On Tue, Sep 22, 2015 at 04:50:42PM -0400, Waiman Long wrote:
> @@ -100,10 +242,13 @@ static struct qspinlock **pv_hash(struct qspinlock
> *lock, struct pv_node *node)
> {
> unsigned long offset, hash = hash_ptr(lock, pv_lock_hash_bits);
> struct pv_hash_entry *he;
> + int hopcnt = 0;
>
> for_each_hash_entry(he, offset, hash) {
> + hopcnt++;
> if (!cmpxchg(&he->lock, NULL, lock)) {
> WRITE_ONCE(he->node, node);
> + pvstat_hop(hopcnt);
> return &he->lock;
> }
> }
> @@ -164,9 +309,10 @@ static void pv_init_node(struct mcs_spinlock *node)
> static void pv_wait_node(struct mcs_spinlock *node)
> {
> struct pv_node *pn = (struct pv_node *)node;
> + int waitcnt = 0;
> int loop;
>
> - for (;;) {
> + for (;; waitcnt++) {
> for (loop = SPIN_THRESHOLD; loop; loop--) {
> if (READ_ONCE(node->locked))
> return;
> @@ -250,6 +401,7 @@ static void pv_wait_head(struct qspinlock *lock, struct
> mcs_spinlock *node)
> struct pv_node *pn = (struct pv_node *)node;
> struct __qspinlock *l = (void *)lock;
> struct qspinlock **lp = NULL;
> + int waitcnt = 0;
> int loop;
>
> /*
> @@ -259,7 +411,7 @@ static void pv_wait_head(struct qspinlock *lock, struct
> mcs_spinlock *node)
> if (READ_ONCE(pn->state) == vcpu_hashed)
> lp = (struct qspinlock **)1;
>
> - for (;;) {
> + for (;; waitcnt++) {
> for (loop = SPIN_THRESHOLD; loop; loop--) {
> if (!READ_ONCE(l->locked))
> return;
These things are ugly; did you verify that they compile away for the
!stats case?
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