ppc64_cpu @ Power9 - power mode changes

[Pitterling]

Power modes @ Power9 have changed:

• None
• Static Power Saver Mode
• Dynamic Performance Mode
• Maximum Performance Mode

ppc64_cpu currently reports:

• Dynamic, Favor Performance
• None
• Static
• Dynamic, Favor Power

[tyreld]

Is this documented somewhere? We've run across this before where the meaning of the mode values has been changed from what is architected in PAPR.

[Pitterling]

Kindly refer to IBM’s EnergyScale documentation for this at https://www.ibm.com/downloads/cas/6GZMODN3.

[Pitterling]

Any update here?

[tyreld]

This is a little frustrating on our end. While the names are documented in each new processor power scale document its not really properly defined anywhere and now instead of expanding the reversed space of available bit fields to add new energy management name definitions we keep using the same 4 energy managment minor codes and changing the names with each processor iteration.

We use the H_GET_EM_PARAMS hypercall in the kernel to get the status codes for the platform, group, pool, partition where each of these is a 2 byte code.

Status Codes (bit offset within 2 byte field): Bits 0:5 Reserved (zero)

Bits 6:8 Energy Management major code:

• 0b000: Non – floor modes:
• Bits 9:15 Energy Management minor code:
• • 0x00: The energy management policy for this aggregation level is not specified.
• • 0x01: Maximum Performance (Energy Management enabled – performance may exceed nominal)
• • 0x02: Nominal Performance (Energy Management Disabled)
• • 0x03: Static Power Saving Mode
• • 0x04: Deterministic Performance (Energy Management enabled – consistent performance on a given work-
• • load independent of environmental factors and component variances)
• • 0x05 – 0x7F Reserved
• 0b001: Dynamic Power Management:
• • Bits 9:15 Performance floor as a percentage of nominal (0% - 100%).
• 0b010:0b111 Reserved

[tyreld]

The existing interface is being replaced with Power 10. Here is the pull request for reference: #68

For previous processors that use the H_GET_EM_PARAMS call we will have to determine the processor type to map to the correct power mode names.

[Pitterling]

https://github.com/pratiksampat/powerpc-utils/blob/H_GET_ENERGY_SCALE_INFO_v2/src/ppc64_cpu.c

is doing the same wrong mapping as this is just a copy of the current code ..

[Pitterling]

@tyreld I try to tie the provided information - current coding and your comment above about P9

P8 - from coding

# 0x0001: "Dynamic, Favor Performance"
# 0x0002: "None"
# 0x0003: "Static"
# 0x00ff: "Dynamic, Favor Power"
# default: "Unknown"

P9 - from your information above

# 0x0001: "Maximum Performance"
# 0x0002: "Nominal Performance (None)"
# 0x0003: "Static Power Saving"
# 0x0004: "Dynamic Performance"
# default: "Unknown"

Is my understanding correct?
So the changes are actually the naming for 0x0001 -> Dynamic,Favor Performance --> Maximum Performance
and 0x00ff has been discarded, but 0x0004 has been added ?

Thx