Subject: Re: [PATCH 2/3] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU

From: Gautham R Shenoy <[email-masked]>
Date: Wed, 4 Dec 2019 18:07:28 +0530

Hi Kamalesh,

On Tue, Dec 03, 2019 at 07:07:53PM +0530, Kamalesh Babulal wrote:
> On 11/27/19 5:31 PM, Gautham R. Shenoy wrote:
> > From: "Gautham R. Shenoy" <[email-masked]>
> > 
> > On Pseries LPARs, to calculate utilization, we need to know the
> > [S]PURR ticks when the CPUs were busy or idle.
> > 
> > The total PURR and SPURR ticks are already exposed via the per-cpu
> > sysfs files /sys/devices/system/cpu/cpuX/purr and
> > /sys/devices/system/cpu/cpuX/spurr.
> > 
> > This patch adds support for exposing the idle PURR and SPURR ticks via
> > /sys/devices/system/cpu/cpuX/idle_purr and
> > /sys/devices/system/cpu/cpuX/idle_spurr.
> 
> The patch looks good to me, with a minor file mode nit pick mentioned below.
> 
> > 
> > Signed-off-by: Gautham R. Shenoy <[email-masked]>
> > ---
> >  arch/powerpc/kernel/sysfs.c | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> > index 80a676d..42ade55 100644
> > --- a/arch/powerpc/kernel/sysfs.c
> > +++ b/arch/powerpc/kernel/sysfs.c
> > @@ -1044,6 +1044,36 @@ static ssize_t show_physical_id(struct device *dev,
> >  }
> >  static DEVICE_ATTR(physical_id, 0444, show_physical_id, NULL);
> > 
> > +static ssize_t idle_purr_show(struct device *dev,
> > +			      struct device_attribute *attr, char *buf)
> > +{
> > +	struct cpu *cpu = container_of(dev, struct cpu, dev);
> > +	unsigned int cpuid = cpu->dev.id;
> > +	struct lppaca *cpu_lppaca_ptr = paca_ptrs[cpuid]->lppaca_ptr;
> > +	u64 idle_purr_cycles = be64_to_cpu(cpu_lppaca_ptr->wait_state_cycles);
> > +
> > +	return sprintf(buf, "%llx\n", idle_purr_cycles);
> > +}
> > +static DEVICE_ATTR_RO(idle_purr);
> 
> per cpu purr/spurr sysfs file is created with file mode 0400. Using
> DEVICE_ATTR_RO for their idle_* variants will create sysfs files with 0444 as
> their file mode, you should probably use DEVICE_ATTR() with file mode 0400 to
> have consist permission for both variants.

Thanks for catching this. I missed checking the permissions of purr
and spurr. Will send another version.

> -- 
> Kamalesh