Re: [PATCH v4 01/10] tools/perf: support parsing parameterized events

On Wed, Oct 01, 2014 at 11:06:27AM +0200, Jiri Olsa wrote:

On Thu, Sep 25, 2014 at 07:25:20PM -0700, Sukadev Bhattiprolu wrote:

quoted

Jiri Olsa [jolsa@redhat.com] wrote:
| On Wed, Sep 24, 2014 at 12:27:15PM -0700, Sukadev Bhattiprolu wrote:
| > From: Cody P Schafer [off-list ref]
| > 
| > Enable event specification like:
| > 
| > 	pmu/event_name,param1=0x1,param2=0x4/
| > 
| > Assuming that
| > 
| > 	/sys/bus/event_source/devices/pmu/events/event_name
| > 
| > Contains something like
| > 
| > 	param2=foo,bar=1,param1=baz
| 
| hum, so what happened to the '?' ... AFAIU from out last discussion,
| you wanted to mark terms which are mandatory and user must provide
| values for them.. and I thought the decision was to have following
| alias record:
| 
|   $ cat /sys/bus/event_source/devices/pmu/events/event_name
|   param2=?,bar=1,param1=?
| 
| while perf would scream if any of param1/2 wasnt filled like for:
|   pmu/event_name,param1=0x1/

Sorry, I meant to make perf list consistent with sysfs.

Consider these two sysfs entries:

	$ cat HPM_0THRD_NON_IDLE_CCYC__PHYS_CORE 
	domain=0x2,offset=0xe0,starting_index=core,lpar=0x0

	$ cat HPM_0THRD_NON_IDLE_CCYC__VCPU_HOME_CORE 
	domain=0x3,offset=0xe0,starting_index=vcpu,lpar=sibling_guest_id

In the first one, starting_index refers to a 'core' while in the second
it refers to a vcpu. This serves as a "hint" for the parameter's meaning.

By replacing both with 'starting_index=?' we lose that hint.

Should we fix both sysfs and 'perf list' to say

	starting_index=?core 

Peter, Ingo,
any opinions on this? Overall explanation is in here:
http://marc.info/?l=linux-kernel&m=141158688307356&w=2

Consistency is good, and you indeed need to indicate it is a parameter.
I'm not entirely sure about ?core, but I suppose its easy to parse and
clear enough to read.

So the typical optional argument syntax would be like $arg or <type>
like. But overall I have no objection as long as you keep the lot
consistent and parsable.