[8u] RFR: 8221355: Performance regression after JDK-8155635 backport into 8u

[Severin Gehwolf]

Hi,

Could I please get a review of this 8u212 performance regression fix?

webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8221355/01/webrev/
Bug: https://bugs.openjdk.java.net/browse/JDK-8221355

Before this fix:

$ time ./bin/java UnsafeGetObject 
1204 ms
1212 ms
1237 ms
1289 ms
1348 ms

real	0m6.354s
user	0m6.330s
sys	0m0.023s

After this fix:

$ time ./bin/java UnsafeGetObject 
54 ms
51 ms
43 ms
45 ms
44 ms

real	0m0.302s
user	0m0.303s
sys	0m0.009s

UnsafeGetObject.java is from:
https://bugs.openjdk.java.net/browse/JDK-8181822

Testing: Sanity testing with java.{,io,lang,math,net,nio,security,util} tests.

Thoughts?

Thanks,
Severin