Re: [PATCH] tsc-disable_B9

From: Mikael Pettersson (
Date: Fri Aug 16 2002 - 08:19:31 EST

Alan Cox writes:
> On Thu, 2002-08-15 at 17:56, Andrea Arcangeli wrote:
> > sorry but I don't see the point of badtsc only in kernel.
> >
> > If the TSC is bad that will be in particular bad from userspace where
> > there's no hope to know what CPU you're running on.
> You can still do meaningful measurements for things like profiling
> because the cpu hop is statistically uninteresting.

There are kernel extensions around that handle process migration across
CPUs while providing virtualised per-process TSC counts, and for which
the TSCs do NOT need to be in perfect sync.

Disabling user-space RDTSC just because the TSCs aren't in sync is stupid.

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