[aarch64-port-dev ] RFR: 8135018: AARCH64: Missing memory barriers for CMS collector

[Andrew Haley]

On 09/08/2015 12:28 PM, Thomas Schatzl wrote:
> One minor change that may decrease overhead is to make these barriers
> conditional on CMSPrecleaningEnabled - but then I do not know how much
> impact that would have. The only web page I ever saw recommending to
> disable precleaning is some workaround for some bug...

Okay.  I've changed the patch to test CMSPrecleaningEnabled in
c1_LIRGenerator.cpp (which is shared code) and in
macroAssembler_aarch64.cpp.

In the case of gen_write_ref_array_post_barrier I left it as it was.
This code always writes the card table regardless of UseCondCardMark,
and I was slightly concerned that we would be racing with other
mutator threads.  (I now believe this reasoning is really nonsense
because all we're doing is racing to write zero, but I'm sure it
doesn't hurt and I feel more comfortable leaving it this way.)

> Not sure if you need a sponsor, but if so, I could do that.

Yes, please.  I need someone who will push it through jprt.

http://cr.openjdk.java.net/~aph/8135018-2/

Thanks,
Andrew.