nval = cputime_add(nval, jiffies_to_cputime(1));
+		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
+	}
+	it->expires = nval;
+	it->incr = ninterval;
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	if (ovalue) {
+		cputime_to_timeval(cval, &ovalue->it_value);
+		cputime_to_timeval(cinterval, &ovalue->it_interval);
+	}
+}
+
 /*
  * Returns true if the timeval is in canonical form
  */
@@ -139,7 +168,6 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 	struct task_struct *tsk = current;
 	struct hrtimer *timer;
 	ktime_t expires;
-	cputime_t cval, cinterval, nval, ninterval;
 
 	/*
 	 * Validate the timevals in value.
@@ -174,48 +202,10 @@ again:
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
-		nval = timeval_to_cputime(&value->it_value);
-		ninterval = timeval_to_cputime(&value->it_interval);
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_virt_expires;
-		cinterval = tsk->signal->it_virt_incr;
-		if (!cputime_eq(cval, cputime_zero) ||
-		    !cputime_eq(nval, cputime_zero)) {
-			if (cputime_gt(nval, cputime_zero))
-				nval = cputime_add(nval,
-						   jiffies_to_cputime(1));
-			set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
-					      &nval, &cval);
-		}
-		tsk->signal->it_virt_expires = nval;
-		tsk->signal->it_virt_incr = ninterval;
-		spin_unlock_irq(&tsk->sighand->siglock);
-		if (ovalue) {
-			cputime_to_timeval(cval, &ovalue->it_value);
-			cputime_to_timeval(cinterval, &ovalue->it_interval);
-		}
+		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 		break;
 	case ITIMER_PROF:
-		nval = timeval_to_cputime(&value->it_value);
-		ninterval = timeval_to_cputime(&value->it_interval);
-		spin_lock_irq(&tsk->sighand->siglock);
-		cval = tsk->signal->it_prof_expires;
-		cinterval = tsk->signal->it_prof_incr;
-		if (!cputime_eq(cval, cputime_zero) ||
-		    !cputime_eq(nval, cputime_zero)) {
-			if (cputime_gt(nval, cputime_zero))
-				nval = cputime_add(nval,
-						   jiffies_to_cputime(1));
-			set_process_cpu_timer(tsk, CPUCLOCK_PROF,
-					      &nval, &cval);
-		}
-		tsk->signal->it_prof_expires = nval;
-		tsk->signal->it_prof_incr = ninterval;
-		spin_unlock_irq(&tsk->sighand->siglock);
-		if (ovalue) {
-			cputime_to_timeval(cval, &ovalue->it_value);
-			cputime_to_timeval(cinterval, &ovalue->it_interval);
-		}
+		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 		break;
 	default:
 		return -EINVAL;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index bece7c0..9b2d5e4 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -14,11 +14,11 @@
  */
 void update_rlimit_cpu(unsigned long rlim_new)
 {
-	cputime_t cputime;
+	cputime_t cputime = secs_to_cputime(rlim_new);
+	struct signal_struct *const sig = current->signal;
 
-	cputime = secs_to_cputime(rlim_new);
-	if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
-	    cputime_gt(current->signal->it_prof_expires, cputime)) {
+	if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
+	    cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
 		spin_lock_irq(&current->sighand->siglock);
 		set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
 		spin_unlock_irq(&current->sighand->siglock);
@@ -613,6 +613,9 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 				break;
 			}
 		} else {
+			struct signal_struct *const sig = p->signal;
+			union cpu_time_count *exp = &timer->it.cpu.expires;
+
 			/*
 			 * For a process timer, set the cached expiration time.
 			 */
@@ -620,30 +623,27 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 			default:
 				BUG();
 			case CPUCLOCK_VIRT:
-				if (!cputime_eq(p->signal->it_virt_expires,
+				if (!cputime_eq(sig->it[CPUCLOCK_VIRT].expires,
 						cputime_zero) &&
-				    cputime_lt(p->signal->it_virt_expires,
-					       timer->it.cpu.expires.cpu))
+				    cputime_lt(sig->it[CPUCLOCK_VIRT].expires,
+					       exp->cpu))
 					break;
-				p->signal->cputime_expires.virt_exp =
-					timer->it.cpu.expires.cpu;
+				sig->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_PROF:
-				if (!cputime_eq(p->signal->it_prof_expires,
+				if (!cputime_eq(sig->it[CPUCLOCK_PROF].expires,
 						cputime_zero) &&
-				    cputime_lt(p->signal->it_prof_expires,
-					       timer->it.cpu.expires.cpu))
+				    cputime_lt(sig->it[CPUCLOCK_PROF].expires,
+					       exp->cpu))
 					break;
-				i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
+				i = sig->rlim[RLIMIT_CPU].rlim_cur;
 				if (i != RLIM_INFINITY &&
-				    i <= cputime_to_secs(timer->it.cpu.expires.cpu))
+				    i <= cputime_to_secs(exp->cpu))
 					break;
-				p->signal->cputime_expires.prof_exp =
-					timer->it.cpu.expires.cpu;
+				sig->cputime_expires.prof_exp = exp->cpu;
 				break;
 			case CPUCLOCK_SCHED:
-				p->signal->cputime_expires.sched_exp =
-					timer->it.cpu.expires.sched;
+				sig->cputime_expires.sched_exp = exp->sched;
 				break;
 			}
 		}
@@ -1070,6 +1070,27 @@ static void stop_process_timers(struct task_struct *tsk)
 	spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+			     cputime_t *expires, cputime_t cur_time, int signo)
+{
+	if (cputime_eq(it->expires, cputime_zero))
+		return;
+
+	if (cputime_ge(cur_time, it->expires)) {
+		it->expires = it->incr;
+		if (!cputime_eq(it->expires, cputime_zero))
+			it->expires = cputime_add(it->expires, cur_time);
+
+		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
+	}
+
+	if (!cputime_eq(it->expires, cputime_zero) &&
+	    (cputime_eq(*expires, cputime_zero) ||
+	     cputime_lt(it->expires, *expires))) {
+		*expires = it->expires;
+	}
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them
  * off the tsk->*_timers list onto the firing list.  Per-thread timers
@@ -1089,10 +1110,10 @@ static void check_process_timers(struct task_struct *tsk,
 	 * Don't sample the current process CPU clocks if there are no timers.
 	 */
 	if (list_empty(&timers[CPUCLOCK_PROF]) &&
-	    cputime_eq(sig->it_prof_expires, cputime_zero) &&
+	    cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
 	    sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
 	    list_empty(&timers[CPUCLOCK_VIRT]) &&
-	    cputime_eq(sig->it_virt_expires, cputime_zero) &&
+	    cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
 	    list_empty(&timers[CPUCLOCK_SCHED])) {
 		stop_process_timers(tsk);
 		return;
@@ -1152,38 +1173,11 @@ static void check_process_timers(struct task_struct *tsk,
 	/*
 	 * Check for the special case process timers.
 	 */
-	if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-		if (cputime_ge(ptime, sig->it_prof_expires)) {
-			/* ITIMER_PROF fires and reloads.  */
-			sig->it_prof_expires = sig->it_prof_incr;
-			if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-				sig->it_prof_expires = cputime_add(
-					sig->it_prof_expires, ptime);
-			}
-			__group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
-		}
-		if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
-		    (cputime_eq(prof_expires, cputime_zero) ||
-		     cputime_lt(sig->it_prof_expires, prof_expires))) {
-			prof_expires = sig->it_prof_expires;
-		}
-	}
-	if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-		if (cputime_ge(utime, sig->it_virt_expires)) {
-			/* ITIMER_VIRTUAL fires and reloads.  */
-			sig->it_virt_expires = sig->it_virt_incr;
-			if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-				sig->it_virt_expires = cputime_add(
-					sig->it_virt_expires, utime);
-			}
-			__group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
-		}
-		if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
-		    (cputime_eq(virt_expires, cputime_zero) ||
-		     cputime_lt(sig->it_virt_expires, virt_expires))) {
-			virt_expires = sig->it_virt_expires;
-		}
-	}
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
+			 SIGPROF);
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
+			 SIGVTALRM);
+
 	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 		unsigned long psecs = cputime_to_secs(ptime);
 		cputime_t x;

[tip:timers/posixtimers] itimers: Fix periodic tics precision

[tip-bot for Stanislaw Gruszka]

Commit-ID:  8356b5f9c424e5831715abbce747197c30d1fd71
Gitweb:     http://git.kernel.org/tip/8356b5f9c424e5831715abbce747197c30d1fd71
Author:     Stanislaw Gruszka <sgruszka@redhat.com>
AuthorDate: Wed, 29 Jul 2009 12:15:27 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 3 Aug 2009 14:48:35 +0200

itimers: Fix periodic tics precision

Measure ITIMER_PROF and ITIMER_VIRT timers interval error
between real ticks and requested by user. Take it into account
when scheduling next tick.

This patch introduce possibility where time between two
consecutive tics is smaller then requested interval, it
preserve however dependency that n tick is generated not
earlier than n*interval time - counting from the beginning of
periodic signal generation.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-3-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 include/linux/sched.h     |    2 ++
 kernel/itimer.c           |   24 +++++++++++++++++++++---
 kernel/posix-cpu-timers.c |   20 +++++++++++++++++---
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3b3efad..a069e65 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -473,6 +473,8 @@ struct pacct_struct {
 struct cpu_itimer {
 	cputime_t expires;
 	cputime_t incr;
+	u32 error;
+	u32 incr_error;
 };
 
 /**
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 852c88d..21adff7 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -42,7 +42,7 @@ static struct timeval itimer_get_remtime(struct hrtimer *timer)
 }
 
 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
-			   struct itimerval *value)
+			   struct itimerval *const value)
 {
 	cputime_t cval, cinterval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];
@@ -127,14 +127,32 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
+{
+	struct timespec ts;
+	s64 cpu_ns;
+
+	cputime_to_timespec(ct, &ts);
+	cpu_ns = timespec_to_ns(&ts);
+
+	return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
+}
+
 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
-			   struct itimerval *value, struct itimerval *ovalue)
+			   const struct itimerval *const value,
+			   struct itimerval *const ovalue)
 {
-	cputime_t cval, cinterval, nval, ninterval;
+	cputime_t cval, nval, cinterval, ninterval;
+	s64 ns_ninterval, ns_nval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];
 
 	nval = timeval_to_cputime(&value->it_value);
+	ns_nval = timeval_to_ns(&value->it_value);
 	ninterval = timeval_to_cputime(&value->it_interval);
+	ns_ninterval = timeval_to_ns(&value->it_interval);
+
+	it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
+	it->error = cputime_sub_ns(nval, ns_nval);
 
 	spin_lock_irq(&tsk->sighand->siglock);
 
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9b2d5e4..b60d644 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1070,6 +1070,8 @@ static void stop_process_timers(struct task_struct *tsk)
 	spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static u32 onecputick;
+
 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 			     cputime_t *expires, cputime_t cur_time, int signo)
 {
@@ -1077,9 +1079,16 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 		return;
 
 	if (cputime_ge(cur_time, it->expires)) {
-		it->expires = it->incr;
-		if (!cputime_eq(it->expires, cputime_zero))
-			it->expires = cputime_add(it->expires, cur_time);
+		if (!cputime_eq(it->incr, cputime_zero)) {
+			it->expires = cputime_add(it->expires, it->incr);
+			it->error += it->incr_error;
+			if (it->error >= onecputick) {
+				it->expires = cputime_sub(it->expires,
+							jiffies_to_cputime(1));
+				it->error -= onecputick;
+			}
+		} else
+			it->expires = cputime_zero;
 
 		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
 	}
@@ -1696,10 +1705,15 @@ static __init int init_posix_cpu_timers(void)
 		.nsleep = thread_cpu_nsleep,
 		.nsleep_restart = thread_cpu_nsleep_restart,
 	};
+	struct timespec ts;
 
 	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
 	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
+	cputime_to_timespec(jiffies_to_cputime(1), &ts);
+	onecputick = ts.tv_nsec;
+	WARN_ON(ts.tv_sec != 0);
+
 	return 0;
 }
 __initcall(init_posix_cpu_timers);

[tip:timers/posixtimers] itimers: Simplify arm_timer() code a bit

[tip-bot for Stanislaw Gruszka]

Commit-ID:  d1e3b6d195770bd422e3229b88edfc154b6a27dd
Gitweb:     http://git.kernel.org/tip/d1e3b6d195770bd422e3229b88edfc154b6a27dd
Author:     Stanislaw Gruszka <sgruszka@redhat.com>
AuthorDate: Wed, 29 Jul 2009 12:15:28 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 3 Aug 2009 14:48:36 +0200

itimers: Simplify arm_timer() code a bit

Don't update values in expiration cache when new ones are
equal. Add expire_le() and expire_gt() helpers to simplify the
code.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-4-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 kernel/posix-cpu-timers.c |   44 +++++++++++++++++++++++---------------------
 1 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index b60d644..69c9237 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -541,6 +541,17 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 					     now);
 }
 
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+	return cputime_eq(expires, cputime_zero) ||
+	       cputime_gt(expires, new_exp);
+}
+
+static inline int expires_le(cputime_t expires, cputime_t new_exp)
+{
+	return !cputime_eq(expires, cputime_zero) &&
+	       cputime_le(expires, new_exp);
+}
 /*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
@@ -585,31 +596,26 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 		 */
 
 		if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
+			union cpu_time_count *exp = &nt->expires;
+
 			switch (CPUCLOCK_WHICH(timer->it_clock)) {
 			default:
 				BUG();
 			case CPUCLOCK_PROF:
-				if (cputime_eq(p->cputime_expires.prof_exp,
-					       cputime_zero) ||
-				    cputime_gt(p->cputime_expires.prof_exp,
-					       nt->expires.cpu))
-					p->cputime_expires.prof_exp =
-						nt->expires.cpu;
+				if (expires_gt(p->cputime_expires.prof_exp,
+					       exp->cpu))
+					p->cputime_expires.prof_exp = exp->cpu;
 				break;
 			case CPUCLOCK_VIRT:
-				if (cputime_eq(p->cputime_expires.virt_exp,
-					       cputime_zero) ||
-				    cputime_gt(p->cputime_expires.virt_exp,
-					       nt->expires.cpu))
-					p->cputime_expires.virt_exp =
-						nt->expires.cpu;
+				if (expires_gt(p->cputime_expires.virt_exp,
+					       exp->cpu))
+					p->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_SCHED:
 				if (p->cputime_expires.sched_exp == 0 ||
-				    p->cputime_expires.sched_exp >
-							nt->expires.sched)
+				    p->cputime_expires.sched_exp > exp->sched)
 					p->cputime_expires.sched_exp =
-						nt->expires.sched;
+								exp->sched;
 				break;
 			}
 		} else {
@@ -623,17 +629,13 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 			default:
 				BUG();
 			case CPUCLOCK_VIRT:
-				if (!cputime_eq(sig->it[CPUCLOCK_VIRT].expires,
-						cputime_zero) &&
-				    cputime_lt(sig->it[CPUCLOCK_VIRT].expires,
+				if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
 					       exp->cpu))
 					break;
 				sig->cputime_expires.virt_exp = exp->cpu;
 				break;
 			case CPUCLOCK_PROF:
-				if (!cputime_eq(sig->it[CPUCLOCK_PROF].expires,
-						cputime_zero) &&
-				    cputime_lt(sig->it[CPUCLOCK_PROF].expires,
+				if (expires_le(sig->it[CPUCLOCK_PROF].expires,
 					       exp->cpu))
 					break;
 				i = sig->rlim[RLIMIT_CPU].rlim_cur;

[tip:timers/posixtimers] cputime: Optimize jiffies_to_cputime(1)

[tip-bot for Stanislaw Gruszka]

Commit-ID:  a42548a18866e87092db93b771e6c5b060d78401
Gitweb:     http://git.kernel.org/tip/a42548a18866e87092db93b771e6c5b060d78401
Author:     Stanislaw Gruszka <sgruszka@redhat.com>
AuthorDate: Wed, 29 Jul 2009 12:15:29 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 3 Aug 2009 14:48:36 +0200

cputime: Optimize jiffies_to_cputime(1)

For powerpc with CONFIG_VIRT_CPU_ACCOUNTING
jiffies_to_cputime(1) is not compile time constant and run time
calculations are quite expensive. To optimize we use
precomputed value. For all other architectures is is
preprocessor definition.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-5-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 arch/ia64/include/asm/cputime.h    |    1 +
 arch/powerpc/include/asm/cputime.h |   13 +++++++++++++
 arch/powerpc/kernel/time.c         |    4 ++++
 arch/s390/include/asm/cputime.h    |    1 +
 include/asm-generic/cputime.h      |    1 +
 kernel/itimer.c                    |    4 ++--
 kernel/posix-cpu-timers.c          |    6 +++---
 kernel/sched.c                     |    9 ++++-----
 8 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/arch/ia64/include/asm/cputime.h b/arch/ia64/include/asm/cputime.h
index d20b998..7fa8a85 100644
--- a/arch/ia64/include/asm/cputime.h
+++ b/arch/ia64/include/asm/cputime.h
@@ -30,6 +30,7 @@ typedef u64 cputime_t;
 typedef u64 cputime64_t;
 
 #define cputime_zero			((cputime_t)0)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~((cputime_t)0) >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index f42e623..fa19f3f 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -18,6 +18,9 @@
 
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
 #include <asm-generic/cputime.h>
+#ifdef __KERNEL__
+static inline void setup_cputime_one_jiffy(void) { }
+#endif
 #else
 
 #include <linux/types.h>
@@ -49,6 +52,11 @@ typedef u64 cputime64_t;
 #ifdef __KERNEL__
 
 /*
+ * One jiffy in timebase units computed during initialization
+ */
+extern cputime_t cputime_one_jiffy;
+
+/*
  * Convert cputime <-> jiffies
  */
 extern u64 __cputime_jiffies_factor;
@@ -89,6 +97,11 @@ static inline cputime_t jiffies_to_cputime(const unsigned long jif)
 	return ct;
 }
 
+static inline void setup_cputime_one_jiffy(void)
+{
+	cputime_one_jiffy = jiffies_to_cputime(1);
+}
+
 static inline cputime64_t jiffies64_to_cputime64(const u64 jif)
 {
 	cputime_t ct;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index eae4511..211d7b0 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -193,6 +193,8 @@ EXPORT_SYMBOL(__cputime_clockt_factor);
 DEFINE_PER_CPU(unsigned long, cputime_last_delta);
 DEFINE_PER_CPU(unsigned long, cputime_scaled_last_delta);
 
+cputime_t cputime_one_jiffy;
+
 static void calc_cputime_factors(void)
 {
 	struct div_result res;
@@ -500,6 +502,7 @@ static int __init iSeries_tb_recal(void)
 				tb_to_xs = divres.result_low;
 				vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
 				vdso_data->tb_to_xs = tb_to_xs;
+				setup_cputime_one_jiffy();
 			}
 			else {
 				printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
@@ -945,6 +948,7 @@ void __init time_init(void)
 	tb_ticks_per_usec = ppc_tb_freq / 1000000;
 	tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
 	calc_cputime_factors();
+	setup_cputime_one_jiffy();
 
 	/*
 	 * Calculate the length of each tick in ns.  It will not be
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 7a3817a..24b1244 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -42,6 +42,7 @@ __div(unsigned long long n, unsigned int base)
 #endif /* __s390x__ */
 
 #define cputime_zero			(0ULL)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
index 1c1fa42..ca0f239 100644
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -7,6 +7,7 @@
 typedef unsigned long cputime_t;
 
 #define cputime_zero			(0UL)
+#define cputime_one_jiffy		jiffies_to_cputime(1)
 #define cputime_max			((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)		((__a) +  (__b))
 #define cputime_sub(__a, __b)		((__a) -  (__b))
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 21adff7..8078a32 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -64,7 +64,7 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 
 		if (cputime_le(cval, t))
 			/* about to fire */
-			cval = jiffies_to_cputime(1);
+			cval = cputime_one_jiffy;
 		else
 			cval = cputime_sub(cval, t);
 	}
@@ -161,7 +161,7 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 	if (!cputime_eq(cval, cputime_zero) ||
 	    !cputime_eq(nval, cputime_zero)) {
 		if (cputime_gt(nval, cputime_zero))
-			nval = cputime_add(nval, jiffies_to_cputime(1));
+			nval = cputime_add(nval, cputime_one_jiffy);
 		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 	}
 	it->expires = nval;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 69c9237..18bdde6 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1086,7 +1086,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 			it->error += it->incr_error;
 			if (it->error >= onecputick) {
 				it->expires = cputime_sub(it->expires,
-							jiffies_to_cputime(1));
+							  cputime_one_jiffy);
 				it->error -= onecputick;
 			}
 		} else
@@ -1461,7 +1461,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 		if (!cputime_eq(*oldval, cputime_zero)) {
 			if (cputime_le(*oldval, now.cpu)) {
 				/* Just about to fire. */
-				*oldval = jiffies_to_cputime(1);
+				*oldval = cputime_one_jiffy;
 			} else {
 				*oldval = cputime_sub(*oldval, now.cpu);
 			}
@@ -1712,7 +1712,7 @@ static __init int init_posix_cpu_timers(void)
 	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
 	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
-	cputime_to_timespec(jiffies_to_cputime(1), &ts);
+	cputime_to_timespec(cputime_one_jiffy, &ts);
 	onecputick = ts.tv_nsec;
 	WARN_ON(ts.tv_sec != 0);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 1b59e26..8f977d5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5031,17 +5031,16 @@ void account_idle_time(cputime_t cputime)
  */
 void account_process_tick(struct task_struct *p, int user_tick)
 {
-	cputime_t one_jiffy = jiffies_to_cputime(1);
-	cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
+	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
 	struct rq *rq = this_rq();
 
 	if (user_tick)
-		account_user_time(p, one_jiffy, one_jiffy_scaled);
+		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
 	else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
-		account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
+		account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
 				    one_jiffy_scaled);
 	else
-		account_idle_time(one_jiffy);
+		account_idle_time(cputime_one_jiffy);
 }
 
 /*