RFR(M): 8008287: Code cache statistic variables for event tracing needs atomicity

[Nils Eliasson]

Hi,

I have fixed some atomicity issues for the sweeper tracing and did some 
refactoring at the same time, removing duplicate counters.

I guess people might have opinions on this, but I have chosen to only 
use the perf_counters when available instead of  always having a normal 
counter and an additional perf_counter in specific scenarios.

Also changed the type of the traversal counter (and the stack_traversal 
marker in nmethod). It should be good for 126 years of sweeping once a 
second anyway (and we don't complete full sweeps that often.)

http://bugs.sun.com/view_bug.do?bug_id=8008287
https://jbs.oracle.com/bugs/browse/JDK-8008287
http://cr.openjdk.java.net/~neliasso/8008287/webrev.04 
<http://cr.openjdk.java.net/%7Eneliasso/8008287/webrev.04>

Thanks,
Nils Eliasson