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

[Roman Kennke]

Looks ok to me.

Thanks,
Roman

Am Donnerstag, den 20.08.2020, 15:03 +0200 schrieb Aleksey Shipilev:
> Hi,
> 
> Once I added bootcycle-images to x86_32 test configurations, this
> failure was discovered:
> 
> #  Internal Error (/home/shade/trunks/shenandoah-
> jdk8/hotspot/src/share/vm/runtime/os.cpp:1280), 
> pid=490815, tid=0xf5fefb40
> #  assert(SerializePageShiftCount == count) failed: thread size
> changed, fix SerializePageShiftCount 
> constant
> 
> It happens when all three things hold true:
>    - JFR is enabled at build time
>    - Shenandoah is enabled at build time (i.e. the build config is
> not "minimal1")
>    - 32-bit VM is being built
> 
> Therefore, it only affects aarch64-port/jdk8u-shenandoah, and here is
> the minimal fix that adjusts 
> the constant when all three things are in effect at the same time:
> 
> diff -r ed70d5208f5f src/share/vm/utilities/globalDefinitions.hpp
> --- a/src/share/vm/utilities/globalDefinitions.hpp      Mon Jun 22
> 20:26:02 2020 +0800
> +++ b/src/share/vm/utilities/globalDefinitions.hpp      Thu Aug 20
> 13:03:44 2020 +0200
> @@ -143,12 +143,18 @@
>   // log2_intptr(sizeof(class JavaThread)) - log2_intptr(64);
>   // see os::set_memory_serialize_page()
>   #ifdef _LP64
>   const int SerializePageShiftCount = 4;
>   #else
> +#if INCLUDE_JFR && INCLUDE_ALL_GCS
> +// JavaThread already has quite a few Shenandoah fields. Adding many
> JFR fields
> +// trips sizeof(JavaThread) > 1024. Need to adjust it here.
> +const int SerializePageShiftCount = 4;
> +#else
>   const int SerializePageShiftCount = 3;
>   #endif
> +#endif
> 
>   // An opaque struct of heap-word width, so that HeapWord* can be a
> generic
>   // pointer into the heap.  We require that object sizes be measured
> in
>   // units of heap words, so that that
>   //   HeapWord* hw;
> 
> 
> Testing: Linux {x86_64, x86_32} x {zero, minimal1, server} x
> {default, jfr} bootcycle-images build
>