[Qemu-devel] [question] Is there a plan to introduce a unified co-scheduling mechanism to CFS ?

[Qemu-devel] [question] Is there a plan to introduce a unified co-scheduling mechanism to CFS ?

[Zhang Haoyu]

Hi,

Is it worthy to introduce a unified co-scheduling mechanism to CFS ?
Because multiple cooperating threads or tasks frequently synchronize 
with each other,
not executing them concurrently would only increase the latency of 
synchronization.
For example, a thread blocking in spinlock to waiting for another thread 
to release the same spinlock
might reduce its waiting time by being executed concurrently with the 
thread which hold the same spinlock.
In virtualization scenario, multiple vcpus (which belong to the same vm) 
co-scheduling is more desired
when several cooperating threads/task is running in guest.

Is there a plane for this work?

Thanks,
Zhang Haoyu

Re: [Qemu-devel] [question] Is there a plan to introduce a unified co-scheduling mechanism to CFS ?

[Wanpeng Li]

于 10/10/14, 7:37 PM, Zhang Haoyu 写道:
> Hi,
>
> Is it worthy to introduce a unified co-scheduling mechanism to CFS ?
> Because multiple cooperating threads or tasks frequently synchronize 
> with each other,
> not executing them concurrently would only increase the latency of 
> synchronization.
> For example, a thread blocking in spinlock to waiting for another 
> thread to release the same spinlock
> might reduce its waiting time by being executed concurrently with the 
> thread which hold the same spinlock.
> In virtualization scenario, multiple vcpus (which belong to the same 
> vm) co-scheduling is more desired
> when several cooperating threads/task is running in guest.
>
> Is there a plane for this work?

Please refer to gang scheduler.

Regards,
Wanpeng Li

>
> Thanks,
> Zhang Haoyu
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Re: [Qemu-devel] [question] Is there a plan to introduce a unified co-scheduling mechanism to CFS ?

[Zhang Haoyu]

 >> Hi,
 >>
 >> Is it worthy to introduce a unified co-scheduling mechanism to CFS ?
 >> Because multiple cooperating threads or tasks frequently synchronize 
with each other,
 >> not executing them concurrently would only increase the latency of 
synchronization.
 >> For example, a thread blocking in spinlock to waiting for another 
thread to release the same spinlock
 >> might reduce its waiting time by being executed concurrently with 
the thread which hold the same spinlock.
 >> In virtualization scenario, multiple vcpus (which belong to the same 
vm) co-scheduling is more desired
 >> when several cooperating threads/task is running in guest.
 >>
 >> Is there a plane for this work?
 >
 > Please refer to gang scheduler.
 >
Is there a mechanism to dynamically detect which vcpus belong to the 
same gang?
Maybe a cooperative degree can be used to decide the threshold of which 
vcpus belong to the same gang, just a wild thought.

 > Regards,
 > Wanpeng Li
 >>
 >> Thanks,
 >> Zhang Haoyu