[RFC][PATCH 02/11] perf_counter: generic context switch event

[Peter Zijlstra]

use the generic software events for context switches.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 include/linux/sched.h |    1 
 kernel/perf_counter.c |   60 +++-----------------------------------------------
 kernel/sched.c        |    6 -----
 3 files changed, 4 insertions(+), 63 deletions(-)

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -137,7 +137,6 @@ extern unsigned long nr_running(void);
 extern unsigned long nr_uninterruptible(void);
 extern unsigned long nr_active(void);
 extern unsigned long nr_iowait(void);
-extern u64 cpu_nr_switches(int cpu);
 extern u64 cpu_nr_migrations(int cpu);
 
 extern unsigned long get_parent_ip(unsigned long addr);
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -710,10 +710,13 @@ void perf_counter_task_sched_out(struct 
 {
 	struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
 	struct perf_counter_context *ctx = &task->perf_counter_ctx;
+	struct pt_regs *regs;
 
 	if (likely(!cpuctx->task_ctx))
 		return;
 
+	regs = task_pt_regs(task);
+	perf_swcounter_event(PERF_COUNT_CONTEXT_SWITCHES, 1, 1, regs);
 	__perf_counter_sched_out(ctx, cpuctx);
 
 	cpuctx->task_ctx = NULL;
@@ -1671,58 +1674,6 @@ static const struct hw_perf_counter_ops 
 };
 
 /*
- * Software counter: context switches
- */
-
-static u64 get_context_switches(struct perf_counter *counter)
-{
-	struct task_struct *curr = counter->ctx->task;
-
-	if (curr)
-		return curr->nvcsw + curr->nivcsw;
-	return cpu_nr_switches(smp_processor_id());
-}
-
-static void context_switches_perf_counter_update(struct perf_counter *counter)
-{
-	u64 prev, now;
-	s64 delta;
-
-	prev = atomic64_read(&counter->hw.prev_count);
-	now = get_context_switches(counter);
-
-	atomic64_set(&counter->hw.prev_count, now);
-
-	delta = now - prev;
-
-	atomic64_add(delta, &counter->count);
-}
-
-static void context_switches_perf_counter_read(struct perf_counter *counter)
-{
-	context_switches_perf_counter_update(counter);
-}
-
-static int context_switches_perf_counter_enable(struct perf_counter *counter)
-{
-	if (counter->prev_state <= PERF_COUNTER_STATE_OFF)
-		atomic64_set(&counter->hw.prev_count,
-			     get_context_switches(counter));
-	return 0;
-}
-
-static void context_switches_perf_counter_disable(struct perf_counter *counter)
-{
-	context_switches_perf_counter_update(counter);
-}
-
-static const struct hw_perf_counter_ops perf_ops_context_switches = {
-	.enable		= context_switches_perf_counter_enable,
-	.disable	= context_switches_perf_counter_disable,
-	.read		= context_switches_perf_counter_read,
-};
-
-/*
  * Software counter: cpu migrations
  */
 
@@ -1811,11 +1762,8 @@ sw_perf_counter_init(struct perf_counter
 	case PERF_COUNT_PAGE_FAULTS:
 	case PERF_COUNT_PAGE_FAULTS_MIN:
 	case PERF_COUNT_PAGE_FAULTS_MAJ:
-		hw_ops = &perf_ops_generic;
-		break;
 	case PERF_COUNT_CONTEXT_SWITCHES:
-		if (!counter->hw_event.exclude_kernel)
-			hw_ops = &perf_ops_context_switches;
+		hw_ops = &perf_ops_generic;
 		break;
 	case PERF_COUNT_CPU_MIGRATIONS:
 		if (!counter->hw_event.exclude_kernel)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2911,14 +2911,8 @@ unsigned long nr_active(void)
 
 /*
  * Externally visible per-cpu scheduler statistics:
- * cpu_nr_switches(cpu) - number of context switches on that cpu
  * cpu_nr_migrations(cpu) - number of migrations into that cpu
  */
-u64 cpu_nr_switches(int cpu)
-{
-	return cpu_rq(cpu)->nr_switches;
-}
-
 u64 cpu_nr_migrations(int cpu)
 {
 	return cpu_rq(cpu)->nr_migrations_in;

-- 

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