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Re: [PATCH 3/5] x86/mwait-idle: update ICX C6 data
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 18 Jan 2022 15:08:29 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Tue, 18 Jan 2022 14:08:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.01.2022 11:20, Roger Pau Monné wrote:
> On Mon, Sep 06, 2021 at 03:01:12PM +0200, Jan Beulich wrote:
>> From: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
>>
>> Change IceLake Xeon C6 latency from 128 us to 170 us. The latency
>> was measured with the "wult" tool and corresponds to the 99.99th
>> percentile when measuring with the "nic" method. Note, the 128 us
>> figure correspond to the median latency, but in intel_idle we use
>> the "worst case" latency figure instead.
>>
>> C6 target residency was increased from 384 us to 600 us, which may
>> result in less C6 residency in some workloads. This value was tested
>> and compared to values 384, and 1000. Value 600 is a reasonable
>> tradeoff between power and performance.
>>
>> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
>> Acked-by: Zhang Rui <rui.zhang@xxxxxxxxx>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>> [Linux commit: d484b8bfc6fa71a088e4ac85d9ce11aa0385867e]
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks.
> AFAICT those values are all from measurements, and not in any manual
> or specification?
That's my understanding of the description, yes.
Jan
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