Displaying 20 results from an estimated 45 matches for "_q_slow_val".
2015 Apr 02
3
[PATCH 8/9] qspinlock: Generic paravirt support
...bound in cost to the same number if probes we required for
> >insertion and avoids the full array scan.
> >
> >Now I think we can indeed do this, if as said earlier we do not clear
> >the bucket on insert if the cmpxchg succeeds, in that case the unlock
> >will observe _Q_SLOW_VAL and do the lookup, the lookup will then find
> >the entry. And we then need the unlock to clear the entry.
> >_Q_SLOW_VAL
> >Does that explain this? Or should I try again with code?
>
> OK, I got your proposal now. However, there is still the issue that setting
> the _Q_...
2015 Apr 02
3
[PATCH 8/9] qspinlock: Generic paravirt support
...bound in cost to the same number if probes we required for
> >insertion and avoids the full array scan.
> >
> >Now I think we can indeed do this, if as said earlier we do not clear
> >the bucket on insert if the cmpxchg succeeds, in that case the unlock
> >will observe _Q_SLOW_VAL and do the lookup, the lookup will then find
> >the entry. And we then need the unlock to clear the entry.
> >_Q_SLOW_VAL
> >Does that explain this? Or should I try again with code?
>
> OK, I got your proposal now. However, there is still the issue that setting
> the _Q_...
2015 Apr 13
1
[PATCH v15 09/15] pvqspinlock: Implement simple paravirt support for the qspinlock
...cked))
> >>+ return;
> >>+
> >>+ cpu_relax();
> >>+ }
> >>+
> >>+ WRITE_ONCE(pn->state, vcpu_halted);
> >>+ if (!lp)
> >>+ lp = pv_hash(lock, pn);
> >>+ /*
> >>+ * lp must be set before setting _Q_SLOW_VAL
> >>+ *
> >>+ * [S] lp = lock [RmW] l = l->locked = 0
> >>+ * MB MB
> >>+ * [S] l->locked = _Q_SLOW_VAL [L] lp
> >>+ *
> >>+ * Matches the cmpxchg() in pv_queue_spin_unlock().
&...
2015 Apr 13
1
[PATCH v15 09/15] pvqspinlock: Implement simple paravirt support for the qspinlock
...cked))
> >>+ return;
> >>+
> >>+ cpu_relax();
> >>+ }
> >>+
> >>+ WRITE_ONCE(pn->state, vcpu_halted);
> >>+ if (!lp)
> >>+ lp = pv_hash(lock, pn);
> >>+ /*
> >>+ * lp must be set before setting _Q_SLOW_VAL
> >>+ *
> >>+ * [S] lp = lock [RmW] l = l->locked = 0
> >>+ * MB MB
> >>+ * [S] l->locked = _Q_SLOW_VAL [L] lp
> >>+ *
> >>+ * Matches the cmpxchg() in pv_queue_spin_unlock().
&...
2015 Apr 02
0
[PATCH 8/9] qspinlock: Generic paravirt support
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) != _Q_SLOW_VAL)
> return;
>
> /* MB as per xchg */
> pv_hash_find(lock);
>
>
Something like so.. compile tested only.
I took out the LFSR because that was likely over engineer...
2015 Apr 01
2
[PATCH 8/9] qspinlock: Generic paravirt support
...probe until we find the entry.
This will be bound in cost to the same number if probes we required for
insertion and avoids the full array scan.
Now I think we can indeed do this, if as said earlier we do not clear
the bucket on insert if the cmpxchg succeeds, in that case the unlock
will observe _Q_SLOW_VAL and do the lookup, the lookup will then find
the entry. And we then need the unlock to clear the entry.
Does that explain this? Or should I try again with code?
2015 Apr 01
2
[PATCH 8/9] qspinlock: Generic paravirt support
...probe until we find the entry.
This will be bound in cost to the same number if probes we required for
insertion and avoids the full array scan.
Now I think we can indeed do this, if as said earlier we do not clear
the bucket on insert if the cmpxchg succeeds, in that case the unlock
will observe _Q_SLOW_VAL and do the lookup, the lookup will then find
the entry. And we then need the unlock to clear the entry.
Does that explain this? Or should I try again with code?
2015 Apr 09
6
[PATCH v15 09/15] pvqspinlock: Implement simple paravirt support for the qspinlock
...== val
> + * pv_kick(cpu) -- wakes a suspended vcpu
> + *
> + * Using these we implement __pv_queue_spin_lock_slowpath() and
> + * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
> + * native_queue_spin_unlock().
> + */
> +
> +#define _Q_SLOW_VAL (3U << _Q_LOCKED_OFFSET)
> +
> +enum vcpu_state {
> + vcpu_running = 0,
> + vcpu_halted,
> +};
> +
> +struct pv_node {
> + struct mcs_spinlock mcs;
> + struct mcs_spinlock __res[3];
> +
> + int cpu;
> + u8 state;
> +};
> +
> +/*
> + * Hash t...
2015 Apr 09
6
[PATCH v15 09/15] pvqspinlock: Implement simple paravirt support for the qspinlock
...== val
> + * pv_kick(cpu) -- wakes a suspended vcpu
> + *
> + * Using these we implement __pv_queue_spin_lock_slowpath() and
> + * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
> + * native_queue_spin_unlock().
> + */
> +
> +#define _Q_SLOW_VAL (3U << _Q_LOCKED_OFFSET)
> +
> +enum vcpu_state {
> + vcpu_running = 0,
> + vcpu_halted,
> +};
> +
> +struct pv_node {
> + struct mcs_spinlock mcs;
> + struct mcs_spinlock __res[3];
> +
> + int cpu;
> + u8 state;
> +};
> +
> +/*
> + * Hash t...
2015 Apr 09
2
[PATCH v15 13/15] pvqspinlock: Only kick CPU at unlock time
On Mon, Apr 06, 2015 at 10:55:48PM -0400, Waiman Long wrote:
> @@ -219,24 +236,30 @@ static void pv_wait_node(struct mcs_spinlock *node)
> }
>
> /*
> + * Called after setting next->locked = 1 & lock acquired.
> + * Check if the the CPU has been halted. If so, set the _Q_SLOW_VAL flag
> + * and put an entry into the lock hash table to be waken up at unlock time.
> */
> -static void pv_kick_node(struct mcs_spinlock *node)
> +static void pv_scan_next(struct qspinlock *lock, struct mcs_spinlock *node)
I'm not too sure about that name change..
> {
>...
2015 Apr 09
2
[PATCH v15 13/15] pvqspinlock: Only kick CPU at unlock time
On Mon, Apr 06, 2015 at 10:55:48PM -0400, Waiman Long wrote:
> @@ -219,24 +236,30 @@ static void pv_wait_node(struct mcs_spinlock *node)
> }
>
> /*
> + * Called after setting next->locked = 1 & lock acquired.
> + * Check if the the CPU has been halted. If so, set the _Q_SLOW_VAL flag
> + * and put an entry into the lock hash table to be waken up at unlock time.
> */
> -static void pv_kick_node(struct mcs_spinlock *node)
> +static void pv_scan_next(struct qspinlock *lock, struct mcs_spinlock *node)
I'm not too sure about that name change..
> {
>...
2015 Apr 07
0
[PATCH v15 13/15] pvqspinlock: Only kick CPU at unlock time
.... All these CPU kicking and halting (VMEXIT) can be expensive
and slow down system performance, especially in an overcommitted guest.
This patch add a new vCPU state (vcpu_hashed) which enables the code
to delay CPU kicking until at unlock time. Once this state is set,
the new lock holder will set _Q_SLOW_VAL and fill in the hash table
on behalf of the halted queue head vCPU.
Signed-off-by: Waiman Long <Waiman.Long at hp.com>
---
kernel/locking/qspinlock.c | 10 ++--
kernel/locking/qspinlock_paravirt.h | 76 +++++++++++++++++++++++++----------
2 files changed, 59 insertions(+), 27 d...
2015 Mar 18
2
[PATCH 8/9] qspinlock: Generic paravirt support
...== val
> + * pv_kick(cpu) -- wakes a suspended vcpu
> + *
> + * Using these we implement __pv_queue_spin_lock_slowpath() and
> + * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
> + * native_queue_spin_unlock().
> + */
> +
> +#define _Q_SLOW_VAL (2U<< _Q_LOCKED_OFFSET)
> +
> +enum vcpu_state {
> + vcpu_running = 0,
> + vcpu_halted,
> +};
> +
> +struct pv_node {
> + struct mcs_spinlock mcs;
> + struct mcs_spinlock __res[3];
> +
> + int cpu;
> + u8 state;
> +};
> +
> +/*
> + * Initia...
2015 Mar 18
2
[PATCH 8/9] qspinlock: Generic paravirt support
...== val
> + * pv_kick(cpu) -- wakes a suspended vcpu
> + *
> + * Using these we implement __pv_queue_spin_lock_slowpath() and
> + * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
> + * native_queue_spin_unlock().
> + */
> +
> +#define _Q_SLOW_VAL (2U<< _Q_LOCKED_OFFSET)
> +
> +enum vcpu_state {
> + vcpu_running = 0,
> + vcpu_halted,
> +};
> +
> +struct pv_node {
> + struct mcs_spinlock mcs;
> + struct mcs_spinlock __res[3];
> +
> + int cpu;
> + u8 state;
> +};
> +
> +/*
> + * Initia...
2015 Apr 09
0
[PATCH v15 09/15] pvqspinlock: Implement simple paravirt support for the qspinlock
...pu) -- wakes a suspended vcpu
>> + *
>> + * Using these we implement __pv_queue_spin_lock_slowpath() and
>> + * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
>> + * native_queue_spin_unlock().
>> + */
>> +
>> +#define _Q_SLOW_VAL (3U<< _Q_LOCKED_OFFSET)
>> +
>> +enum vcpu_state {
>> + vcpu_running = 0,
>> + vcpu_halted,
>> +};
>> +
>> +struct pv_node {
>> + struct mcs_spinlock mcs;
>> + struct mcs_spinlock __res[3];
>> +
>> + int cpu;
>> + u8...
2015 Mar 19
0
[PATCH 8/9] qspinlock: Generic paravirt support
...o done;
+ return;
cpu_relax();
}
- this_cpu_write(__pv_lock_wait, lock);
+ pv_set_head(lock, (struct pv_node *)node);
/*
- * __pv_lock_wait must be set before setting _Q_SLOW_VAL
- *
- * [S] __pv_lock_wait = lock [RmW] l = l->locked = 0
- * MB MB
- * [S] l->locked = _Q_SLOW_VAL [L] __pv_lock_wait
+ * The head must be set before we set _Q_SLOW_VAL such that...
2015 Mar 19
0
[PATCH 8/9] qspinlock: Generic paravirt support
...o done;
+ return;
cpu_relax();
}
- this_cpu_write(__pv_lock_wait, lock);
+ pv_set_head(lock, (struct pv_node *)node);
/*
- * __pv_lock_wait must be set before setting _Q_SLOW_VAL
- *
- * [S] __pv_lock_wait = lock [RmW] l = l->locked = 0
- * MB MB
- * [S] l->locked = _Q_SLOW_VAL [L] __pv_lock_wait
+ * The head must be set before we set _Q_SLOW_VAL such that...
2015 Apr 02
0
[PATCH 8/9] qspinlock: Generic paravirt support
...y.
> This will be bound in cost to the same number if probes we required for
> insertion and avoids the full array scan.
>
> Now I think we can indeed do this, if as said earlier we do not clear
> the bucket on insert if the cmpxchg succeeds, in that case the unlock
> will observe _Q_SLOW_VAL and do the lookup, the lookup will then find
> the entry. And we then need the unlock to clear the entry.
> _Q_SLOW_VAL
> Does that explain this? Or should I try again with code?
OK, I got your proposal now. However, there is still the issue that
setting the _Q_SLOW_VAL flag and the hash...
2015 Mar 16
0
[PATCH 8/9] qspinlock: Generic paravirt support
...tr, u8 val) -- suspends the vcpu if *ptr == val
+ * pv_kick(cpu) -- wakes a suspended vcpu
+ *
+ * Using these we implement __pv_queue_spin_lock_slowpath() and
+ * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
+ * native_queue_spin_unlock().
+ */
+
+#define _Q_SLOW_VAL (2U << _Q_LOCKED_OFFSET)
+
+enum vcpu_state {
+ vcpu_running = 0,
+ vcpu_halted,
+};
+
+struct pv_node {
+ struct mcs_spinlock mcs;
+ struct mcs_spinlock __res[3];
+
+ int cpu;
+ u8 state;
+};
+
+/*
+ * Initialize the PV part of the mcs_spinlock node.
+ */
+static void pv_init_node(struct...
2015 Mar 16
0
[PATCH 8/9] qspinlock: Generic paravirt support
...tr, u8 val) -- suspends the vcpu if *ptr == val
+ * pv_kick(cpu) -- wakes a suspended vcpu
+ *
+ * Using these we implement __pv_queue_spin_lock_slowpath() and
+ * __pv_queue_spin_unlock() to replace native_queue_spin_lock_slowpath() and
+ * native_queue_spin_unlock().
+ */
+
+#define _Q_SLOW_VAL (2U << _Q_LOCKED_OFFSET)
+
+enum vcpu_state {
+ vcpu_running = 0,
+ vcpu_halted,
+};
+
+struct pv_node {
+ struct mcs_spinlock mcs;
+ struct mcs_spinlock __res[3];
+
+ int cpu;
+ u8 state;
+};
+
+/*
+ * Initialize the PV part of the mcs_spinlock node.
+ */
+static void pv_init_node(struct...