Fwd: RR(S): 8009062 poor performance of JNI AttachCurrentThread after fix for 7017193

[Dmitry Samersoff]

Hi Everybody,

Here is webrev of changes I'm about to integrate:

http://cr.openjdk.java.net/~dsamersoff/8009062/webrev.13/

The problem:

Under Linux stack of main thread is growable, so we have to make sure
that address we plan to put a guard pages to and below is not mapped.

Historically we find bounds of the stack of main thread by seeking
/proc/self/maps for "[stack]" and parsing this line.

But after intensive testing we figured out that it's not required to
re-read stack bounds after create_attached_thread() because we are
manually grow stack up to the bounds in create_attached_thread()


Solution:

I use mincore(2) to check whether
the page is mapped or not. Typically mincore(2) is used to check whether
the page is resides in physical memory or not, but this function returns
-1 and set errno to ENOMEM if a region we are asking about contains not
mapped memory.

Testing:

Passed jprt, jck and and couple of ute tests. Wrote special regression test.

-Dmitry

-- 
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.