Hi Rafael, Mark,

On Sun, Feb 5, 2012 at 12:04 PM, Rafael J. Wysocki [off-list ref] wrote:

On Sunday, February 05, 2012, mark gross wrote:

quoted

On Fri, Feb 03, 2012 at 03:04:43PM +0100, Pihet-XID, Jean wrote:

quoted

Looping in linux-pm

On Fri, Feb 3, 2012 at 1:14 AM, Venkatesh Pallipadi [off-list ref] wrote:

quoted

Looks like change "PM QoS: Move and rename the implementation files"
made pm_qos depend on CONFIG_PM which depends on
PM_SLEEP || PM_RUNTIME

That breaks CPU C-states with kernels not having these CONFIGs, causing CPUs
to spend time in Polling loop idle instead of going into deep C-states,
consuming way way more power. This is with either acpi idle or intel idle
enabled.

Either CONFIG_PM should be enabled with any pm_qos users or
the !CONFIG_PM pm_qos_request() should return sane defaults not to break
the existing users. Here's is the patch for the latter option.

I think the real question is whether PM QoS should be functional in
all cases (as is ACPI) or whether only if certain options are set
(CONFIG_PM).
In the current code if CONFIG_PM is not enabled, a dummy PM QoS API is
provided as function stubs in order for the build to succeed.

Rafael, Mark,
What do you think? Should PM QoS be enabled in all cases? Are there
any known dependencies with CONFIG_PM?

Yes I do think pm_qos interfaces should be enabled all the time and be
independent of CONFIG_PM.  Also, I still am not a fan of the renaming
patch but, as the argument for and against renaming cannot be based on
quantifiable things I've chosen not to let it bother me.

I think Venki's change is a band aid and we should fix it right by not
having a dependency on config_pm for the interface to behave.

I'll take a look at why there is now a dependency before I have more to
say.

In kernel/power/Makefile:

obj-$(CONFIG_PM)                += main.o qos.o

I guess that explains things. :-)

Initially I thought we should have a way of disabling the feature on
some (minimal) kernels and so thought CONFIG_PM was the option to use.

It's quite easy to make qos.o be independent of CONFIG_PM, in which case the
code added by Venki can be removed, so patches welcome (for 3.4, though).

I am working on it, more to come soon.

Thanks,
Rafael

Thanks,
Jean

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