search for: __pv_lock_wait

...+ * This should be fine however, kicking people for no reason is harmless. > + * > + * See the comment in pv_wait_node(). > + */ > + if (xchg(&pn->state, vcpu_running) == vcpu_halted) > + pv_kick(pn->cpu); > +} > + > +static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); > + > +/* > + * Wait for l->locked to become clear; halt the vcpu after a short spin. > + * __pv_queue_spin_unlock() will wake us. > + */ > +static void pv_wait_head(struct qspinlock *lock) > +{ > + struct __qspinlock *l = (void *)lock; > + int loop; > + > + fo...

...+ * This should be fine however, kicking people for no reason is harmless. > + * > + * See the comment in pv_wait_node(). > + */ > + if (xchg(&pn->state, vcpu_running) == vcpu_halted) > + pv_kick(pn->cpu); > +} > + > +static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); > + > +/* > + * Wait for l->locked to become clear; halt the vcpu after a short spin. > + * __pv_queue_spin_unlock() will wake us. > + */ > +static void pv_wait_head(struct qspinlock *lock) > +{ > + struct __qspinlock *l = (void *)lock; > + int loop; > + > + fo...

On Wed, Mar 18, 2015 at 04:50:37PM -0400, Waiman Long wrote: > >+ this_cpu_write(__pv_lock_wait, lock); > > We may run into the same problem of needing to have 4 queue nodes per CPU. > If an interrupt happens just after the write and before the actual wait and > it goes through the same sequence, it will overwrite the __pv_lock_wait[] > entry. So we may have lost wakeup. That...

On Wed, Mar 18, 2015 at 04:50:37PM -0400, Waiman Long wrote: > >+ this_cpu_write(__pv_lock_wait, lock); > > We may run into the same problem of needing to have 4 queue nodes per CPU. > If an interrupt happens just after the write and before the actual wait and > it goes through the same sequence, it will overwrite the __pv_lock_wait[] > entry. So we may have lost wakeup. That...

On Thu, Apr 02, 2015 at 12:28:30PM -0400, Waiman Long wrote: > On 04/01/2015 05:03 PM, Peter Zijlstra wrote: > >On Wed, Apr 01, 2015 at 03:58:58PM -0400, Waiman Long wrote: > >>On 04/01/2015 02:48 PM, Peter Zijlstra wrote: > >>I am sorry that I don't quite get what you mean here. My point is that in > >>the hashing step, a cpu will need to scan an empty

On Thu, Apr 02, 2015 at 12:28:30PM -0400, Waiman Long wrote: > On 04/01/2015 05:03 PM, Peter Zijlstra wrote: > >On Wed, Apr 01, 2015 at 03:58:58PM -0400, Waiman Long wrote: > >>On 04/01/2015 02:48 PM, Peter Zijlstra wrote: > >>I am sorry that I don't quite get what you mean here. My point is that in > >>the hashing step, a cpu will need to scan an empty

...this file" #endif +#include <linux/hash.h> + /* * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead * of spinning them. @@ -107,7 +109,84 @@ static void pv_kick_node(struct mcs_spin pv_kick(pn->cpu); } -static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); +/* + * Hash table using open addressing with an linear probe sequence. + * + * Since we should not be holding locks from NMI context (very rare indeed) the + * max load factor is 0.75, which is around the point where open adressing + * breaks down. + * + * Instead of probing just the immediate b...

...* entry could be re-used already. + * + * This should be fine however, kicking people for no reason is harmless. + * + * See the comment in pv_wait_node(). + */ + if (xchg(&pn->state, vcpu_running) == vcpu_halted) + pv_kick(pn->cpu); +} + +static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); + +/* + * Wait for l->locked to become clear; halt the vcpu after a short spin. + * __pv_queue_spin_unlock() will wake us. + */ +static void pv_wait_head(struct qspinlock *lock) +{ + struct __qspinlock *l = (void *)lock; + int loop; + + for (;;) { + for (loop = SPIN_THRESHOLD; loop; loop--) {...

...* entry could be re-used already. + * + * This should be fine however, kicking people for no reason is harmless. + * + * See the comment in pv_wait_node(). + */ + if (xchg(&pn->state, vcpu_running) == vcpu_halted) + pv_kick(pn->cpu); +} + +static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); + +/* + * Wait for l->locked to become clear; halt the vcpu after a short spin. + * __pv_queue_spin_unlock() will wake us. + */ +static void pv_wait_head(struct qspinlock *lock) +{ + struct __qspinlock *l = (void *)lock; + int loop; + + for (;;) { + for (loop = SPIN_THRESHOLD; loop; loop--) {...

...ude <linux/hash.h> +#include <linux/lfsr.h> + /* * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead * of spinning them. @@ -107,7 +110,120 @@ static void pv_kick_node(struct mcs_spin pv_kick(pn->cpu); } -static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); +/* + * Hash table using open addressing with an LFSR probe sequence. + * + * Since we should not be holding locks from NMI context (very rare indeed) the + * max load factor is 0.75, which is around the point where open addressing + * breaks down. + * + * Instead of probing just the immediate bu...

...ude <linux/hash.h> +#include <linux/lfsr.h> + /* * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead * of spinning them. @@ -107,7 +110,120 @@ static void pv_kick_node(struct mcs_spin pv_kick(pn->cpu); } -static DEFINE_PER_CPU(struct qspinlock *, __pv_lock_wait); +/* + * Hash table using open addressing with an LFSR probe sequence. + * + * Since we should not be holding locks from NMI context (very rare indeed) the + * max load factor is 0.75, which is around the point where open addressing + * breaks down. + * + * Instead of probing just the immediate bu...

Hi Waiman, As promised; here is the paravirt stuff I did during the trip to BOS last week. All the !paravirt patches are more or less the same as before (the only real change is the copyright lines in the first patch). The paravirt stuff is 'simple' and KVM only -- the Xen code was a little more convoluted and I've no real way to test that but it should be stright fwd to make work.

Hi Waiman, As promised; here is the paravirt stuff I did during the trip to BOS last week. All the !paravirt patches are more or less the same as before (the only real change is the copyright lines in the first patch). The paravirt stuff is 'simple' and KVM only -- the Xen code was a little more convoluted and I've no real way to test that but it should be stright fwd to make work.