[Qemu-devel] Re: [kvm-devel] [PATCH/RFC 4/4] Add support for dynamic ticks.

[Avi Kivity <avi@qumranet.com>]

Matthew Kent wrote:
>> If DYNAMIC_TICKS is defined qemu does not attepmt to generate SIGALRM at a
>> constant rate. Rather, the system timer is set to generate SIGALRM only
>> when it is needed. DYNAMIC_TICKS reduces the number of SIGALRMs sent to
>> idle dynamic-ticked guests.
>> Original patch from Dan Kenigsberg <dank@qumranet.com>
>>
>> Signed-off-by: Luca Tettamanti <kronos.it@gmail.com>
>>     
>
> Wow, this patch sure made a difference for some timings I've been doing
> with kvm-35 and hackbench. All tests using 2.6.23-rc3+hrtimers patch for
> x86_64/i386 tickless and a quad core intel:
>
> [mkent@localhost ~]$ time ./hackbench 50
> x86_64 host                 : real 0m10.845s
> x86_64 host, bound to 1 cpu : real 0m21.884s
> i386 guest+unix clock       : real 0m49.206s
> i386 guest+hpet clock       : real 0m48.292s
> i386 guest+dynticks clock   : real 0m28.835s
>
> Results are repeatable and verfied with a stopwatch because I didn't
> believe them at first :)
>
> Great stuff.
>   

I'm not sure what these results mean...


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