Re: [ck] [ANNOUNCE] Interbench 0.27

[Con Kolivas <kernel@kolivas.org>]

On Sat, 6 Aug 2005 13:37, Gabriel Devenyi wrote:
> After conducting some further research I've determined that cool n quiet
> has no effect on this "bug" if you can call it that. With the system
> running in init 1, and cool n quiet disabled in the bios, a sleep(N>0)
> results in the run_time value afterwards always being nearly the same value
> of ~995000 on my athlon64, similarly, my server an athlon-tbird, which
> definitely has no power saving features, hovers at ~1496000

We know that sleep(1) doesn't give us accurate sleep of 1 second, only close 
to it limited by Hz, schedule_timeout and how busy the kernel otherwise is.

> Obviously since these values are nowhere near 10000, the loops_per_ms
> benchmark runs forever, has anyone seen/read about sleep on amd machines
> doing something odd? Can anyone else with an amd machine confirm this
> behavior? Con: should we attempt to get the attention of LKML to see why
> amd chips act differently?

None of that matters because the timing is done during a non sleep period 
using the real time clock:

	start_time = get_nsecs(&myts);
	burn_loops(loops);
	run_time = get_nsecs(&myts) - start_time;

So the time spent in sleep(1) should be irrelevant to the timing of 
loops_per_ms. Something else is happening to the cpu _during_ the sleep that 
makes the next lot of loops take a different length of time. That's the bit I 
haven't been able to figure out.

Cheers,
Con
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