Re: [Xen-devel] [RFC] Correct/fast timestamping in apps under Xen [1 of 4]: Reliable TSC

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 10/10/2009 06:55, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:

> The kernel does about between 400k and 1.4M/sec, median around ~600k,
> for a git pull (which I think is single-threaded), and about
> 200k-500k/sec for a kernel compile (-j4 on 2 vcpus).  Usermode is a much
> lower rate; around 1000/sec for the kernel compile.
> 
> Baseline idle is around 1000/sec kernel, 10/sec user.
> 
> Also, my inline naked rdtsc benchmark shows that the emulated rdtsc is
> taking around 465ns (vs 30, a 15x slowdown).

Hmmm... So at 600k/sec, the kernel spends an appreciable amount of time
(1-2%) doing RDTSCs? And with emulation that'll be more like 25-30%.

It's quite a surprisingly high rate.

 -- Keir



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