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Re: [PATCH RFC v2 5/5] x86/mwait-idle: squash stats update when not actually entering C-state
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Fri, 21 Jan 2022 10:32:07 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Thu, Jan 20, 2022 at 05:21:31PM +0100, Jan Beulich wrote:
> On 20.01.2022 17:00, Roger Pau Monné wrote:
> > On Thu, Jan 20, 2022 at 03:05:12PM +0100, Jan Beulich wrote:
> >> While we don't want to skip calling update_idle_stats(), arrange for it
> >> to not increment the overall time spent in the state we didn't really
> >> enter.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> ---
> >> RFC: Arguably more of what follows could be moved into the if() -
> >> thoughts?
> >
> > I would move at least the restoring of the TSC, but I would be fine
> > with moving everything up to local_irq_enable unless I'm missing
> > something.
>
> Yes, that's what I was considering.
>
> > I think you could likely also avoid the call to update_idle_stats so
> > there's no need to fetch the new tick count.
>
> No, this call cannot be bypassed. At least not without further
> rearrangements elsewhere.
Ack, I would move everything you can then.
Thanks, Roger.
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