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

From: Matthew Kent
Subject: [Qemu-devel] Re: [kvm-devel] [PATCH/RFC 4/4] Add support for dynamic ticks.
Date: Fri, 17 Aug 2007 00:16:09 -0700 (PDT)
User-agent: SquirrelMail/1.4.9a

> 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 <address@hidden>
> Signed-off-by: Luca Tettamanti <address@hidden>

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:

address@hidden ~]$ 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.
Matthew Kent <address@hidden>

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