Re: [PATCH 0/26] oprofile: Performance counter multiplexing

From: Robert Richter
Date: Fri Mar 05 2010 - 11:46:37 EST

On 26.02.10 15:51:04, Andi Kleen wrote:
> That said the biggest problem with oprofile right now that the
> new buffer it's using is quite a lot less reliable and drops
> events left and right on any non trivial load. That makes
> oprofile very unreliable, especially in call graph mode.

(cc'ing Steve)


the tests I run with oprofile do not indicate unreliable ring_buffer
behavior. Maybe my use cases and loads are different. Can you describe
a setup where this may happen for sure? What is the impact, do you
have lost samples or inconsistent buffer data? Is the data loss in
kernel or user space? Also, I am not aware that the ring_buffer is
unreliable for ftrace or tracepoints, where it is heavily used. I
really want to find the root cause here.



Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@xxxxxxx

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