Powertop suggests CONFIG_PM_ADVANCED_DEBUG kernel option

I am running Ubuntu 10.10 and I am also getting the same message in powertop.

How does one enable CONFIG_PM_ADVANCED_DEBUG?

This is not a bug, but qualifies as a question.
Suggest filing under the appropriate category.

Not that I am suggesting a 'ready to use' solution, just my findings for more understanding ....
I can enable the option, but am not sure whether the recompiled kernel will suit my machine well ...

I see this on line no. 3275 in <linux-source-2.6.35>/debian.master/config/config.common.ubuntu
 # CONFIG_PM_ADVANCED_DEBUG is not set

and is used in <linux-source-2.6.35>/drivers/base/power/sysfs.c as
#ifdef CONFIG_PM_ADVANCED_DEBUG
#ifdef CONFIG_PM_RUNTIME

static ssize_t rtpm_usagecount_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
 return sprintf(buf, "%d\n", atomic_read(&dev->power.usage_count));
}

static ssize_t rtpm_children_show(struct device *dev,
      struct device_attribute *attr, char *buf)
{
 return sprintf(buf, "%d\n", dev->power.ignore_children ?
  0 : atomic_read(&dev->power.child_count));
}

static ssize_t rtpm_enabled_show(struct device *dev,
     struct device_attribute *attr, char *buf)
{
 if ((dev->power.disable_depth) && (dev->power.runtime_auto == false))
  return sprintf(buf, "disabled & forbidden\n");
 else if (dev->power.disable_depth)
  return sprintf(buf, "disabled\n");
 else if (dev->power.runtime_auto == false)
  return sprintf(buf, "forbidden\n");
 return sprintf(buf, "enabled\n");
}

static DEVICE_ATTR(runtime_usage, 0444, rtpm_usagecount_show, NULL);
static DEVICE_ATTR(runtime_active_kids, 0444, rtpm_children_show, NULL);
static DEVICE_ATTR(runtime_enabled, 0444, rtpm_enabled_show, NULL);

#endif

In order to enable CONFIG_PM_ADVANCED_DEBUG we would also need to enable CONFIG_PM_DEBUG.

So still the questions remain: 1. how do I enable it? and 2. is it safe?
Thanks. I am not an advanced user, so I don't know much about kernels...

If you want to recompile, you can follow the kernel compilation guide on the wiki, and just before you compile, set CONFIG_PM_DEBUG and CONFIG_PM_ADVANCED_DEBUG to 'y' in config.common.ubuntu. I did this for a while and it was safe, but I got tired of recompiling with every kernel release.

That said, I would be pleased if these options were added to the default config that official kernels are compiled with, it doesn't really slow things down and makes powertop a lot more useful.

@Leif -- you say "doesn't really slow things down" can you quantify the slow down we will see?

As we are unable to easily quantify the overall cost of enabling this, and now are very close to release (for Natty) we are not going to be changing this there. We should review this early in Oneiric.

Thanks! Good luck with this.

Have added an Oneiric task, and set the importance so it it gets considered as part of planning, and add milestone if appropiriate.

Actually, CONFIG_PM_DEBUG is already set for i386/amd64 in Natty. Enabling CONFIG_PM_ADVANCED_DEBUG merely turns on some sysfs functions that have no runtime impact until accessed. I'm gonna enable this for Oneiric.

So you are saying that Natty should have this enabled? If I launch powertop it will not suggest enabling this setting?

Dhaval - Natty only has CONFIG_PM_DEBUG enabled. I watched powertop for awhile and didn't see any complaints about needing CONFIG_PM_ADVANCED_DEBUG.

> Enabling CONFIG_PM_ADVANCED_DEBUG merely turns on some sysfs
> functions that have no runtime impact until accessed. I'm gonna
> enable this for Oneiric.

No runtime impact.

Can we get CONFIG_PM_ADVANCED_DEBUG added to the Maverick (as current release) and/or Natty (as upcoming release) then? It'll be some time until we're able to roll Oneiric out to our users.

AfC

As a user, I would have to say that I would love it if you can get it into the current release.

Thanks for the effort! Much appreciated. Trying to squeeze every bit of battery life out of this x301.

Yes, if it doesn't hurt, please put this in one of the next Maverick Kernels.