[Bug 194963] New: schedutil governor causes audio problem in game

[Bug 194963] New: schedutil governor causes audio problem in game

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https://bugzilla.kernel.org/show_bug.cgi?id=194963

            Bug ID: 194963
           Summary: schedutil governor causes audio problem in game
           Product: Power Management
           Version: 2.5
    Kernel Version: 4.10.4
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: cpufreq
          Assignee: linux-pm@vger.kernel.org
          Reporter: john.ettedgui@gmail.com
        Regression: No

Created attachment 255443
  --> https://bugzilla.kernel.org/attachment.cgi?id=255443&action=edit
dmesg

Hello,

I'm on the kernel 4.10.4 but I've had the same issues for a few weeks already,
definitely on .3 and probably on .2 but not sure anymore.

When I switched the cpu governor from ondemand or performance to schedutil, it
all seemed fine, but actually playing a game in wine gives me audio cracking
every now and then, fairly similarly to when we didn't have a pulseaudio
backend in wine. (I have not tried using only alsa).

Interestingly I've tried 2 different games in Wine and the problem only happens
with one, I assume the more CPU intensive one: StarCraft 2.

Restarting the computer, killing pulseaudio and restarting it, limiting the
apps opened, not of that changed anything, but switching the governor back
fixed it right away.

My CPU is an Intel i7 4790k, this is my kernel line:
linux   /vmlinuz-linux root=/dev/sda3 rw  rootfstype=btrfs raid=noautodetect
intel_iommu=on quiet add_efi_memmap clocksource=hpet hpet=enable splash
consoleblank=0 intel_pstate=disable sysrq_always_enabled=1


I am not sure what else to provide, there was nothing in dmesg that seemed
related, nor any error in Wine, please tell me how I can help.

Thank you,
John

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[Bug 194963] schedutil governor causes audio problem in game

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--- Comment #1 from John (john.ettedgui@gmail.com) ---
I just tried a few more tests:

1) pstate's powersave: no issue (but it also doesn't scale for me...)

2) cpufreq's powersave: I have more the issue than not (in my original posting
it was maybe once every 2 seconds or so, in this case it's much more frequent).

3) cpufreq's conservative: better than powersave but still no good.

4) cpufreq's ondemand: all good as expected.

Based on that I'm guessing it's scaling related.

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[Bug 194963] schedutil governor causes audio problem in game

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Viresh Kumar (viresh.kumar@linaro.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |viresh.kumar@linaro.org

--- Comment #2 from Viresh Kumar (viresh.kumar@linaro.org) ---
John,

Can you please give us the value of 
/sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us

?

Try making this around 10000 (10ms). This is how frequently we try to change
the frequency and lowering it will make us more aggressive.

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[Bug 194963] schedutil governor causes audio problem in game

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |NEEDINFO
                 CC|                            |rjw@rjwysocki.net

--- Comment #3 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
It also would be good to test this patch:

https://patchwork.kernel.org/patch/9637821/

and maybe also this one:

https://patchwork.kernel.org/patch/9640261/

to see if it improves things for the intel_pstate "powersave" on that machine.

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[Bug 194963] schedutil governor causes audio problem in game

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--- Comment #4 from John (john.ettedgui@gmail.com) ---
(In reply to Viresh Kumar from comment #2)
> John,
> 
> Can you please give us the value of 
> /sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us
> 
> ?
> 
> Try making this around 10000 (10ms). This is how frequently we try to change
> the frequency and lowering it will make us more aggressive.

Hello Viresh,

cat /sys/devices/system/cpu/cpufreq/schedutil/rate_limit_us
10000

It's already at that value, are there others you'd like me to try?

(In reply to Rafael J. Wysocki from comment #3)
> It also would be good to test this patch:
> 
> https://patchwork.kernel.org/patch/9637821/
> 
> and maybe also this one:
> 
> https://patchwork.kernel.org/patch/9640261/
> 
> to see if it improves things for the intel_pstate "powersave" on that
> machine.

Hello Rafael,

I will try these and report.
Does it matter if I use both patches together?


Thank you!

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[Bug 194963] schedutil governor causes audio problem in game

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--- Comment #5 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
No, you can apply them both at the same time.

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[Bug 194963] schedutil governor causes audio problem in game

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--- Comment #6 from John (john.ettedgui@gmail.com) ---
The schedutil patch didn't seem to change anything, though the 4th hunk of
cpufreq_schedutil.c didn't apply and I had to do it manually, so it is possible
I messed up somewhere (I copied/pasted it so it's unlikely, but I thought it'd
be better to say it).

As for pstate, I think that's the first time I've seen my CPU scaling on
pstate's powersave. I've tried the game, and I think, but not sure, that when
it started the sound cracked for just a bit, maybe before the CPU scaled up
enough? After that no issue, and I verified the CPU was at its maximum
frequency. When I quit the game, the CPU scaled down to its minimum frequency
within 2 seconds. Pstate's performance still doesn't scale, is it expected? I
thought on pstate both would.

Thank you!

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[Bug 194963] schedutil governor causes audio problem in game

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |ASSIGNED

--- Comment #7 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
(In reply to John from comment #6)
> The schedutil patch didn't seem to change anything, though the 4th hunk of
> cpufreq_schedutil.c didn't apply and I had to do it manually, so it is
> possible I messed up somewhere (I copied/pasted it so it's unlikely, but I
> thought it'd be better to say it).

OK, this means that schedutil is not a good match for you.

It is a bit less aggressive than ondemand, on purpose.

There is one more schedutil change that you may try, but I need to prepare a
patch for that first.

> As for pstate, I think that's the first time I've seen my CPU scaling on
> pstate's powersave. I've tried the game, and I think, but not sure, that
> when it started the sound cracked for just a bit, maybe before the CPU
> scaled up enough?

Yes, that's possible.

> After that no issue, and I verified the CPU was at its
> maximum frequency. When I quit the game, the CPU scaled down to its minimum
> frequency within 2 seconds. Pstate's performance still doesn't scale, is it
> expected? I thought on pstate both would.

If you mean scaling_governor=performance, then it will always request the max
P-state now, as that's what it is supposed to be doing.

Thanks for the testing, the intel_pstate change will be queued up for 4.12 in
the next couple of days.

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--- Comment #8 from John (john.ettedgui@gmail.com) ---
(In reply to Rafael J. Wysocki from comment #7)
> OK, this means that schedutil is not a good match for you.
> 
> It is a bit less aggressive than ondemand, on purpose.

Oh I see, I didn't realize that, I thought it was about as dynamic as ondemand.
Then I am sorry about a wrong report!

> There is one more schedutil change that you may try, but I need to prepare a
> patch for that first.
> 

I'll be happy to test it whenever it's ready. Since I have plenty of workaround
there's of course no sense of urgence on my end.

> If you mean scaling_governor=performance, then it will always request the
> max P-state now, as that's what it is supposed to be doing.

Yes that is what I meant, I thought scaling_governor=performance with
driver=intel_pstate would scale unlike with driver=cpufreq, I was wrong again.

> Thanks for the testing, the intel_pstate change will be queued up for 4.12
> in the next couple of days.

Well thank you for this patch, I am happy to finally be able to use pstate :)


If you don't mind me asking here, since we talked about many different
governors, and their drivers, which one do you recommend for a desktop, that
does run games, but also other things that don't require much power. Based on
my tests I'm thinking either cpufreq's ondemand or pstate's powersave.

Thank you!

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[Bug 194963] schedutil governor causes audio problem in game

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEEDINFO

--- Comment #9 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
I would use intel_pstate "powersave" (with the patch you have tested applied).

One more question, though.

I guess that you used "schedutil" with acpi-cpufreq as a scaling_driver?

If that's correct, can you please also try to run intel_pstate in the passive
mode (that is, pass "intel_pstate=passive" to the kernel command line) and use
"schedutil" with that (scaling_driver will show "intel_cpufreq" in that
configuration)?

With acpi-cpufreq "schedutil" may under-provision things due to the way in
which turbo P-states are represented in the ACPI tables.

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--- Comment #10 from John (john.ettedgui@gmail.com) ---
(In reply to Rafael J. Wysocki from comment #9)
> I would use intel_pstate "powersave" (with the patch you have tested
> applied).
> 
Alright.
> One more question, though.
> 
> I guess that you used "schedutil" with acpi-cpufreq as a scaling_driver?
> 
Correct.
> If that's correct, can you please also try to run intel_pstate in the
> passive mode (that is, pass "intel_pstate=passive" to the kernel command
> line) and use "schedutil" with that (scaling_driver will show
> "intel_cpufreq" in that configuration)?
> 
> With acpi-cpufreq "schedutil" may under-provision things due to the way in
> which turbo P-states are represented in the ACPI tables.

I just tested it, and still had the audio cracking. I'm not convinced it was
any different from using it with acpi-cpufreq, but since I don't measure the
time between audio distortions I could be wrong.

Thank you!

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[Bug 194963] schedutil governor causes audio problem in game

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Len Brown (lenb@kernel.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lenb@kernel.org
           Hardware|x86-64                      |Intel

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Len Brown (lenb@kernel.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|Intel                       |All

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--- Comment #11 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
Created attachment 255621
  --> https://bugzilla.kernel.org/attachment.cgi?id=255621&action=edit
cpufreq: schedutil: Ramp down frequencies slower

One more patch for the schedutil governor to test.

It should make it ramp up frequency faster, so maybe it will help. :-)

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--- Comment #12 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
I forgot to say that the patch in comment #11 is based on the current
linux-next branch of the linux-pm.git repository:

https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/log/?h=linux-next

and it should be safe to test it along with that branch.

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--- Comment #13 from John (john.ettedgui@gmail.com) ---
I've tested it quickly and it seems to work just fine.
I've re-used my 4.10 kconfig file, and defaulted every new other option.

I'll keep running it and we'll see.

Is it ok that I didn't test the repository without the extra patch?

Thank you!

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--- Comment #14 from John (john.ettedgui@gmail.com) ---
Well actually it's not good enough for me yet, I still get the audio issue,
very rarely though. I'll switch to ondemand on the same kernel and see if I
also get it (since it's a different kernel who knows...).

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--- Comment #15 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
Just to be sure that nothing escapes us, can you please test the patch on top
of the linux-next branch *and* with intel_pstate in the passive mode
(intel_pstate=passive) instead of acpi-cpufreq?

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--- Comment #16 from John (john.ettedgui@gmail.com) ---
Well I've had the same issue on ondemand, then I switched to performance to see
and it was all fine, I switched back again to schedutil and since then it's
been fine. So maybe it was a heavy service running in the background at that
time or something like that...

Based on that, I will retract comment 14.

I will test it with intel_pstate=passive and report.

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--- Comment #17 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
Cool, thanks!

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--- Comment #18 from John (john.ettedgui@gmail.com) ---
So I've been on passive for about a day, and I didn't notice any difference
with acpi-cpufreq. As you've correctly stated in your email, I am not doing any
measurements so it's all a bit of a guesswork. I could plot frequencies if
needed.

One thing I forgot to mention earlier is that I use the most cpu intensive
resample method in pulseaudio (speex-float-10).

On another forum, one user tried to replicate my tests and never had any issue
or worse performance with standard schedutil from 4.10 on a 2500k.  I don't
know if he's using pulse or straight alsa, and if the former which resampler is
used. I'll try to get this information. Not sure what that means, but I thought
I might as well share this.

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |RESOLVED
         Resolution|---                         |PATCH_ALREADY_AVAILABLE

--- Comment #19 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
What it practically means is that the problem reported by you may be hard to
reproduce. :-)

Anyway, my conclusion is that the patch from comment #11 (or alternatively
https://patchwork.kernel.org/patch/9655173/) helps, so let me resolve this
report accordingly.

Whether or not the patch is accepted upstream, I'm not sure at this point,
because it may lead to increased energy consumption on other systems in
principle.

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--- Comment #20 from John (john.ettedgui@gmail.com) ---
Sure that's fine.

Assuming the patch will be accepted, what governor would you now suggest me to
use on what will be 4.12?

Thank you very much for your super quick help on this!

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--- Comment #21 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
(In reply to John from comment #20)
> Sure that's fine.
> 
> Assuming the patch will be accepted, what governor would you now suggest me
> to use on what will be 4.12?

If it is accepted, there won't be much difference between schedutil and the new
"powersave" algorithm in intel_pstate, so whichever of the two you prefer I
suppose. :-)

> Thank you very much for your super quick help on this!

No problem.

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--- Comment #22 from John (john.ettedgui@gmail.com) ---
I've just seen the patch has been checked in, so thank you :)

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