xen: measure how long spinlocks spend blocking

Measure how long spinlocks spend blocked.  Also rename some fields to
be more consistent.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/xen/spinlock.c

@@ -29,12 +29,14 @@ static struct xen_spinlock_stats
 	u32 released_slow;
 	u32 released_slow_kicked;
 
-#define HISTO_BUCKETS	20
-	u32 histo_spin_fast[HISTO_BUCKETS+1];
-	u32 histo_spin[HISTO_BUCKETS+1];
-
-	u64 spinning_time;
-	u64 total_time;
+#define HISTO_BUCKETS	30
+	u32 histo_spin_total[HISTO_BUCKETS+1];
+	u32 histo_spin_spinning[HISTO_BUCKETS+1];
+	u32 histo_spin_blocked[HISTO_BUCKETS+1];
+
+	u64 time_total;
+	u64 time_spinning;
+	u64 time_blocked;
 } spinlock_stats;
 
 static u8 zero_stats;
@@ -70,20 +72,28 @@ static void __spin_time_accum(u64 delta, u32 *array)
 		array[HISTO_BUCKETS]++;
 }
 
-static inline void spin_time_accum_fast(u64 start)
+static inline void spin_time_accum_spinning(u64 start)
+{
+	u32 delta = xen_clocksource_read() - start;
+
+	__spin_time_accum(delta, spinlock_stats.histo_spin_spinning);
+	spinlock_stats.time_spinning += delta;
+}
+
+static inline void spin_time_accum_total(u64 start)
 {
 	u32 delta = xen_clocksource_read() - start;
 
-	__spin_time_accum(delta, spinlock_stats.histo_spin_fast);
-	spinlock_stats.spinning_time += delta;
+	__spin_time_accum(delta, spinlock_stats.histo_spin_total);
+	spinlock_stats.time_total += delta;
 }
 
-static inline void spin_time_accum(u64 start)
+static inline void spin_time_accum_blocked(u64 start)
 {
 	u32 delta = xen_clocksource_read() - start;
 
-	__spin_time_accum(delta, spinlock_stats.histo_spin);
-	spinlock_stats.total_time += delta;
+	__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
+	spinlock_stats.time_blocked += delta;
 }
 #else  /* !CONFIG_XEN_DEBUG_FS */
 #define TIMEOUT			(1 << 10)
@@ -94,10 +104,13 @@ static inline u64 spin_time_start(void)
 	return 0;
 }
 
-static inline void spin_time_accum_fast(u64 start)
+static inline void spin_time_accum_total(u64 start)
+{
+}
+static inline void spin_time_accum_spinning(u64 start)
 {
 }
-static inline void spin_time_accum(u64 start)
+static inline void spin_time_accum_blocked(u64 start)
 {
 }
 #endif  /* CONFIG_XEN_DEBUG_FS */
@@ -175,11 +188,14 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
 	int irq = __get_cpu_var(lock_kicker_irq);
 	int ret;
 	unsigned long flags;
+	u64 start;
 
 	/* If kicker interrupts not initialized yet, just spin */
 	if (irq == -1)
 		return 0;
 
+	start = spin_time_start();
+
 	/* announce we're spinning */
 	prev = spinning_lock(xl);
 
@@ -230,6 +246,8 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
 out:
 	raw_local_irq_restore(flags);
 	unspinning_lock(xl, prev);
+	spin_time_accum_blocked(start);
+
 	return ret;
 }
 
@@ -262,12 +280,12 @@ static inline void __xen_spin_lock(struct raw_spinlock *lock, bool irq_enable)
 		    : "1" (1)
 		    : "memory");
 
-		spin_time_accum_fast(start_spin_fast);
+		spin_time_accum_spinning(start_spin_fast);
 
 	} while (unlikely(oldval != 0 &&
 			  (TIMEOUT == ~0 || !xen_spin_lock_slow(lock, irq_enable))));
 
-	spin_time_accum(start_spin);
+	spin_time_accum_total(start_spin);
 }
 
 static void xen_spin_lock(struct raw_spinlock *lock)
@@ -385,14 +403,18 @@ static int __init xen_spinlock_debugfs(void)
 			   &spinlock_stats.released_slow_kicked);
 
 	debugfs_create_u64("time_spinning", 0444, d_spin_debug,
-			   &spinlock_stats.spinning_time);
+			   &spinlock_stats.time_spinning);
+	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
+			   &spinlock_stats.time_blocked);
 	debugfs_create_u64("time_total", 0444, d_spin_debug,
-			   &spinlock_stats.total_time);
+			   &spinlock_stats.time_total);
 
 	xen_debugfs_create_u32_array("histo_total", 0444, d_spin_debug,
-				     spinlock_stats.histo_spin, HISTO_BUCKETS + 1);
+				     spinlock_stats.histo_spin_total, HISTO_BUCKETS + 1);
 	xen_debugfs_create_u32_array("histo_spinning", 0444, d_spin_debug,
-				     spinlock_stats.histo_spin_fast, HISTO_BUCKETS + 1);
+				     spinlock_stats.histo_spin_spinning, HISTO_BUCKETS + 1);
+	xen_debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
+				     spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
 
 	return 0;
 }