Re: [Lcd4linux-devel] rdtscl() on i386

[Michael R. <re...@eu...>]

Hi Bernhard,

> following kernel commit has removed rdtcl() from being exported in
> userspace. It=92s now inside __KERNEL__ ifdef.
>=20
> Therefore, checking if <asm/msr.h> exists is not sufficient any more. r=
dtscl()
> is also problematic on multi-core systems. I guess it's time to get rid=
 of
> rdtscl() ...

I agree, especially for another reason: rdtsc() is problematic with=20
power-saving by CPU frequency scaling...

But what to use else? There's a fallback to a gettimeofday() busy loop;=20
but this loop is quite ressource-intensive...

Is there by any chance a senseful possibility to get small delays=20
(without reschedule) in userspace?

udelay() and friends would work, but only if changing the scheduler to=20
SCHED_RT (which is what I definitely do *not* like)


Any hints would be greatly appreciated!


TIA, Michael

--=20
Michael Reinelt <re...@eu...>
http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
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