1 files changed, 162 insertions, 3 deletions

diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 4884bc603aa7..0d8f3b2d9bec 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -4,6 +4,8 @@
  */
 #include <linux/kernel_stat.h>
 #include <linux/spinlock.h>
+#include <linux/debugfs.h>
+#include <linux/log2.h>
 
 #include <asm/paravirt.h>
 
@@ -11,6 +13,93 @@
 #include <xen/events.h>
 
 #include "xen-ops.h"
+#include "debugfs.h"
+
+#ifdef CONFIG_XEN_DEBUG_FS
+static struct xen_spinlock_stats
+{
+        u64 taken;
+        u32 taken_slow;
+        u32 taken_slow_nested;
+        u32 taken_slow_pickup;
+        u32 taken_slow_spurious;
+
+        u64 released;
+        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;
+} spinlock_stats;
+
+static u8 zero_stats;
+
+static unsigned lock_timeout = 1 << 10;
+#define TIMEOUT lock_timeout
+
+static inline void check_zero(void)
+{
+        if (unlikely(zero_stats)) {
+                memset(&spinlock_stats, 0, sizeof(spinlock_stats));
+                zero_stats = 0;
+        }
+}
+
+#define ADD_STATS(elem, val)                    \
+        do { check_zero(); spinlock_stats.elem += (val); } while(0)
+
+static inline u64 spin_time_start(void)
+{
+        return xen_clocksource_read();
+}
+
+static void __spin_time_accum(u64 delta, u32 *array)
+{
+        unsigned index = ilog2(delta);
+
+        check_zero();
+
+        if (index < HISTO_BUCKETS)
+                array[index]++;
+        else
+                array[HISTO_BUCKETS]++;
+}
+
+static inline void spin_time_accum_fast(u64 start)
+{
+        u32 delta = xen_clocksource_read() - start;
+
+        __spin_time_accum(delta, spinlock_stats.histo_spin_fast);
+        spinlock_stats.spinning_time += delta;
+}
+
+static inline void spin_time_accum(u64 start)
+{
+        u32 delta = xen_clocksource_read() - start;
+
+        __spin_time_accum(delta, spinlock_stats.histo_spin);
+        spinlock_stats.total_time += delta;
+}
+#else  /* !CONFIG_XEN_DEBUG_FS */
+#define TIMEOUT                 (1 << 10)
+#define ADD_STATS(elem, val)    do { (void)(val); } while(0)
+
+static inline u64 spin_time_start(void)
+{
+        return 0;
+}
+
+static inline void spin_time_accum_fast(u64 start)
+{
+}
+static inline void spin_time_accum(u64 start)
+{
+}
+#endif  /* CONFIG_XEN_DEBUG_FS */
 
 struct xen_spinlock {
         unsigned char lock;             /* 0 -> free; 1 -> locked */
@@ -92,6 +181,9 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
         /* announce we're spinning */
         prev = spinning_lock(xl);
 
+        ADD_STATS(taken_slow, 1);
+        ADD_STATS(taken_slow_nested, prev != NULL);
+
         do {
                 /* clear pending */
                 xen_clear_irq_pending(irq);
@@ -100,6 +192,8 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
                    we weren't looking  */
                 ret = xen_spin_trylock(lock);
                 if (ret) {
+                        ADD_STATS(taken_slow_pickup, 1);
+
                         /*
                          * If we interrupted another spinlock while it
                          * was blocking, make sure it doesn't block
@@ -120,6 +214,7 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
                  * pending.
                  */
                 xen_poll_irq(irq);
+                ADD_STATS(taken_slow_spurious, !xen_test_irq_pending(irq));
         } while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */
 
         kstat_this_cpu.irqs[irq]++;
@@ -132,11 +227,18 @@ out:
 static void xen_spin_lock(struct raw_spinlock *lock)
 {
         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
-        int timeout;
+        unsigned timeout;
         u8 oldval;
+        u64 start_spin;
+
+        ADD_STATS(taken, 1);
+
+        start_spin = spin_time_start();
 
         do {
-                timeout = 1 << 10;
+                u64 start_spin_fast = spin_time_start();
+
+                timeout = TIMEOUT;
 
                 asm("1: xchgb %1,%0\n"
                     "   testb %1,%1\n"
@@ -151,16 +253,22 @@ static void xen_spin_lock(struct raw_spinlock *lock)
                     : "1" (1)
                     : "memory");
 
-        } while (unlikely(oldval != 0 && !xen_spin_lock_slow(lock)));
+                spin_time_accum_fast(start_spin_fast);
+        } while (unlikely(oldval != 0 && (TIMEOUT == ~0 || !xen_spin_lock_slow(lock))));
+
+        spin_time_accum(start_spin);
 }
 
 static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
 {
         int cpu;
 
+        ADD_STATS(released_slow, 1);
+
         for_each_online_cpu(cpu) {
                 /* XXX should mix up next cpu selection */
                 if (per_cpu(lock_spinners, cpu) == xl) {
+                        ADD_STATS(released_slow_kicked, 1);
                         xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
                         break;
                 }
@@ -171,6 +279,8 @@ static void xen_spin_unlock(struct raw_spinlock *lock)
 {
         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 
+        ADD_STATS(released, 1);
+
         smp_wmb();              /* make sure no writes get moved after unlock */
         xl->lock = 0;           /* release lock */
 
@@ -216,3 +326,52 @@ void __init xen_init_spinlocks(void)
         pv_lock_ops.spin_trylock = xen_spin_trylock;
         pv_lock_ops.spin_unlock = xen_spin_unlock;
 }
+
+#ifdef CONFIG_XEN_DEBUG_FS
+
+static struct dentry *d_spin_debug;
+
+static int __init xen_spinlock_debugfs(void)
+{
+        struct dentry *d_xen = xen_init_debugfs();
+
+        if (d_xen == NULL)
+                return -ENOMEM;
+
+        d_spin_debug = debugfs_create_dir("spinlocks", d_xen);
+
+        debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
+
+        debugfs_create_u32("timeout", 0644, d_spin_debug, &lock_timeout);
+
+        debugfs_create_u64("taken", 0444, d_spin_debug, &spinlock_stats.taken);
+        debugfs_create_u32("taken_slow", 0444, d_spin_debug,
+                           &spinlock_stats.taken_slow);
+        debugfs_create_u32("taken_slow_nested", 0444, d_spin_debug,
+                           &spinlock_stats.taken_slow_nested);
+        debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
+                           &spinlock_stats.taken_slow_pickup);
+        debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug,
+                           &spinlock_stats.taken_slow_spurious);
+
+        debugfs_create_u64("released", 0444, d_spin_debug, &spinlock_stats.released);
+        debugfs_create_u32("released_slow", 0444, d_spin_debug,
+                           &spinlock_stats.released_slow);
+        debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
+                           &spinlock_stats.released_slow_kicked);
+
+        debugfs_create_u64("time_spinning", 0444, d_spin_debug,
+                           &spinlock_stats.spinning_time);
+        debugfs_create_u64("time_total", 0444, d_spin_debug,
+                           &spinlock_stats.total_time);
+
+        xen_debugfs_create_u32_array("histo_total", 0444, d_spin_debug,
+                                     spinlock_stats.histo_spin, HISTO_BUCKETS + 1);
+        xen_debugfs_create_u32_array("histo_spinning", 0444, d_spin_debug,
+                                     spinlock_stats.histo_spin_fast, HISTO_BUCKETS + 1);
+
+        return 0;
+}
+fs_initcall(xen_spinlock_debugfs);
+
+#endif  /* CONFIG_XEN_DEBUG_FS */