[Xen-devel] determine the latency characteristics of a VM automatically

[David Xu <davidxu06@xxxxxxxxx>]

Hi George,

Tow months ago, we talked about how to reduce the scheduling latency for a specific VM which runs a mixed workload, where the boost mechanism can not works well. I have tried some methods to reduce the scheduling latency for some assumed latency-sensitive VMs and got some progress on it. Now I hope to make it on demand. That is to say, I hope to get the scheduler to determine the latency characteristics of a VM automatically. Since most time latency-sensitive operations are initiated with an interrupt, so a pending interrupt generally means that there is a latency sensitive operation waiting to happen. I remember you said your idea was to have the scheduler look at the historical rate of interrupts and determine a preemption timeslice based on those. I know your general idea, but could you talk more about it? What's more, I wonder if only the interrupts can infer the workload type? In my opinion, a pending interrupt indicates there is a operation to handle but may not be latency sensitive. Some common I/O operation, e.g. http request for a web page or  file transmission, would also result in pending interrupt if the destination VM does not get scheduled at the moment. But they are not latency sensitive. Of course, if we can directly get some important information for distinguishing the latency-sensitive workload from common workload, it is powerful and high efficient. I am looking forward to your opinions and I hope I will not disturb your work. Thanks.

Regards,

Cong

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