Re: [PATCH] perf, x86: Add workaround for MEM_*_RETIRED errata BV98

[Andi Kleen]

> Unfortunately, Andi's patch fails to correct the problem though
> it is the right approach. As he said, the problem is unfortunately

perf stat -a / record -a / top will work.

The case it doesn't fix is per thread when the other sibling
is not running a counter.

Essentially with the patch you may still get under-counting
on these specific events if they run per thread (or are really
unlucky in multiplexing), but never over-counting on anything.

In the past Ingo's guidance was to focus on the most common 
use cases, which I think this patch does.

It would be possible to fix the per thread mode too, but it would
need quite a bit of new infrastructure and I have doubts that's 
worth it.

-Andi
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