Messages in this thread | | | Subject | Re: [PATCH 1/2] perf-events: Add support for supplementary event registers v2 | From | Peter Zijlstra <> | Date | Fri, 12 Nov 2010 18:33:12 +0100 |
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On Fri, 2010-11-12 at 18:17 +0100, Stephane Eranian wrote: > I looked at this patch thinking how could this be reused for LBR_SELECT. > > I am wondering if storing the extra MSR value in attr.config is really the way > to go now as opposed to adding/overloading a field. > > For OFFCORE_RESPONSE, it makes sense to use attr.config because this is > a refinement of the event (a sub-sub event if you want).
Correct, it makes sense for offcore and load-latency, not so much for lbr_config.
> For LBR_SELECT, you also need to pass a value, but there is no specific event > associated with it. You can enable LBR with any event you want. Thus, > storing the > LBR_SELECT value independently would also make sense. And if we have this > field for LBR_SELECT then we may as well use it for OFFCORE_REPONSE.
That would assume a single event doesn't contain offcore and lbr, no? Currently the extra_reg thing assumes there's only one extra reg encoded in the config word.
> The alternative would be to consider LBR_SELECT also as a refinement of > the event being measured. Though by itself, it wouldn't do anything, it would > have to be combine with a PERF_SAMPLE_BRANCH_STACK to attr.sample_type.
A separate field for the lbr_config seems to make most sense, we could of course use the top 16 bits for lbr, the next 16 for offcore/ll and the bottom 32 for eventsel, but that's mighty crowded.
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