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Date: Tue, 19 Nov 2019 06:35:23 -0800
From: "Doug Smythies" <dsmythies@...us.net>
To: "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
"'Linux PM'" <linux-pm@...r.kernel.org>
Cc: "'Linux ACPI'" <linux-acpi@...r.kernel.org>,
"'LKML'" <linux-kernel@...r.kernel.org>,
"'Viresh Kumar'" <viresh.kumar@...aro.org>,
"'Sudeep Holla'" <sudeep.holla@....com>,
"'Dmitry Osipenko'" <digetx@...il.com>
Subject: RE: [RFT][PATCH 1/3] PM: QoS: Introduce frequency QoS
On 2019.11.17 08:13 Doug Smythies wrote:
> On 2019.11.16 23:35 Doug Smythies wrote:
>> Hi Rafael,
>>
>> Not sure, but I think it is this one that
>> causes complaining when I try to set the
>> intel_pstate driver to passive mode.
>> I started from active mode, powersave governor,
>> no HWP.
>>
>> Kernel: 5.4-rc7
>>
>> I did not go back and try previous 5.4 RCs.
After looking at the git tags for this patch,
I tried kernel 5.4-rc2, which was the closest
Kernel I had to before the patch set was added.
It worked fine, as expected.
>> I did try kernel 5.3-rc8, because I already had
>> it installed, and it worked fine.
>>
>> I use a script (for years), run as sudo:
>>
>> doug@s15:~/temp$ cat set_cpu_passive
>> #! /bin/bash
>> cat /sys/devices/system/cpu/intel_pstate/status
>> echo passive > /sys/devices/system/cpu/intel_pstate/status
>> cat /sys/devices/system/cpu/intel_pstate/status
>>
>> And I get this (very small excerpt):
>>
>> freq_qos_add_request() called for active request
>> WARNING: CPU: 1 PID: 2758 at kernel/power/qos.c:763 freq_qos_add_request+0x4c/0xa0
>> CPU: 1 PID: 2758 Comm: set_cpu_passive Not tainted 5.4.0-rc7-stock #727
>> Failed to add freq constraint for CPU0 (-22)
>>
>> freq_qos_add_request() called for active request
>> WARNING: CPU: 1 PID: 2758 at kernel/power/qos.c:763 freq_qos_add_request+0x4c/0xa0
>> CPU: 1 PID: 2758 Comm: set_cpu_passive Tainted: G W 5.4.0-rc7-stock #727
>> Failed to add freq constraint for CPU1 (-22)
Updated summary of previous emails:
This patch or patch set breaks the after boot
ability to change CPU frequency scaling drivers.
Using a workaround of booting with
"intel_pstate=passive" seems to prevent the errors.
Changing between the intel_pstate and intel_cpufreq drivers
(i.e. between active and passive modes)
after boot, either way, causes the errors. i.e.
Failed to add freq constraint for CPU7 (-22)
(2 per CPU per attempt)
This is 100% repeatable.
> I forgot to mention, other than the error messages,
> things seems to work fine.
Correction: It is actually quite bad. Eventually,
there will be a "Segmentation fault (core dumped)",
and then even re-boot gets stuck and the only
recourse seems to be the reset button.
This is not 100% repeatable.
I did this (kernel 5.4-rc8):
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 8ab3170..24c7a6b 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2491,6 +2491,8 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
{
int ret;
+ pr_info("Intel P-state register driver .... \n");
+
memset(&global, 0, sizeof(global));
global.max_perf_pct = 100;
@@ -2508,6 +2510,8 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
static int intel_pstate_unregister_driver(void)
{
+ pr_info("Intel P-state unregister driver .... \n");
+
if (hwp_active)
return -EBUSY;
And got this (dmesg | grep -i pstate):
[ 2.024876] intel_pstate: Intel P-state driver initializing
[ 2.024883] intel_pstate: Intel P-state register driver ....
Attempt to change from the booted passive mode to active mode:
[ 175.903031] intel_pstate: Intel P-state unregister driver ....
[ 175.975543] intel_pstate: Intel P-state register driver ....
[ 175.975754] intel_pstate_register_driver+0x4b/0x90
[ 175.975756] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.977728] intel_pstate_register_driver+0x4b/0x90
[ 175.977730] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.979644] intel_pstate_register_driver+0x4b/0x90
[ 175.979647] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.981424] intel_pstate_register_driver+0x4b/0x90
[ 175.981427] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.982428] intel_pstate_register_driver+0x4b/0x90
[ 175.982430] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.983127] intel_pstate_register_driver+0x4b/0x90
[ 175.983128] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.983829] intel_pstate_register_driver+0x4b/0x90
[ 175.983832] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.984434] intel_pstate_register_driver+0x4b/0x90
[ 175.984435] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.985040] intel_pstate_register_driver+0x4b/0x90
[ 175.985041] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.985598] intel_pstate_register_driver+0x4b/0x90
[ 175.985600] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.986178] intel_pstate_register_driver+0x4b/0x90
[ 175.986179] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.986721] intel_pstate_register_driver+0x4b/0x90
[ 175.986723] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.987301] intel_pstate_register_driver+0x4b/0x90
[ 175.987302] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.987828] intel_pstate_register_driver+0x4b/0x90
[ 175.987830] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.988420] intel_pstate_register_driver+0x4b/0x90
[ 175.988421] ? intel_pstate_unregister_driver+0x31/0x40
[ 175.988920] intel_pstate_register_driver+0x4b/0x90
[ 175.988921] ? intel_pstate_unregister_driver+0x31/0x40
Sometimes I get this:
grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:42
Instead of this:
grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:42
/sys/devices/system/cpu/intel_pstate/no_turbo:0
/sys/devices/system/cpu/intel_pstate/num_pstates:23
/sys/devices/system/cpu/intel_pstate/status:active
/sys/devices/system/cpu/intel_pstate/turbo_pct:18
But do not yet know the exact way to reliably
create it.
This is as far as I got so far.
... Doug
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