[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

From: Jamie Lokier
Subject: Re: [kvm-devel] [Qemu-devel] Re: [PATCH 0/4] Rework alarm timer infrastrucure - take2
Date: Sun, 19 Aug 2007 18:15:45 +0100
User-agent: Mutt/1.4.1i

Paul Brook wrote:
> > Yes, good thinking, but this should only be done if it actually impacts
> > something.  Reducing overhead from 0.1% to 0.05% is not worthwhile if it
> > introduces extra complexity.
> If the overhead is that small, why are we touching this code in the first 
> place?


A benchmark result was posted which is rather interesting:

>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 :)

I am surprised if 1000 redundant SIGALRMs per second is really causing
70% overhead in normal qemu execution, except on a rather old or slow
machine where signal delivery is very slow.

It would be good to understand the cause of that benchmark result.

-- Jamie

reply via email to

[Prev in Thread] Current Thread [Next in Thread]