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Re: Xen C-state Issues
- To: Elliott Mitchell <ehem+xen@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 23 Aug 2021 09:12:52 +0200
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- Delivery-date: Mon, 23 Aug 2021 07:13:03 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 21.08.2021 18:25, Elliott Mitchell wrote:
> ACPI C-state support might not see too much use, but it does see some.
>
> With Xen 4.11 and Linux kernel 4.19, I found higher C-states only got
> enabled for physical cores for which Domain 0 had a corresponding vCPU.
> On a machine where Domain 0 has 5 vCPUs, but 8 reported cores, the
> additional C-states would only be enabled on cores 0-4.
>
> This can be worked around by giving Domain 0 vCPUs equal to cores, but
> then offlining the extra vCPUs. I'm guessing this is a bug with the
> Linux 4.19 xen_acpi_processor module.
>
>
>
> Appears Xen 4.14 doesn't work at all with Linux kernel 4.19's ACPI
> C-state support. This combination is unable to enable higher C-states
> on any core. Since Xen 4.14 and Linux 4.19 are *both* *presently*
> supported it seems patch(es) are needed somewhere for this combination.
Hmm, having had observed the same quite some time ago, I thought I had
dealt with these problems. Albeit surely not in Xen 4.11 or Linux 4.19.
Any chance you could check up-to-date versions of both Xen and Linux
(together)?
Jan
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