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From: "Doug Smythies" <dsmythies@telus.net>
To: "'Srinivas Pandruvada'" <srinivas.pandruvada@linux.intel.com>
Cc: "'Linux Documentation'" <linux-doc@vger.kernel.org>,
	"'LKML'" <linux-kernel@vger.kernel.org>,
	"'Peter Zijlstra'" <peterz@infradead.org>,
	"'Giovanni Gherdovich'" <ggherdovich@suse.cz>,
	"'Francisco Jerez'" <francisco.jerez.plata@intel.com>,
	"'Linux PM'" <linux-pm@vger.kernel.org>,
	"'Rafael J. Wysocki'" <rjw@rjwysocki.net>
Subject: RE: [PATCH v4 2/2] cpufreq: intel_pstate: Implement passive mode with HWP enabled
Date: Sun, 2 Aug 2020 07:14:36 -0700
Message-ID: <000401d668d7$426d8760$c7489620$@net> (raw)
In-Reply-To: <0fad4951dbd0143b43d4ec7b0dcab6787e0c7a97.camel@linux.intel.com>

On 2020.08.01 16:41 Srinivas Pandruvada wrote:
> On Tue, 2020-07-28 at 17:13 +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > 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



  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-16 17:37 [PATCH v2 0/2] " Rafael J. Wysocki
2020-07-16 17:38 ` [PATCH v2 1/2] cpufreq: intel_pstate: Rearrange the storing of newv EPP values Rafael J. Wysocki
2020-07-16 17:42 ` [PATCH v2 2/2] cpufreq: intel_pstate: Implement passive mode with HWP enabled Rafael J. Wysocki
2020-07-27 15:13 ` [PATCH v3 0/2] " Rafael J. Wysocki
2020-07-27 15:15   ` [PATCH v3 1/2] cpufreq: intel_pstate: Rearrange the storing of new EPP values Rafael J. Wysocki
2020-07-27 15:17   ` [PATCH v3 2/2] cpufreq: intel_pstate: Implement passive mode with HWP enabled Rafael J. Wysocki
2020-07-28 15:09   ` [PATCH v4 0/2] " Rafael J. Wysocki
2020-07-28 15:11     ` [PATCH v4 1/2] cpufreq: intel_pstate: Rearrange the storing of new EPP values Rafael J. Wysocki
2020-07-30  1:31       ` Francisco Jerez
2020-07-28 15:13     ` [PATCH v4 2/2] cpufreq: intel_pstate: Implement passive mode with HWP enabled Rafael J. Wysocki
2020-08-01 23:21       ` Srinivas Pandruvada
2020-08-02 14:14         ` Doug Smythies [this message]
2020-08-02 19:20           ` Srinivas Pandruvada
2020-08-03 17:17       ` [PATCH v5] " Rafael J. Wysocki
2020-08-01 16:39     ` [PATCH v4 0/2] " Srinivas Pandruvada
2020-08-02 14:00       ` Doug Smythies
2020-08-02 18:39         ` Srinivas Pandruvada
2020-08-03  0:26           ` Doug Smythies
2020-08-03 17:23       ` Rafael J. Wysocki
2020-08-04 15:10   ` [PATCH v6] " Rafael J. Wysocki
2020-08-04 17:04     ` Doug Smythies
2020-08-05  9:34       ` Rafael J. Wysocki
2020-08-05 15:38         ` Srinivas Pandruvada
2020-08-05 16:28           ` Rafael J. Wysocki
2020-08-05 16:55   ` [PATCH v7] " Rafael J. Wysocki
2020-08-06  5:55     ` Doug Smythies
2020-08-06 11:25       ` Rafael J. Wysocki
2020-08-06 12:03     ` Rafael J. Wysocki
2020-08-10  0:44       ` Srinivas Pandruvada

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