[Xen-devel] [PATCH 4 of 4] xen: measure how long spinlocks spend blocking

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/xen/spinlock.c |   60 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -29,12 +29,14 @@
        u32 released_slow;
        u32 released_slow_kicked;
 
-#define HISTO_BUCKETS  20
-       u32 histo_spin_fast[HISTO_BUCKETS+1];
-       u32 histo_spin[HISTO_BUCKETS+1];
+#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 spinning_time;
-       u64 total_time;
+       u64 time_total;
+       u64 time_spinning;
+       u64 time_blocked;
 } spinlock_stats;
 
 static u8 zero_stats;
@@ -70,20 +72,28 @@
                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_fast);
-       spinlock_stats.spinning_time += delta;
+       __spin_time_accum(delta, spinlock_stats.histo_spin_spinning);
+       spinlock_stats.time_spinning += delta;
 }
 
-static inline void spin_time_accum(u64 start)
+static inline void spin_time_accum_total(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_total);
+       spinlock_stats.time_total += delta;
+}
+
+static inline void spin_time_accum_blocked(u64 start)
+{
+       u32 delta = xen_clocksource_read() - start;
+
+       __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 @@
        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(u64 start)
+static inline void spin_time_accum_spinning(u64 start)
+{
+}
+static inline void spin_time_accum_blocked(u64 start)
 {
 }
 #endif  /* CONFIG_XEN_DEBUG_FS */
@@ -175,10 +188,13 @@
        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 @@
 out:
        raw_local_irq_restore(flags);
        unspinning_lock(xl, prev);
+       spin_time_accum_blocked(start);
+
        return ret;
 }
 
@@ -262,12 +280,12 @@
                    : "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 @@
                           &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;
 }



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