[PATCH v2 0/4] implement vcpu preempted check
waiman.long at hpe.com
Tue Jul 12 01:10:15 AEST 2016
On 07/06/2016 02:52 AM, Peter Zijlstra wrote:
> On Tue, Jun 28, 2016 at 10:43:07AM -0400, Pan Xinhui wrote:
>> change fomr v1:
>> a simplier definition of default vcpu_is_preempted
>> skip mahcine type check on ppc, and add config. remove dedicated macro.
>> add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner.
>> add more comments
>> thanks boqun and Peter's suggestion.
>> This patch set aims to fix lock holder preemption issues.
>> perf record -a perf bench sched messaging -g 400 -p&& perf report
>> 18.09% sched-messaging [kernel.vmlinux] [k] osq_lock
>> 12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner
>> 5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock
>> 3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task
>> 3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq
>> 3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is
>> 2.49% sched-messaging [kernel.vmlinux] [k] system_call
>> We introduce interface bool vcpu_is_preempted(int cpu) and use it in some spin
>> loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner.
>> These spin_on_onwer variant also cause rcu stall before we apply this patch set
> Paolo, could you help out with an (x86) KVM interface for this?
> Waiman, could you see if you can utilize this to get rid of the
> SPIN_THRESHOLD in qspinlock_paravirt?
That API is certainly useful to make the paravirt spinlock perform
better. However, I am not sure if we can completely get rid of the
SPIN_THRESHOLD at this point. It is not just the kvm, the xen code need
to be modified as well.
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