[aarch64-port-dev ] RFR (XS) 8252096: Shenandoah: adjust SerialPageShiftCount for x86_32 and JFR

[Aleksey Shipilev]

On 8/27/20 7:38 AM, Andrew Hughes wrote:
> How did you find the correct value? I've been considering backporting
> https://bugs.openjdk.java.net/browse/JDK-8152358 as it makes the assert
> print the expected value.

I printed out sizeof(JavaThread) in multiple build configurations, and discovered that with both JFR 
and Shenandoah it trips over 1024. Which means the expected count is log2_intptr(sizeof(class 
JavaThread)) - log2_intptr(64) = log2(2^10) - log2(2^6) = 4. That is basically +1 to current value.

> Anyway, if it only applies when Shenandoah + JFR are in operation, it explains
> why Azul have not seen it on upstream 8u. Change looks good to me and it will
> be good to get this fixed and JFR enabled on our x86 builds.

Yes.

-- 
Thanks,
-Aleksey