On Tue, 16 Dec 2025 12:50:01 GMT, Paul Hübner <[email protected]> wrote:
>> The following function in `InstanceKlass` is supposed to return size in
>> words:
>>
>> static int size(int vtable_length, int itable_length,
>> int nonstatic_oop_map_size,
>> bool is_interface,
>> bool is_inline_type) {
>> return align_metadata_size(header_size() +
>> vtable_length +
>> itable_length +
>> nonstatic_oop_map_size +
>> (is_interface ? (int)sizeof(Klass*)/wordSize : 0) +
>> (is_inline_type ? (int)sizeof(InlineKlassFixedBlock) : 0));
>> }
>>
>> but `sizeof(InlineKlassFixedBlock)` returns a size in bytes. This adds 640
>> bytes instead of 80 bytes to all InlineKlasses.
>>
>> This can be seen by running `jcmd <pid> VM.classes` to check the size of the
>> InlineKlass of Integer before and after the fix for this:
>>
>> Before:
>>
>> 0x00000ffc0024d260 167 fully_initialized WS java.lang.Integer
>>
>> After:
>>
>> 0x000001800024d260 97 fully_initialized WS java.lang.Integer
>>
>>
>> That is in words. So this bug added an extra `(167 - 97) * 8 == 560` bytes.
>>
>> I've so far only done some local smoke testing with TEST=hotspot_valhalla
>
> src/hotspot/share/oops/instanceKlass.hpp line 1050:
>
>> 1048: nonstatic_oop_map_size +
>> 1049: (is_interface ? (int)sizeof(Klass*) / wordSize : 0) +
>> 1050: (is_inline_type ? (int)sizeof(InlineKlassFixedBlock) /
>> wordSize : 0));
>
> Do we have an `x / wordSize` helper function anywhere? Too much inline
> arithmetic makes it hard to maintain, imo.
I couldn't find. And there's a very large number of these in the code base. I
think this would be a cleanup that one would do outside of the Valhalla project.
-------------
PR Review Comment:
https://git.openjdk.org/valhalla/pull/1804#discussion_r2623513456
