Re: [PATCH 0/4] Rework alarm timer infrastrucure - take2

Avi Kivity
2007-08-22T16:45:00Z

Luca wrote:
>>> This is QEMU, with dynticks and HPET:
>>>
>>> % time seconds usecs/call calls errors syscall
>>> ------ ----------- ----------- --------- --------- ----------------
>>> 52.10 0.002966 0 96840 clock_gettime
>>> 19.50 0.001110 0 37050 timer_gettime
>>> 10.66 0.000607 0 20086 timer_settime
>>> 10.40 0.000592 0 8985 2539 sigreturn
>>> 4.94 0.000281 0 8361 2485 select
>>> 2.41 0.000137 0 8362 gettimeofday
>>> ------ ----------- ----------- --------- --------- ----------------
>>> 100.00 0.005693 179684 5024 total
>>>
>>>
>> This looks like 250 Hz?
>>
>
> Nope:
>
> # CONFIG_NO_HZ is not set
> # CONFIG_HZ_100 is not set
> # CONFIG_HZ_250 is not set
> # CONFIG_HZ_300 is not set
> CONFIG_HZ_1000=y
> CONFIG_HZ=1000
>
> and I'm reading it from /proc/config.gz on the guest.
>

Yeah, thought so -- so dyntick is broken at present.

Or maybe your host kernel can't support such a high rate. Probably
needs hrtimers or qemu dyntick over hpet oneshot support.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.