On 2020.08.01 16:41 Srinivas Pandruvada wrote:

On Tue, 2020-07-28 at 17:13 +0200, Rafael J. Wysocki wrote:

quoted

From: Rafael J. Wysocki <redacted>

Allow intel_pstate to work in the passive mode with HWP enabled and
make it set the HWP minimum performance limit (HWP floor) to the
P-state value given by the target frequency supplied by the cpufreq
governor, so as to prevent the HWP algorithm and the CPU scheduler
from working against each other, at least when the schedutil governor
is in use, and update the intel_pstate documentation accordingly.

Among other things, this allows utilization clamps to be taken
into account, at least to a certain extent, when intel_pstate is
in use and makes it more likely that sufficient capacity for
deadline tasks will be provided.

After this change, the resulting behavior of an HWP system with
intel_pstate in the passive mode should be close to the behavior
of the analogous non-HWP system with intel_pstate in the passive
mode, except that in the frequency range below the base frequency
(ie. the frequency retured by the base_frequency cpufreq attribute
in sysfs on HWP systems) the HWP algorithm is allowed to go above
the floor P-state set by intel_pstate with or without hardware
coordination of P-states among CPUs in the same package.

Do you mean HWP.req.min will be below base_freq (unless user overrides
it)?

No.

With busy workload I see HWP req.min = HWP req.max.
The base freq: 1.3GHz (ratio 0x0d), MAX 1C turbo: 3.9GHz (ratio: 0x27)
When I monitor MSR 0x774 (HWP_REQ), I see
0x80002727

Yes, that is what I expect to see.

Normally msr 0x774
0x80002704

That would be "active" mode and the powersave governor, correct?.
And yes that is what I expect for your processor.
For mine, load or no load, decoded:
0x774: IA32_HWP_REQUEST:    CPU 0-5 :
    raw: 80002E08 : 80002E08 : 80002E08 : 80002E08 : 80002E08 : 80002E08 :
    min:        8 :        8 :        8 :        8 :        8 :        8 :
    max:       46 :       46 :       46 :       46 :       46 :       46 :
    des:        0 :        0 :        0 :        0 :        0 :        0 :
    epp:      128 :      128 :      128 :      128 :      128 :      128 :
    act:        0 :        0 :        0 :        0 :        0 :        0 :

This thread is about passive mode, and myself, I do not expect the last byte to be
4 (8 for mine) under load.

... Doug