Re: [RT] read_tsc: ACK! TSC went backward! Unsynced TSCs?

Dave Jones
2005-11-28T18:31:19Z

On Mon, Nov 28, 2005 at 12:39:28PM -0500, Lee Revell wrote:
> On Mon, 2005-11-28 at 09:30 -0800, thockin@hockin.org wrote:
> > The kernel's use of TSC is wholly incorrect. TSCs can ramp up and
> > down and *do* vary between nodes as well as between cores within a
> > node. You really can not compare TSCs between cpu cores at all, as is
> > (and the kernel assumes 1 global TSC in at least a few places).
>
> That's one way to look at it; another is that the AMD dual cores have a
> broken TSC implementation. The kernel's use of the TSC was never a
> problem in the past...

Not true. Speedstep, or anything else that uses SMI to disappear
into magick bios code for long periods of time also have exactly
the same issue.

This is not a new problem.

Dave