On Wed, 30 Apr 2025 15:33:52 GMT, Per Minborg <[email protected]> wrote:
>> This PR is based on the work of @mernst-github and aims to implement an
>> _internal_ thread-local 'stack' allocator, which works like a dynamically
>> sized arena, but with reset functionality to reset the allocated size back
>> to a certain level. The underlying memory could stay around between calls,
>> which could improve performance.
>>
>> Re-allocated segments are not zeroed between allocations.
>
> Per Minborg has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Improve on comments
src/java.base/share/classes/jdk/internal/foreign/BufferStack.java line 185:
> 183: long size = layout.byteAlignment() > JAVA_LONG.byteSize()
> 184: ? Utils.alignUp(layout.byteSize(),
> layout.byteAlignment())
> 185: : layout.byteSize();
We already do this kind of conditional alignment in `SegmentFactories` (see the
use of `MAX_MALLOC_ALIGN`). I suggest re-using that logic, by passing the
alignment to `PerThread::of`, and then forwarding it to the `arena.allocate`
call. The other overload can pass `1` as the alignment.
test/jdk/java/foreign/TestBufferStack.java line 124:
> 122: outOfStack = hugeFrame.allocate(4);
> 123: assertEquals(hugeFrame.scope(), outOfStack.scope());
> 124:
> assertTrue(outOfStack.asOverlappingSlice(stackSegment).isEmpty());
Pre-existing but: I think `segment11` can be used here, and `stackSegment` is
not actually needed?
test/jdk/java/foreign/TestBufferStackStress.java line 44:
> 42: import static org.junit.jupiter.api.Assertions.*;
> 43:
> 44: public class TestBufferStackStress extends NativeTestHelper {
I don't think this test strictly needs to extend `NativeTestHelper`.
test/jdk/java/foreign/TestBufferStackStress2.java line 98:
> 96: System.gc();
> 97: }
> 98: segment.get(ValueLayout.JAVA_BYTE, i);
Won't this read out of bounds? `SMALL_ALLOC_SIZE` is only 8.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2068999305
PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2068978694
PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2069007343
PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2069198088
