[aarch64-port-dev ] [URGENT] RFR (XS): Adjust code stub sizes for Shenandoah and future backports

[Aleksey Shipilev]

On 6/18/19 10:41 PM, Andrew John Hughes wrote:
> On 18/06/2019 20:27, Aleksey Shipilev wrote:
>> http://cr.openjdk.java.net/~shade/shenandoah/8u-codestub-sizes/webrev.01/
>>
>> This is the unnumbered fix, because it is specific to Shenandoah 8u. I prefer to fix it right in
>> integration forest to unblock testing. Current testing shows that Windows x86_64 fastdebug build
>> cannot start with -XX:+UseShenandoahGC, because code stubs are too small to fit Shenandoah code. It
>> is enough to fit the same code on Linux, though.
>>
>> So, we need to adjust it. Upstream code made multiple adjustments over the years, and I would prefer
>> not to second-guess that, and just pick up the values from current jdk/jdk:
>>   http://hg.openjdk.java.net/jdk/jdk/file/17f24c0e2f01/src/hotspot/cpu/x86/stubRoutines_x86.hpp#l34
>>
>> http://hg.openjdk.java.net/jdk/jdk/file/17f24c0e2f01/src/hotspot/cpu/aarch64/stubRoutines_aarch64.hpp#l42
>>
>> Testing: Shenandoah tests on {x86_64} x {Linux, Windows} x {release, fastdebug, slowdebug}
> 
> Can this not be made conditional on Shenandoah being enabled? I'm wary
> of us diverging from upstream here.

No, it is a compile-time constant, we cannot conditionalize it on runtime flag.

Bumping it up seems rather safe: it wastes a handful of kilobytes in buffers, but it is also tedious
to update every time. This is why I bumped it all the way up to current jdk/jdk limits.

-Aleksey