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

[Avi Kivity <avi@qumranet.com>]

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.