[Qemu-devel] question about VM kernel parameter idle=<poll/mwait/halt/nomwait>

[Zhanghaoyu (A)]

Hi, all

What's the difference of the linux guest kernel parameter 
idle=<poll/mwait/halt/nomwait>, especially in performance?

Taking the performance into account, which one is best?

In my opinion, if the number of all VMs' vcpus is far more than that of pcpus, 
e.g. SPECVirt test, idle=halt is better for server's total throughput,
otherwise, e.g. in some CT scenario, the number of total vcpus is not greater 
than that of pcpus, idle=poll is better for server's total throughput,
because of less latency and VMEXIT.

linux-3.9 and above, idle=mwait is not recommended.

Thanks,
Zhang Haoyu