On Mon, 20 Jan 2025 16:20:20 GMT, Matthias Ernst <d...@openjdk.org> wrote:
>> Certain signatures for foreign function calls (e.g. HVA return by value) >> require allocation of an intermediate buffer to adapt the FFM's to the >> native stub's calling convention. In the current implementation, this buffer >> is malloced and freed on every FFM invocation, a non-negligible overhead. >> >> Sample stack trace: >> >> java.lang.Thread.State: RUNNABLE >> at jdk.internal.misc.Unsafe.allocateMemory0(java.base@25-ea/Native >> Method) >> ... >> at >> jdk.internal.foreign.abi.SharedUtils.newBoundedArena(java.base@25-ea/SharedUtils.java:386) >> at >> jdk.internal.foreign.abi.DowncallStub/0x000001f001084c00.invoke(java.base@25-ea/Unknown >> Source) >> ... >> at >> java.lang.invoke.Invokers$Holder.invokeExact_MT(java.base@25-ea/Invokers$Holder) >> >> >> To alleviate this, this PR remembers and reuses up to two small intermediate >> buffers per carrier-thread in subsequent calls. >> >> Performance (MBA M3): >> >> >> master@764d70b7df18e288582e616c62b0d7078f1ff3aa >> Benchmark Mode Cnt Score Error Units >> PointsAlloc.circle_by_ptr avgt 30 9.197 ? 0.037 ns/op >> PointsAlloc.circle_by_value avgt 30 42.195 ? 0.088 ns/op <= >> ####### >> PointsAlloc.jni_ByteBuffer_alloc avgt 30 226.127 ? 35.378 ns/op >> PointsAlloc.jni_long_alloc avgt 30 25.297 ? 2.457 ns/op >> PointsAlloc.panama_alloc avgt 30 27.053 ? 1.915 ns/op >> >> After: >> Benchmark Mode Cnt Score Error Units >> PointsAlloc.circle_by_ptr avgt 30 9.156 ? 0.021 ns/op >> PointsAlloc.circle_by_value avgt 30 11.995 ? 0.051 ns/op <= >> ####### >> PointsAlloc.jni_ByteBuffer_alloc avgt 30 211.161 ? 23.284 ns/op >> PointsAlloc.jni_long_alloc avgt 30 24.885 ? 2.461 ns/op >> PointsAlloc.panama_alloc avgt 30 26.905 ? 1.935 ns/op >> >> >> `-prof gc` also shows that the new call path is fully scalar-replaced vs 160 >> byte/call before. > > Matthias Ernst has updated the pull request incrementally with three > additional commits since the last revision: > > - shift api boundary > - move bench > - revert formatting src/java.base/share/classes/jdk/internal/foreign/abi/CallBufferCache.java line 41: > 39: // Storing addresses, not MemorySegments turns out to be slightly > faster (write barrier?). > 40: private long address1; > 41: private long address2; Can we store just `MemorySegment`s here? It would avoid having to call `ofAddress` in `acquireOrAllocate`, and would slightly reduce the footprint when using compressed oops. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/23142#discussion_r1922704992
