Re: [PATCH 9/9] perf tool: Add pmu event alias support

Yan, Zheng
2012-05-04T12:33:05Z

On 05/04/2012 04:05 AM, Jiri Olsa wrote:
> On Thu, May 03, 2012 at 01:24:21PM +0200, Peter Zijlstra wrote:
>> On Thu, 2012-05-03 at 12:56 +0200, Jiri Olsa wrote:
>>> - in sysfs you would have directory with aliases (now called 'events')
>>> - each alias is sysfs dir, with file attrs:
>>> file name = term name, file value = term value
>>> eg.:
>>> events/
>>> CAS_COUNT_RD/
>>> # files:
>>> config - value 1
>>> config1 - value 2
>>> mask - value ...
>>
>> I'd prefer the thing Yan proposed (if the sysfs folks let us),
>>
>> $foo/events/QHL_REQUEST_REMOTE_READS
>>
>> with contents: "event=0x20,umask=0x4"
>>
>>> this way it's also possible to add extra terms to existing alias
>>> in command line if needed... might be handy
>>>
>> That should always be possible, if you modify the parser to take things
>> like:
>>
>> event=0x20,umask=0x4,event=0x21
>>
>> and have latter values override earlier values, so it collapses into:
>>
>> umask=0x4,event=0x21
>>
>> you can simply take whatever comes out of the event file and stick extra
>> bits at the end.
>
> I discussed this with Peter on irc, so I'll try to sum it up
>
> we have following options so far:
>
> with event alias 'al' with definition 'config=1,config1=1,config2=2'
>
> 1) inside parse_events_add_pmu function
> once alias term is detected as part of event definition 'pmu/al/mod' we
> construct new event 'pmu/config=1,config1=1,config2=2/mod' and rerun the
> event parser on that
>
> 2) inside parse_events_add_pmu function
> once alias term is detected as part of event definition 'pmu/al/mod' we
> replace that term with list of terms for that alias definition and run
> perf_pmu__config with this new term list
>
> 3) during bison/flex processing
> have option 2) embeded inside flex/bison rules. Once alias term
> is detected, insert the aliased terms directly to the list of terms,
> not replacing expos as in option 2.
>
>
> - option 1 is currently implemented
> - options 2 and 3 requires the aliased config is loaded/parsed from pmu
> sysfs tree in form of terms list
> - option 3 is a little fuzzy for me now on how to integrate this with
> flex/bison
>
> My interest here is to go with option 2 or 3 if possible - preferrably 2 ;),
> because I think it's better/cleaner to deal with terms in one place once they
> are parsed - in parse_events_add_pmu function.
>
> I think there's no need to re run the whole parser (option 1) when we
> have the whole thing ready by adding just extra terms.
>
> thoughts?
>

I agree with you, option 2 is cleaner than option 1. I will try implementing it

Thank you
Yan, Zheng