Tom Harwood wrote:
> Hi all,
> I'm trying to profile TLB misses, specifically, but my Beagleboard (with Siarhei Siamashka's watchdog patch) records zero samples on any event I've tried other than the default CPU_CYCLES. I have not exhaustively tried all event types yet, but a number of them, e.g. INSTR_EXECUTED, DCACHE_ACCESS.
Sorry, no ideas. Hopefully some folks on the list who speak "ARM" can help.
> There is one interesting metric in the log file, "backtraces skipped," below. I think that's due to JIT'd code running in the application, but it does suggest that oprofile is active.
The bt_lost_no_mapping stat should only come into play when you are doing callgraph profiling AND the oprofile kernel code fails to log a backtrace sample (implying that it can't find a mapping for the instruction address it was trying to record). when you're doing callgraph profiling, you get all the "normal" samples, plus backtraces recorded for each of those. The "normal" samples are the non-backtrace samples, which in your case is zero. Since you're not getting any normal samples, you certainly should not see any backtrace records recorded for them, and therefore, should not ever be seeing any backtraces skipped counts. The fact that you are is a bug -- which I reported to the oprofile kernel driver maintainer on May 27, 2009. This is fixed upstream now, but evidently not in your running kernel. But this is just a nit and you can ignore it.
> Any help would be much appreciated, thanks in advance!
> -- OProfile Statistics --
> Nr. sample dumps: 2
> Nr. non-backtrace samples: 0
> Nr. kernel samples: 0
> Nr. lost samples (no kernel/user): 0
> Nr. lost kernel samples: 0
> Nr. incomplete code structs: 0
> Nr. samples lost due to sample file open failure: 0
> Nr. samples lost due to no permanent mapping: 0
> Nr. event lost due to buffer overflow: 0
> Nr. samples lost due to no mapping: 0
> Nr. backtraces skipped due to no file mapping: 61787
> Nr. samples lost due to no mm: 0
> ---- Statistics for cpu : 0
> Nr. samples lost cpu buffer overflow: 0
> Nr. samples received: 0
> Nr. backtrace aborted: 0
> Nr. samples lost invalid pc: 0
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