Re: [PATCH v2 00/14] Add support for parameterized events from sysfs

On Fri, Aug 15, 2014 at 12:26:09AM -0700, Sukadev Bhattiprolu wrote:

From: Cody P Schafer <redacted>

What this patchset does:

 - the first patch (override sysfs in tools/perf via SYSFS_PATH) was sent out
   previously, but needed a resend anyhow. Having it is useful for testing the
   later changes to tools/perf.
 - the second patch is a bugfix to the powerpc hv-24x7 code which was
   previously sent out, which is a good idea to have when testing these patches
   on POWER8 hardware.

 - document perf sysfs and the changes to add parameterized events
   - semi-notably: removes the growing list of specific POWER cpu events and
     begins documenting them generically, much like the docs for
     /sys/modules/MODULENAME do for modules.
 - tools/perf changes to support parameterized events
 - export some parameterized events from the powerpc pmus hv_24x7 and hv_gpci

Description of "event parameters" from the documentation patch:

    Event parameters are a basic way for partial events to be specified in
    sysfs with per-event names given to the fields that need to be filled in
    when using a particular event.

    It is intended for supporting cases where the single 'cpu' parameter is
    insufficient. For example, POWER 8 has events for physical
    sockets/cores/cpus that are accessible from with virtual machines. To
    keep using the single 'cpu' parameter we'd need to perform a mapping
    between Linux's cpus and the physical machine's cpus (in this case
    Linux is running under a hypervisor). This isn't possible because
    bindings between our cpus and physical cpus may not be fixed, and we
    probably won't have a "cpu" on each physical cpu.

Description of the sysfs contents when events are parameterized (copied from an
included patch):

	Examples:

		domain=0x1,offset=0x8,starting_index=phys_cpu

	In the case of the last example, a value replacing "phys_cpu"
	would need to be provided by the user selecting the particular
	event. This is refered to as "event parameterization". All
	non-numerical values indicate an event parameter.

Notes on how perf-list displays parameterized events (and how to use them,
again culled from an included patch):

	PARAMETERIZED EVENTS
	--------------------

	Some pmu events listed by 'perf-list' will be displayed with '?' in
	them. For example:

	  hv_gpci/dtbp_ptitc,phys_processor_idx=?/

	This means that when provided as an event, a value for
	phys_processor_idx must also be supplied. For example:

	  perf stat -e 'hv_gpci/dtbp_ptitc,phys_processor_idx=0x2/' ...

hi,
is the reason for this to document this field for event
in "events/<event>" file?

Because once you have the field (phys_processor_idx) defined in
"formats/phys_processor_idx" you should be able to use it as in
your example:

   perf stat -e 'hv_gpci/dtbp_ptitc,phys_processor_idx=0x2/'

without any changes

thanks,
jirka