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

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Message-ID: <20140820141545.GA3242@krava.brq.redhat.com>
Date:	Wed, 20 Aug 2014 16:15:45 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>, ak@...ux.intel.com,
	peterz@...radead.org, eranian@...gle.com, dev@...yps.com,
	Michael Ellerman <michaele@....ibm.com>,
	Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: 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 <dev@...yps.com>
> 
> 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
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