perfasm and the <kernel> region

[Aleksey Shipilev]

On 04/23/2015 04:07 PM, Aleksey Shipilev wrote:
> On 04/23/2015 03:39 PM, Chris Vest wrote:
>> I’m assuming the time spent in the system calls for the IO and the
>> blocking/unblocking of threads are both included in the <kernel>
>> region. Would it be possible to break them out? I tried strace’ing
>> the benchmark, but the overhead of strace is so big that it changes
>> the behavioural patterns of the code, ruining the measurement.
> 
> "perfasm" processes whatever events perf is providing back to us. At
> this point, we attribute all events from the negative addresses as the
> <kernel> region. One can massage perfasm code to parse those properly as
> well, like this:

Okay, that's a good improvement on my machines, so I pushed:
  https://bugs.openjdk.java.net/browse/CODETOOLS-7901405

The comment in the bug explains what sys options might need to be
enabled for kernel symbols to be resolveable.

Thanks,
-Aleksey