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Groups > linux.kernel > #1647760
| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems |
| Date | 2017-05-23 10:00 +0200 |
| Message-ID | <tKcTx-a4-37@gated-at.bofh.it> (permalink) |
| References | <tJYnx-80c-51@gated-at.bofh.it> <tJYnw-80c-49@gated-at.bofh.it> <tK27M-1Q5-17@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, May 22, 2017 at 08:20:56PM +0000, Ghannam, Yazen wrote:
> On the other hand, MWAIT on AMD limits the hardware to using only certain,
> shallower Cstates. This is okay if we define individual states and use MWAIT
> for some of them. But it would consume more power if used always.
Let me see if I understand it correctly:
Even though we used to do HLT on previous families as idling with HLT
*is* the preferred method until now, with your change you're moving
*every* AMD machine out there to do MWAIT now.
Lemme look at the F15h BKDG:
"2.5.3.2
C-state Request Interface
C-states are dynamically requested by software and are exposed through
ACPI objects (see 2.5.3.6 [ACPI Processor C-state Objects]). C-states
can be requested on a per-core basis. Software requests a C-state change
in one of two ways, either by executing the HLT instruction or by
reading from an IO address specified by MSRC001_0073[CstateAddr] plus an
offset of 0 through 7 (see D18F4x11[C:8])."
So this doesn't say anything about using MWAIT.
What's up?
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
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Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems Borislav Petkov <bp@alien8.de> - 2017-05-22 18:30 +0200
RE: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems "Ghannam, Yazen" <Yazen.Ghannam@amd.com> - 2017-05-22 22:30 +0200
Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems Borislav Petkov <bp@alien8.de> - 2017-05-23 10:00 +0200
RE: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems "Ghannam, Yazen" <Yazen.Ghannam@amd.com> - 2017-05-23 15:00 +0200
Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems Borislav Petkov <bp@alien8.de> - 2017-05-23 15:10 +0200
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