Re: [PATCH] sched_clock: Provide local_clock() and improve documentation

[Piotr Hosowicz]

On 28.05.2010 15:13, Peter Zijlstra wrote:
> On Thu, 2010-05-27 at 11:33 -0700, Andrew Morton wrote:
>
> > Cool, thanks.  You didn't Cc a mailing list :(
>
> Oops, must have managed to wreck the CC list somewhere, restored LKML.
>
> How does the below look?

Earlier someone (you? I didn't write down) has published such a patch:

f4b87dee9

Index: linux-2.6/arch/parisc/kernel/ftrace.c
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/ftrace.c
+++ linux-2.6/arch/parisc/kernel/ftrace.c
@@ -82,7 +82,7 @@ unsigned long ftrace_return_to_handler(u
 	unsigned long ret;

 	pop_return_trace(&trace, &ret);
-	trace.rettime = cpu_clock(raw_smp_processor_id());
+	trace.rettime = local_clock();
 	ftrace_graph_return(&trace);

 	if (unlikely(!ret)) {
@@ -126,7 +126,7 @@ void prepare_ftrace_return(unsigned long
 		return;
 	}

-	calltime = cpu_clock(raw_smp_processor_id());
+	calltime = local_clock();

 	if (push_return_trace(old, calltime,
 				self_addr, &trace.depth) == -EBUSY) {
Index: linux-2.6/include/linux/blkdev.h
===================================================================
--- linux-2.6.orig/include/linux/blkdev.h
+++ linux-2.6/include/linux/blkdev.h
@@ -1213,12 +1213,12 @@ int kblockd_schedule_work(struct request
 #ifdef CONFIG_BLK_CGROUP
 static inline void set_start_time_ns(struct request *req)
 {
-	req->start_time_ns = sched_clock();
+	req->start_time_ns = local_clock();
 }

 static inline void set_io_start_time_ns(struct request *req)
 {
-	req->io_start_time_ns = sched_clock();
+	req->io_start_time_ns = local_clock();
 }

 static inline uint64_t rq_start_time_ns(struct request *req)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1822,6 +1822,7 @@ extern void sched_clock_idle_wakeup_even
  * clock constructed from sched_clock():
  */
 extern unsigned long long cpu_clock(int cpu);
+extern unsigned long long local_clock(void);

 extern unsigned long long
 task_sched_runtime(struct task_struct *task);
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c
+++ linux-2.6/kernel/lockdep.c
@@ -146,7 +146,7 @@ static DEFINE_PER_CPU(struct lock_class_

 static inline u64 lockstat_clock(void)
 {
-	return cpu_clock(smp_processor_id());
+	return local_clock();
 }

 static int lock_point(unsigned long points[], unsigned long ip)
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -214,7 +214,7 @@ static void perf_unpin_context(struct pe

 static inline u64 perf_clock(void)
 {
-	return cpu_clock(raw_smp_processor_id());
+	return local_clock();
 }

 /*
Index: linux-2.6/kernel/rcutorture.c
===================================================================
--- linux-2.6.orig/kernel/rcutorture.c
+++ linux-2.6/kernel/rcutorture.c
@@ -239,8 +239,7 @@ static unsigned long
 rcu_random(struct rcu_random_state *rrsp)
 {
 	if (--rrsp->rrs_count < 0) {
-		rrsp->rrs_state +=
-			(unsigned long)cpu_clock(raw_smp_processor_id());
+		rrsp->rrs_state += (unsigned long)local_clock();
 		rrsp->rrs_count = RCU_RANDOM_REFRESH;
 	}
 	rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -1670,7 +1670,7 @@ static void update_shares(struct sched_d
 	if (root_task_group_empty())
 		return;

-	now = cpu_clock(raw_smp_processor_id());
+	now = local_clock();
 	elapsed = now - sd->last_update;

 	if (elapsed >= (s64)(u64)sysctl_sched_shares_ratelimit) {
Index: linux-2.6/kernel/sched_clock.c
===================================================================
--- linux-2.6.orig/kernel/sched_clock.c
+++ linux-2.6/kernel/sched_clock.c
@@ -249,6 +249,18 @@ unsigned long long cpu_clock(int cpu)
 	return clock;
 }

+unsigned long long local_clock(void)
+{
+	unsigned long long clock;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	clock = sched_clock_cpu(smp_processor_id());
+	local_irq_restore(flags);
+
+	return clock;
+}
+
 #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */

 void sched_clock_init(void)
@@ -264,12 +276,17 @@ u64 sched_clock_cpu(int cpu)
 	return sched_clock();
 }

-
 unsigned long long cpu_clock(int cpu)
 {
 	return sched_clock_cpu(cpu);
 }

+unsigned long long local_clock(void)
+{
+	return sched_clock_cpu(0);
+}
+
 #endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */

 EXPORT_SYMBOL_GPL(cpu_clock);
+EXPORT_SYMBOL_GPL(local_clock);
Index: linux-2.6/kernel/trace/trace_clock.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_clock.c
+++ linux-2.6/kernel/trace/trace_clock.c
@@ -56,7 +56,7 @@ u64 notrace trace_clock_local(void)
  */
 u64 notrace trace_clock(void)
 {
-	return cpu_clock(raw_smp_processor_id());
+	return local_clock();
 }

Should I apply it first and then your today's patch or only the today's 
patch?

Regards,

Piotr Hosowicz


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