Messages in this thread | | | Date | Thu, 14 Apr 2016 14:47:18 -0400 | From | Waiman Long <> | Subject | Re: [PATCH] locking/pvqspinlock: Add lock holder CPU argument to pv_wait() |
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On 04/14/2016 10:34 AM, Pan Xinhui wrote: > hello, Waiman > I try your patch, thanks! > > also I do some improvement. > below code diff has been tested, it works for me. :) > > diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c > index ce2f75e..99f31e4 100644 > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -248,7 +248,8 @@ static __always_inline void set_locked(struct qspinlock *lock) > */ > > static __always_inline void __pv_init_node(struct mcs_spinlock *node) { } > -static __always_inline void __pv_wait_node(struct mcs_spinlock *node, > +static __always_inline void __pv_wait_node(struct qspinlock *lock, > + struct mcs_spinlock *node, > struct mcs_spinlock *prev) { } > static __always_inline void __pv_kick_node(struct qspinlock *lock, > struct mcs_spinlock *node) { } > @@ -407,7 +408,7 @@ queue: > prev = decode_tail(old); > WRITE_ONCE(prev->next, node); > > - pv_wait_node(node, prev); > + pv_wait_node(lock, node, prev); > arch_mcs_spin_lock_contended(&node->locked); > > /* > diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h > index 01a6d16..75ccfd3 100644 > --- a/kernel/locking/qspinlock_paravirt.h > +++ b/kernel/locking/qspinlock_paravirt.h > @@ -255,6 +257,19 @@ static struct pv_node *pv_unhash(struct qspinlock *lock) > BUG(); > } > > +static struct pv_node *pv_hash_lookup(struct qspinlock *lock) > +{ > + unsigned long offset, hash = hash_ptr(lock, pv_lock_hash_bits); > + struct pv_hash_entry *he; > + > + for_each_hash_entry(he, offset, hash) { > + if (READ_ONCE(he->lock) == lock) { > + return he->node; > + } > + } > + return NULL; > +} > + > /* > * Return true if when it is time to check the previous node which is not > * in a running state. > @@ -287,14 +303,17 @@ static void pv_init_node(struct mcs_spinlock *node) > * pv_kick_node() is used to set _Q_SLOW_VAL and fill in hash table on its > * behalf. > */ > -static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev) > +static void pv_wait_node(struct qspinlock *lock, struct mcs_spinlock *node, > + struct mcs_spinlock *prev) > { > struct pv_node *pn = (struct pv_node *)node; > struct pv_node *pp = (struct pv_node *)prev; > + struct pv_node *ph; > int waitcnt = 0; > int loop; > bool wait_early; > > + pn->prev_cpu = pp->cpu; > /* waitcnt processing will be compiled out if !QUEUED_LOCK_STAT */ > for (;; waitcnt++) { > for (wait_early = false, loop = SPIN_THRESHOLD; loop; loop--) { > @@ -322,7 +341,10 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev) > qstat_inc(qstat_pv_wait_node, true); > qstat_inc(qstat_pv_wait_again, waitcnt); > qstat_inc(qstat_pv_wait_early, wait_early); > - pv_wait(&pn->state, vcpu_halted); > + ph = pv_hash_lookup(lock); > + if (!ph) > + ph = pp; > + pv_wait(&pn->state, vcpu_halted, ph->prev_cpu); > } > > /* > > any comments are welcome. I put my patch here just for simplicity, or need I send it out in a new thread? > > thanks > xinhui > >
I have sent out a v2 patch that incorporate your change with some minor twists.
Cheers, Longman
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