Messages in this thread | | | Date | Wed, 18 May 2016 19:38:33 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2 08/32] perf/x86/intel/cqm: add pmu sysfs attribute |
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On Wed, 11 May 2016, David Carrillo-Cisneros wrote:
> Expose max_recycle_threshold pmu attribute to user-space. > > Reviewed-by: Stephane Eranian <eranian@google.com> > Signed-off-by: David Carrillo-Cisneros <davidcc@google.com> > --- > arch/x86/events/intel/cqm.c | 48 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 48 insertions(+) > > diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c > index 54f219f..225b0c8 100644 > --- a/arch/x86/events/intel/cqm.c > +++ b/arch/x86/events/intel/cqm.c > @@ -393,9 +393,57 @@ static struct attribute_group intel_cqm_format_group = { > .attrs = intel_cqm_formats_attr, > }; > > +static ssize_t > +max_recycle_threshold_show( > + struct device *dev, struct device_attribute *attr, char *page) > +{ > + ssize_t rv; > + > + monr_hrchy_acquire_mutexes(); > + rv = snprintf(page, PAGE_SIZE - 1, "%u\n", > + __intel_cqm_max_threshold); > + monr_hrchy_release_mutexes();
So we acquire a gazillion of mutexes to read a single variable?
> + > + return rv; > +} > + > +static ssize_t > +max_recycle_threshold_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + unsigned int bytes; > + int ret; > + > + ret = kstrtouint(buf, 0, &bytes);
That number is not limited by any means. So 0 ... UINT_MAX is valid, correct?
> + if (ret) > + return ret; > + > + /* Mutex waits for rotation logic in all packages to complete. */
What's wrong with just setting the variable and let it take effect on the next rotation? That locking here is just pointless. It does not protect anything.
> + monr_hrchy_acquire_mutexes(); > + > + __intel_cqm_max_threshold = bytes; > + > + monr_hrchy_release_mutexes();
Thanks,
tglx
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