Re: [Xen-devel] [PATCH] TSC scaling for live migration between platforms with different TSC frequecies

[John Levon <levon@xxxxxxxxxxxxxxxxx>]

On Fri, Jun 19, 2009 at 09:21:55AM +0800, Zhang, Xiantao wrote:

> > No. That's CPU0 only ('cpu == 0'). Solaris only has one system-wide
> > timer tick. This is mstate accounting: every kernel/user boundary,
> > every interrupt, etc. incurs at least one TSC read. (And of course
> > the machine is idle.)
> 
> So the rdtsc rate in the system is 2779.8/s per your testing ?

No the rdtsc rate on a single CPU on an idle system on one mache was
around that :)

> If so, the performance impact can be ignored. We had done the
> performance testing with sysbench oltp, and in the testing the rdtsc
> rate exceeds 120000 rdtsc/sec, but even in such extreme case
> perfomrance loss is still less 10%.  In addition, we also measured the
> emulation cost, and the result showes rdtsc can be done in 1500-1800
> cycles in emulation case.

It would be really good to see some Solaris perf results.

regards
john

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