On Thu, Apr 02, 2015 at 09:48:34PM +0200, Peter Zijlstra wrote:
@@ -158,20 +257,20 @@ static void pv_wait_head(struct qspinloc
void __pv_queue_spin_unlock(struct qspinlock *lock)
{
struct __qspinlock *l = (void *)lock;
+ struct pv_hash_bucket *hb;
if (xchg(l-locked, 0)
On 04/02/2015 03:48 PM, Peter Zijlstra wrote:
On Thu, Apr 02, 2015 at 07:20:57PM +0200, Peter Zijlstra wrote:
pv_wait_head():
pv_hash()
/* MB as per cmpxchg */
cmpxchg(l-locked, _Q_LOCKED_VAL, _Q_SLOW_VAL);
VS
__pv_queue_spin_unlock():
if (xchg(l-locked, 0)
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
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 bucket to put the
On 03/19/2015 08:25 AM, Peter Zijlstra wrote:
On Thu, Mar 19, 2015 at 11:12:42AM +0100, Peter Zijlstra wrote:
So I was now thinking of hashing the lock pointer; let me go and quickly
put something together.
A little something like so; ideally we'd allocate the hashtable since
NR_CPUS is kinda
On Wed, Apr 01, 2015 at 12:20:30PM -0400, Waiman Long wrote:
After more careful reading, I think the assumption that the presence of an
unused bucket means there is no match is not true. Consider the scenario:
1. cpu 0 puts lock1 into hb[0]
2. cpu 1 puts lock2 into hb[1]
3. cpu 2 clears
On Wed, Apr 01, 2015 at 07:12:23PM +0200, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 12:20:30PM -0400, Waiman Long wrote:
After more careful reading, I think the assumption that the presence of an
unused bucket means there is no match is not true. Consider the scenario:
1. cpu 0 puts
On Wed, Apr 01, 2015 at 07:42:39PM +0200, Peter Zijlstra wrote:
Hohumm.. time to think more I think ;-)
So bear with me, I've not really pondered this well so it could be full
of holes (again).
After the cmpxchg(l-locked, _Q_LOCKED_VAL, _Q_SLOW_VAL) succeeds the
spin_unlock() must do the
On 04/01/2015 02:17 PM, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 07:42:39PM +0200, Peter Zijlstra wrote:
Hohumm.. time to think more I think ;-)
So bear with me, I've not really pondered this well so it could be full
of holes (again).
After the cmpxchg(l-locked, _Q_LOCKED_VAL,
On Wed, Apr 01, 2015 at 02:54:45PM -0400, Waiman Long wrote:
On 04/01/2015 02:17 PM, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 07:42:39PM +0200, Peter Zijlstra wrote:
Hohumm.. time to think more I think ;-)
So bear with me, I've not really pondered this well so it could be full
of holes
On 04/01/2015 02:48 PM, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 02:54:45PM -0400, Waiman Long wrote:
On 04/01/2015 02:17 PM, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 07:42:39PM +0200, Peter Zijlstra wrote:
Hohumm.. time to think more I think ;-)
So bear with me, I've not really
On 04/01/2015 01:12 PM, Peter Zijlstra wrote:
On Wed, Apr 01, 2015 at 12:20:30PM -0400, Waiman Long wrote:
After more careful reading, I think the assumption that the presence of an
unused bucket means there is no match is not true. Consider the scenario:
1. cpu 0 puts lock1 into hb[0]
2. cpu
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 bucket to put the lock
in. In the interim, an previously used
On 03/19/2015 08:25 AM, Peter Zijlstra wrote:
On Thu, Mar 19, 2015 at 11:12:42AM +0100, Peter Zijlstra wrote:
So I was now thinking of hashing the lock pointer; let me go and quickly
put something together.
A little something like so; ideally we'd allocate the hashtable since
NR_CPUS is kinda
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
On Thu, Mar 19, 2015 at 01:25:36PM +0100, Peter Zijlstra wrote:
+static struct qspinlock **pv_hash(struct qspinlock *lock)
+{
+ u32 hash = hash_ptr(lock, PV_LOCK_HASH_BITS);
+ struct pv_hash_bucket *hb, *end;
+
+ if (!hash)
+ hash = 1;
+
+ hb =
On 03/16/2015 09:16 AM, Peter Zijlstra wrote:
Implement simple paravirt support for the qspinlock.
Provide a separate (second) version of the spin_lock_slowpath for
paravirt along with a special unlock path.
The second slowpath is generated by adding a few pv hooks to the
normal slowpath, but
Implement simple paravirt support for the qspinlock.
Provide a separate (second) version of the spin_lock_slowpath for
paravirt along with a special unlock path.
The second slowpath is generated by adding a few pv hooks to the
normal slowpath, but where those will compile away for the native
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