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SubjectRe: [RFC][PATCH] Runtime switching of the idle function [take 2]
Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Mon, 2005-11-28 at 19:02 -0800, Andrew Morton wrote:
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> > >
> > > This patch creates a directory in /sys/kernel called idle.
> > >
> >
> > At no point do you appear to explain _why_ the kernel needs this feature?
>
> Sorry about that. This originally came up when we had problems with the
> AMD64 x2 in the -rt patch. It was noted that the TSCs would get very
> far out of sync and cause problems.

Unsynced TSCs are rare, but they happen. I guess even if we were to resync
them, these measurements would screw up.


> The way to solve this was to set
> idle=poll. The original patch I sent was to allow the user to change to
> idle=poll dynamically. This way they could switch to the poll_idle and
> run there tests (requiring tsc not to drift) and then switch back to the
> default idle to save on electricity.

Use gettimeofday()?

If it's just for some sort of instrumentation, run NR_CPUS instances of a
niced-down busyloop, pin each one to a different CPU? That way the idle
function doesn't get called at all..

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