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On 07/01/2014 01:35 PM, Peter Zijlstra wrote: > On Sat, Jun 28, 2014 at 02:47:04PM +0530, Raghavendra K T wrote: >> In virtualized environment there are mainly three problems >> related to spinlocks that affects performance. >> 1. LHP (lock holder preemption) >> 2. Lock Waiter Preemption (LWP) >> 3. Starvation/fairness >> >> Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though >> pv-ticketlocks tried to address these problems we can further improve at the >> cost of...

On 07/01/2014 01:35 PM, Peter Zijlstra wrote: > On Sat, Jun 28, 2014 at 02:47:04PM +0530, Raghavendra K T wrote: >> In virtualized environment there are mainly three problems >> related to spinlocks that affects performance. >> 1. LHP (lock holder preemption) >> 2. Lock Waiter Preemption (LWP) >> 3. Starvation/fairness >> >> Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though >> pv-ticketlocks tried to address these problems we can further improve at the >> cost of...

In virtualized environment there are mainly three problems related to spinlocks that affects performance. 1. LHP (lock holder preemption) 2. Lock Waiter Preemption (LWP) 3. Starvation/fairness Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though pv-ticketlocks tried to address these problems we can further improve at the cost of relaxed fairness. The following patch tries to achiev...

In virtualized environment there are mainly three problems related to spinlocks that affects performance. 1. LHP (lock holder preemption) 2. Lock Waiter Preemption (LWP) 3. Starvation/fairness Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though pv-ticketlocks tried to address these problems we can further improve at the cost of relaxed fairness. The following patch tries to achiev...

On Wed, May 28, 2014 at 05:46:39PM +0530, Raghavendra K T wrote: > In virtualized environment there are mainly three problems > related to spinlocks that affect performance. > 1. LHP (lock holder preemption) > 2. Lock Waiter Preemption (LWP) > 3. Starvation/fairness > > Though ticketlocks solve the fairness problem, it worsens LWP, LHP problems. > pv-ticketlocks tried to address this. But we can further improve at the > cost of relaxed fairness. So I really...

On Sat, Jun 28, 2014 at 02:47:04PM +0530, Raghavendra K T wrote: > In virtualized environment there are mainly three problems > related to spinlocks that affects performance. > 1. LHP (lock holder preemption) > 2. Lock Waiter Preemption (LWP) > 3. Starvation/fairness > > Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though > pv-ticketlocks tried to address these problems we can further improve at the > cost of relaxed fairness. The f...

...30, Raghavendra K T wrote: > On 07/01/2014 01:35 PM, Peter Zijlstra wrote: > >On Sat, Jun 28, 2014 at 02:47:04PM +0530, Raghavendra K T wrote: > >>In virtualized environment there are mainly three problems > >>related to spinlocks that affects performance. > >>1. LHP (lock holder preemption) > >>2. Lock Waiter Preemption (LWP) > >>3. Starvation/fairness > >> > >>Though Ticketlocks solve fairness problem it worsens LWP, LHP problems. Though > >>pv-ticketlocks tried to address these problems we can further improve at t...

In virtualized environment there are mainly three problems related to spinlocks that affect performance. 1. LHP (lock holder preemption) 2. Lock Waiter Preemption (LWP) 3. Starvation/fairness Though ticketlocks solve the fairness problem, it worsens LWP, LHP problems. pv-ticketlocks tried to address this. But we can further improve at the cost of relaxed fairness. In this patch, we form a batch of eligibl...

In virtualized environment there are mainly three problems related to spinlocks that affect performance. 1. LHP (lock holder preemption) 2. Lock Waiter Preemption (LWP) 3. Starvation/fairness Though ticketlocks solve the fairness problem, it worsens LWP, LHP problems. pv-ticketlocks tried to address this. But we can further improve at the cost of relaxed fairness. In this patch, we form a batch of eligibl...

At the most recent Xen Summit, Thomas Friebel presented a paper ("Preventing Guests from Spinning Around", http://xen.org/files/xensummitboston08/LHP.pdf) investigating the interactions between spinlocks and virtual machines. Specifically, he looked at what happens when a lock-holding VCPU gets involuntarily preempted. The obvious first order effect is that while the VCPU is not running, the effective critical region time goes from being micro...

At the most recent Xen Summit, Thomas Friebel presented a paper ("Preventing Guests from Spinning Around", http://xen.org/files/xensummitboston08/LHP.pdf) investigating the interactions between spinlocks and virtual machines. Specifically, he looked at what happens when a lock-holding VCPU gets involuntarily preempted. The obvious first order effect is that while the VCPU is not running, the effective critical region time goes from being micro...

At the most recent Xen Summit, Thomas Friebel presented a paper ("Preventing Guests from Spinning Around", http://xen.org/files/xensummitboston08/LHP.pdf) investigating the interactions between spinlocks and virtual machines. Specifically, he looked at what happens when a lock-holding VCPU gets involuntarily preempted. The obvious first order effect is that while the VCPU is not running, the effective critical region time goes from being micro...

...tire timeslice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that's also a problem, but not catastrophic). (See Thomas Friebel's talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...tire timeslice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that's also a problem, but not catastrophic). (See Thomas Friebel's talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...tire timeslice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that's also a problem, but not catastrophic). (See Thomas Friebel's talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...lice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that''s also a problem, but not catastrophic). (See Thomas Friebel''s talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...lice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that''s also a problem, but not catastrophic). (See Thomas Friebel''s talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...lice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that''s also a problem, but not catastrophic). (See Thomas Friebel''s talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...tire timeslice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that's also a problem, but not catastrophic). (See Thomas Friebel's talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...

...tire timeslice spinning. (Note that this is not the same problem as lock-holder preemption, which this series also addresses; that's also a problem, but not catastrophic). (See Thomas Friebel's talk "Prevent Guests from Spinning Around" http://www.xen.org/files/xensummitboston08/LHP.pdf for more details.) Currently we deal with this by having PV spinlocks, which adds a layer of indirection in front of all the spinlock functions, and defining a completely new implementation for Xen (and for other pvops users, but there are none at present). PV ticketlocks keeps the existing t...