Re: [RFC PATCH 2/5] perf jevents: add support for arch recommended events

[John Garry]

On 08/12/2017 12:29, Jiri Olsa wrote:
> On Wed, Dec 06, 2017 at 03:20:14PM +0000, John Garry wrote:
> > On 06/12/2017 13:36, Jiri Olsa wrote:
> > > On Wed, Dec 06, 2017 at 12:13:16AM +0800, John Garry wrote:
> > > > For some architectures (like arm64), there are architecture-
> > > > defined recommended events. Vendors may not be obliged to
> > > > follow the recommendation and may implement their own pmu
> > > > event for a specific event code.
> > > >
> > > > This patch adds support for parsing events from arch-defined
> > > > recommended JSONs, and then fixing up vendor events when
> > > > they have implemented these events as recommended.
> > >
> > > in the previous patch you added the vendor support, so
> > > you have arch|vendor|platform key for the event list
> > > and perf have the most current/local event list
> > >
> > > why would you need to fix it? if there's new event list,
> > > the table gets updated, perf is rebuilt.. I'm clearly
> > > missing something ;-)
> >
> > The 2 patches are quite separate. In the first patch, I just added support
> > for the vendor subdirectory.
> >
> > So this patch is not related to rebuilding when adding a new event list or
> > dependency checking.
> >
> > Here we are trying to allow the vendor to just specify that an event is
> > supported as standard in their platform, without duplicating all the
> > standard event fields in their JSON. When processing the vendor JSONs, the
> > jevents tool can figure which events are standard and create the proper
> > event entries in the pmu events table, referencing the architecture JSON.

Hi jirka,

> I think we should keep this simple and mangle this with some pointer logic
>
> now you have arch/vendor/platform directory structure..

I'm glad that there seems to be no objection to this, as I feel that 
this was a problem.

why don't
> you add events for every such directory? I understand there will
> be duplications, but we already have them for other archs and it's
> not big deal:

The amount of duplication was the concern. As mentioned earlier, it 
would be anticipated that every vendor would implement these events as 
recommended, so a copy for every platform from every vendor. We're 
looking for a way to avoid this.

Actually having a scalable JSON standard format for pmu events, which 
allows us to define common events per architecture / vendor and 
reference them per platform JSON could be useful.

Here we're dealing with trade-off between duplication (simplicity) vs 
complexity (or over-engineering).

> 	[jolsa@krava perf]$ grep -r L2_RQSTS.DEMAND_DATA_RD_MISS pmu-events/arch/*
> 	pmu-events/arch/x86/broadwell/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/haswell/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/broadwellde/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/haswellx/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/skylake/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/skylakex/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
> 	pmu-events/arch/x86/broadwellx/cache.json:        "EventName": "L2_RQSTS.DEMAND_DATA_RD_MISS",
>
> thanks,
> jirka

Cheers,
John

> .