On Fri, 26 Apr 2024 21:16:03 GMT, Vladimir Kozlov <k...@openjdk.org> wrote:
> Move immutable nmethod's data from CodeCache to C heap. It includes
> `dependencies, nul_chk_table, handler_table, scopes_pcs, scopes_data,
> speculations, jvmci_data`. It amounts for about 30% (optimized VM) of space
> in CodeCache.
>
> Use HotSpot's `os::malloc()` to allocate memory in C heap for immutable
> nmethod's data. Bail out compilation if allocation failed.
>
> Shuffle fields order and change some fields size from 4 to 2 bytes to avoid
> nmethod's header size increase.
>
> Tested tier1-5, stress,xcomp
>
> Our performance testing does not show difference.
>
> Example of updated `-XX:+PrintNMethodStatistics` output is in JBS comment.
src/hotspot/share/code/nmethod.cpp line 1484:
> 1482: // Calculate positive offset as distance between the start of
> stubs section
> 1483: // (which is also the end of instructions section) and the start
> of the handler.
> 1484: CHECKED_CAST(_unwind_handler_offset, int16_t, (_stub_offset -
> code_offset() - offsets->value(CodeOffsets::UnwindHandler)));
Suggestion:
int unwind_handler_offset = code_offset() +
offsets->value(CodeOffsets::UnwindHandler);
CHECKED_CAST(_unwind_handler_offset, int16_t, _stub_offset -
unwind_handler_offset);
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18984#discussion_r1581644356
