perfcounters: restructure x86 counter math

Impact: restructure code

Change counter math from absolute values to clear delta logic.

We try to extract elapsed deltas from the raw hw counter - and put
that into the generic counter.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -643,7 +643,7 @@ config X86_UP_IOAPIC
 config X86_LOCAL_APIC
 	def_bool y
 	depends on X86_64 || (X86_32 && (X86_UP_APIC || (SMP && !X86_VOYAGER) || X86_GENERICARCH))
-	select HAVE_PERF_COUNTERS
+	select HAVE_PERF_COUNTERS if (!M386 && !M486)
 
 config X86_IO_APIC
 	def_bool y

include/linux/perf_counter.h

@@ -91,14 +91,16 @@ struct perf_counter_hw_event {
  * struct hw_perf_counter - performance counter hardware details:
  */
 struct hw_perf_counter {
+#ifdef CONFIG_PERF_COUNTERS
 	u64				config;
 	unsigned long			config_base;
 	unsigned long			counter_base;
 	int				nmi;
 	unsigned int			idx;
-	u64				prev_count;
+	atomic64_t			prev_count;
 	u64				irq_period;
-	s32				next_count;
+	atomic64_t			period_left;
+#endif
 };
 
 /*
@@ -140,17 +142,15 @@ enum perf_counter_active_state {
  * struct perf_counter - performance counter kernel representation:
  */
 struct perf_counter {
+#ifdef CONFIG_PERF_COUNTERS
 	struct list_head		list_entry;
 	struct list_head		sibling_list;
 	struct perf_counter		*group_leader;
 	const struct hw_perf_counter_ops *hw_ops;
 
 	enum perf_counter_active_state	state;
-#if BITS_PER_LONG == 64
 	atomic64_t			count;
-#else
-	atomic_t			count32[2];
-#endif
+
 	struct perf_counter_hw_event	hw_event;
 	struct hw_perf_counter		hw;
 
@@ -172,6 +172,7 @@ struct perf_counter {
 	struct perf_data		*irqdata;
 	struct perf_data		*usrdata;
 	struct perf_data		data[2];
+#endif
 };
 
 /**
@@ -220,8 +221,6 @@ extern void perf_counter_notify(struct pt_regs *regs);
 extern void perf_counter_print_debug(void);
 extern u64 hw_perf_save_disable(void);
 extern void hw_perf_restore(u64 ctrl);
-extern void atomic64_counter_set(struct perf_counter *counter, u64 val64);
-extern u64 atomic64_counter_read(struct perf_counter *counter);
 extern int perf_counter_task_disable(void);
 extern int perf_counter_task_enable(void);
 

kernel/perf_counter.c

@@ -47,64 +47,6 @@ u64 __weak hw_perf_save_disable(void)		{ return 0; }
 void __weak hw_perf_restore(u64 ctrl)		{ }
 void __weak hw_perf_counter_setup(void)		{ }
 
-#if BITS_PER_LONG == 64
-
-/*
- * Read the cached counter in counter safe against cross CPU / NMI
- * modifications. 64 bit version - no complications.
- */
-static inline u64 perf_counter_read_safe(struct perf_counter *counter)
-{
-	return (u64) atomic64_read(&counter->count);
-}
-
-void atomic64_counter_set(struct perf_counter *counter, u64 val)
-{
-	atomic64_set(&counter->count, val);
-}
-
-u64 atomic64_counter_read(struct perf_counter *counter)
-{
-	return atomic64_read(&counter->count);
-}
-
-#else
-
-/*
- * Read the cached counter in counter safe against cross CPU / NMI
- * modifications. 32 bit version.
- */
-static u64 perf_counter_read_safe(struct perf_counter *counter)
-{
-	u32 cntl, cnth;
-
-	local_irq_disable();
-	do {
-		cnth = atomic_read(&counter->count32[1]);
-		cntl = atomic_read(&counter->count32[0]);
-	} while (cnth != atomic_read(&counter->count32[1]));
-
-	local_irq_enable();
-
-	return cntl | ((u64) cnth) << 32;
-}
-
-void atomic64_counter_set(struct perf_counter *counter, u64 val64)
-{
-	u32 *val32 = (void *)&val64;
-
-	atomic_set(counter->count32 + 0, *(val32 + 0));
-	atomic_set(counter->count32 + 1, *(val32 + 1));
-}
-
-u64 atomic64_counter_read(struct perf_counter *counter)
-{
-	return atomic_read(counter->count32 + 0) |
-		(u64) atomic_read(counter->count32 + 1) << 32;
-}
-
-#endif
-
 static void
 list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
 {
@@ -280,11 +222,11 @@ static void __perf_install_in_context(void *info)
 	ctx->nr_counters++;
 
 	if (cpuctx->active_oncpu < perf_max_counters) {
-		counter->hw_ops->hw_perf_counter_enable(counter);
 		counter->state = PERF_COUNTER_STATE_ACTIVE;
 		counter->oncpu = cpu;
 		ctx->nr_active++;
 		cpuctx->active_oncpu++;
+		counter->hw_ops->hw_perf_counter_enable(counter);
 	}
 
 	if (!ctx->task && cpuctx->max_pertask)
@@ -624,7 +566,7 @@ static u64 perf_counter_read(struct perf_counter *counter)
 					 __hw_perf_counter_read, counter, 1);
 	}
 
-	return perf_counter_read_safe(counter);
+	return atomic64_read(&counter->count);
 }
 
 /*
@@ -921,7 +863,7 @@ static void cpu_clock_perf_counter_read(struct perf_counter *counter)
 {
 	int cpu = raw_smp_processor_id();
 
-	atomic64_counter_set(counter, cpu_clock(cpu));
+	atomic64_set(&counter->count, cpu_clock(cpu));
 }
 
 static const struct hw_perf_counter_ops perf_ops_cpu_clock = {
@@ -940,7 +882,7 @@ static void task_clock_perf_counter_disable(struct perf_counter *counter)
 
 static void task_clock_perf_counter_read(struct perf_counter *counter)
 {
-	atomic64_counter_set(counter, current->se.sum_exec_runtime);
+	atomic64_set(&counter->count, current->se.sum_exec_runtime);
 }
 
 static const struct hw_perf_counter_ops perf_ops_task_clock = {