Messages in this thread | | | Date | Wed, 20 Feb 2013 22:48:16 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH] perf x86: Change SandyBridge and IvyBrige instructions event to be precise |
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> I don't think it buys you much. People read too much into what > PEBS gives you. I can show you examples where PEBS > is worse than no PEBS.
Nothing is perfect in sampling, but the precise instructions event is definitely better in a range of situations. It avoids a lot of shadow effects.
I think it's a good choice for a lot of situations, although on Ivy Bridge without EventingRip the BB walking is still fairly expensive.
It would be a good default for the "user only asks for instructions for sampling and nothing else" situation, especially on Haswell which has EventingRip. But that's not straight forward to detect.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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