Re: Is guest OS oriented scheduling welcome?

[Anthony Liguori <anthony@codemonkey.ws>]

刘志建 wrote:
> Hello folks,
> In the past, it was said KVM would like to treat the guest OS threads differently in scheduling. However, till now, the qemu thread is regarded as a conventional user thread. Therefore, it is hard to control how much CPU slices one guest OS can utilize. I don't think a computing cloud provider likes this idea.
> And, what's more, "Xen and Co.: Communication-aware CPU Scheduling for Consolidated Xen-based Hosting Platforms"(http://www.cse.psu.edu/~sgovinda/papers/vee07.pdf) has shown that the standard thread scheduling in Linux might not fit the virtualization environment well.

By standard thread scheduling, I presume you mean scheduling that 
doesn't take into account IO?  That is, this paper is arguing that in a 
virtualization environment, you want to provide temporary 
disproportionate scheduling to favor IO bound workloads over CPU bound 
workloads.

I don't think you need the credit scheduler to implement this idea in 
KVM.  CFS provides a number of tunables to userspace along with pretty 
fine grain control ala cgroups.  I think that provides you a roughly 
equivalent interface to userspace that could be used to make scheduling 
adjustments based on IO consumption.

What are the other motivating factors for wanting to use credit over cfs?

Regards,

Anthony Liguori