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SubjectRe: [PATCH v2 0/4] implement vcpu preempted check
2016-07-06 18:44 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 06/07/2016 08:52, 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.
>>>
>>> test-case:
>>> 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?
>
> If it's just for spin loops, you can check if the version field in the
> steal time structure has changed.

Steal time will not be updated until ahead of next vmentry except
wrmsr MSR_KVM_STEAL_TIME. So it can't represent it is preempted
currently, right?

Regards,
Wanpeng Li

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