On Mon, 15 Apr 2024 03:24:07 GMT, Vladimir Kozlov <k...@openjdk.org> wrote:
>> This is part of changes which try to reduce size of `nmethod` and `codeblob`
>> data vs code in CodeCache.
>> These changes reduced size of `nmethod` header from 288 to 232 bytes. From
>> 304 to 248 in optimized VM:
>>
>> Statistics for 1282 bytecoded nmethods for C2:
>> total in heap = 5560352 (100%)
>> header = 389728 (7.009053%)
>>
>> vs
>>
>> Statistics for 1322 bytecoded nmethods for C2:
>> total in heap = 8307120 (100%)
>> header = 327856 (3.946687%)
>>
>>
>> Several unneeded fields in `nmethod` and `CodeBlob` were removed. Some
>> fields were changed from `int` to `int16_t` with added corresponding asserts
>> to make sure their values are fit into 16 bits.
>>
>> I did additional cleanup after recent `CompiledMethod` removal.
>>
>> Tested tier1-7,stress,xcomp and performance testing.
>
> Vladimir Kozlov has updated the pull request incrementally with one
> additional commit since the last revision:
>
> Union fields which usages do not overlap
src/hotspot/share/memory/heap.hpp line 58:
> 56: void set_length(size_t length) {
> 57: LP64_ONLY( assert(((length >> 32) == 0), "sanity"); )
> 58: _header._length = (uint32_t)length;
Suggestion:
_header._length = checked_cast<uint32_t>length;
src/hotspot/share/memory/heap.hpp line 63:
> 61: // Accessors
> 62: void* allocated_space() const { return (void*)(this +
> 1); }
> 63: size_t length() const { return
> (size_t)_header._length; }
This cast looks unnecessary.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18768#discussion_r1566784458
PR Review Comment: https://git.openjdk.org/jdk/pull/18768#discussion_r1566784587
