Re: [RFC][PATCH] Runtime switching of the idle function [take 2]

[Lee Revell <rlrevell@joe-job.com>]

On Wed, 2005-11-30 at 02:06 +0100, Andi Kleen wrote:
> > But on my system gettimeofday uses the TSC and it's still ~35x slower
> > than RDTSC:
> > 
> > rlrevell@mindpipe:~$ ./timetest 
> > rdtsc: 10000 calls in 1079 usecs
> > gettimeofday: 10000 calls in 36628 usecs
> 
> First if you run this on an Athlon 64 the measurement is likely
> wrong because RDTSC can be speculated around. To get accurate
> data you need to add synchronizing instructions.
> 

OK.  Just for reference here's what people on the JACK list reported:

2.6.14-rt13, PREEMPT_RT, Athlon X2 4400+ (dual core)

rdtsc: 10000 calls in 68 usecs
gettimeofday: 10000 calls in 5170 usecs

P4@3.3Ghz/HT (OpenSUSE 10.0 2.6.13-15-smp):

rdtsc: 10000 calls in 253 usecs
gettimeofday: 10000 calls in 26547 usecs

> Then you're likely running 32bit. It doesn't use vsyscall gettimeofday
> yet, which makes it slower. 64bit would.

Yes, I am.  So it sounds like vsyscall gettimeofday for i386 is in the
works?

Lee

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