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Re: [Qemu-devel] question about VM kernel parameter idle=<poll/mwait/hal
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [Qemu-devel] question about VM kernel parameter idle=<poll/mwait/halt/nomwait> |
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Date: |
Thu, 21 Nov 2013 09:01:39 +0200 |
On Thu, Nov 21, 2013 at 03:45:28AM +0000, Zhanghaoyu (A) wrote:
> 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.
Makes sense overall.
> linux-3.9 and above, idle=mwait is not recommended.
>
> Thanks,
> Zhang Haoyu
Does it actually have effect? I didn't think it would.