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Re: [PATCH RFC v2 5/5] x86/mwait-idle: squash stats update when not actually entering C-state
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 20 Jan 2022 17:21:31 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Thu, 20 Jan 2022 16:21:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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.
Jan
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