qemu cpu utility too high as dom0 cpu stealtime's also high

qemu cpu utility too high as dom0 cpu stealtime's also high

[alice wan]

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hi all,

       when i started 10 windows vms of 4 vcpu on the host with 8 cpu, dom0
has 4 shareble vcpu, i found qemu-dm cpu utility is too high, about 80-90%,
lasting for more than half an hour. after a long period of time, the dom0
became normal.

        i observed that when qemu-dm %cpu's too high, the dom0 cpu's
stealtime was also too high.
        when dom0 became normal, %st  and qemu %cpu also became low.

        high stealtime is reasonable as the cpu is too busy, the time vcpu
wait for cpu scheduling  is too long.

        however, qemu high cpu utility is unreasonable,  the oprofile report
of qemu seems normal.

        I doubt the granularity of task cpu time accounting seems too rough.

        It seems that task cpu accounting didn't distinguish virtual cpu
time from cpu time so that  the qemu-dm cpu time = real cpu time+steal time

        Does the task cpu accounting is based on tick?

        the config about accounting 's like this:
        CONFIG_TASK_IO_ACCOUNTING=y
        # CONFIG_IRQ_TIME_ACCOUNTING is not set

        Should i turn on the CONFIG_IRQ_TIME_ACCOUNTING ?

        Any advice is appreciated, thanks in advance.

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