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

From: John Garry
Date: Fri Dec 08 2017 - 10:42:37 EST


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


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