Re: [PATCH 2.6.28-rc4]lock_stat: Add "con-hungry" to show that how many person-time fight for the ticket spinlock

["Yang Xi" <yangxilkm@gmail.com>]

> I of course meant folding cpu and isspinlock into a combined bitfield
> (sorry for not being more clear), thereby saving space, this still takes
> 2*sizeof(int).
>
> We can safely take some bits from the cpu number as there currently are
> no plans for a 2g cpu machine, right SGI? :-)
Thanks, ok, 31bits enough for cpu at now stage. 1bit for isticketspinlock.
Here is the new one. Welcome more comments :).

Signed-off-by: Yang Xi  <hiyangxi@gmail.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4cf0ab1..20fee72 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -34,6 +34,7 @@ config X86
        select HAVE_ARCH_TRACEHOOK
        select HAVE_GENERIC_DMA_COHERENT if X86_32
        select HAVE_EFFICIENT_UNALIGNED_ACCESS
+       select HAVE_TICKET_SPINLOCK

 config ARCH_DEFCONFIG
        string
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index d17c919..da9cffc 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -172,6 +172,13 @@ static inline int
__ticket_spin_is_contended(raw_spinlock_t *lock)
        return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
 }

+static inline int __ticket_spin_nr_contended(raw_spinlock_t *lock)
+{
+       int tmp = ACCESS_ONCE(lock->slock);
+
+       return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) + 1;
+}
+
 #ifdef CONFIG_PARAVIRT
 /*
  * Define virtualization-friendly old-style lock byte lock, for use in
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 331e5f1..3b88f0c 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -136,6 +136,7 @@ enum bounce_type {
        bounce_acquired_read,
        bounce_contended_write,
        bounce_contended_read,
+       bounce_hungry,
        nr_bounce_types,

        bounce_acquired = bounce_acquired_write,
@@ -164,7 +165,8 @@ struct lockdep_map {
        struct lock_class               *class_cache;
        const char                      *name;
 #ifdef CONFIG_LOCK_STAT
-       int                             cpu;
+       unsigned int                    cpu:31;
+       unsigned int                    isticketspinlock:1;
 #endif
 };

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index e0c0fcc..e81c956 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -127,6 +127,12 @@ do {
                 \
 #define spin_is_contended(lock)
__raw_spin_is_contended(&(lock)->raw_lock)
 #endif

+#ifdef CONFIG_HAVE_TICKET_SPINLOCK
+#define spin_nr_contended(lock) __ticket_spin_nr_contended(&(lock)->raw_lock)
+#else
+#define spin_nr_contended(lock) (0)
+#endif
+
 /**
  * spin_unlock_wait - wait until the spinlock gets unlocked
  * @lock: the spinlock in question.
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 06e1571..28cd04e 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3000,6 +3000,13 @@ __lock_contended(struct lockdep_map *lock,
unsigned long ip)
        struct lock_class_stats *stats;
        unsigned int depth;
        int i, point;
+       spinlock_t *lock_ptr;
+       unsigned long hungry = 0;
+
+       if (lock->isticketspinlock) {
+               lock_ptr = container_of(lock, spinlock_t, dep_map);
+               hungry = spin_nr_contended(lock_ptr);
+       }

        depth = curr->lockdep_depth;
        if (DEBUG_LOCKS_WARN_ON(!depth))
@@ -3030,9 +3037,12 @@ found_it:
                stats->contention_point[point]++;
        if (lock->cpu != smp_processor_id())
                stats->bounces[bounce_contended + !!hlock->read]++;
+       stats->bounces[bounce_hungry] += hungry;
+
        put_lock_stats(stats);
 }

+
 static void
 __lock_acquired(struct lockdep_map *lock)
 {
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 20dbcbf..585601f 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -535,6 +535,7 @@ static void seq_stats(struct seq_file *m, struct
lock_stat_data *data)
                        seq_printf(m, "%40s:", name);

                seq_printf(m, "%14lu ", stats->bounces[bounce_contended_write]);
+               seq_printf(m, "%14lu ", stats->bounces[bounce_hungry]);
                seq_lock_time(m, &stats->write_waittime);
                seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_write]);
                seq_lock_time(m, &stats->write_holdtime);
@@ -584,11 +585,12 @@ static void seq_header(struct seq_file *m)
 {
        seq_printf(m, "lock_stat version 0.2\n");
        seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
-       seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s "
+       seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s %14s "
                        "%14s %14s\n",
                        "class name",
                        "con-bounces",
-                       "contentions",
+                       "con-hungry",
+                       "contentions",
                        "waittime-min",
                        "waittime-max",
                        "waittime-total",
@@ -597,7 +599,7 @@ static void seq_header(struct seq_file *m)
                        "holdtime-min",
                        "holdtime-max",
                        "holdtime-total");
-       seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
+       seq_line(m, '-', 0, 40 + 1 + 11 * (14 + 1));
        seq_printf(m, "\n");
 }

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b0f239e..b9eb62a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -318,6 +318,9 @@ config RT_MUTEX_TESTER
        help
          This option enables a rt-mutex tester.

+config HAVE_TICKET_SPINLOCK
+       bool
+
 config DEBUG_SPINLOCK
        bool "Spinlock and rw-lock debugging: basic checks"
        depends on DEBUG_KERNEL
diff --git a/lib/spinlock_debug.c b/lib/spinlock_debug.c
index 9c4b025..bba8d3e 100644
--- a/lib/spinlock_debug.c
+++ b/lib/spinlock_debug.c
@@ -27,6 +27,7 @@ void __spin_lock_init(spinlock_t *lock, const char *name,
        lock->magic = SPINLOCK_MAGIC;
        lock->owner = SPINLOCK_OWNER_INIT;
        lock->owner_cpu = -1;
+       lock->dep_map.isticketspinlock = 1;
 }

 EXPORT_SYMBOL(__spin_lock_init);