Messages in this thread | | | Date | Mon, 15 Jun 2009 20:28:28 +0200 | From | Ingo Molnar <> | Subject | Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods |
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* Ingo Molnar <mingo@elte.hu> wrote:
> The GUP based method is pretty generic though - and can be used on > other architectures as well. It's not as fast as direct access > though.
Another question is: your patch switches over all normal exceptions from IRET to hand-unroll+RET.
It would be really nice to benchmark it (via 'perf stat' for example ;-) whether that's a slowdown or a speedup.
If it's a slowdown then the decision is easy: we dont want this, we want to push the overhead into the sampling code, away from common codepaths.
[ If on the other hand it's a speedup of a few cycles then we have the problem of me suddenly liking this patch a whole lot more ;-) ]
Ingo
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