Messages in this thread | | | Date | Tue, 13 Oct 2015 22:05:20 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v7 3/5] locking/pvqspinlock: Collect slowpath lock statistics |
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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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