On Fri, 17 Apr 2026 10:43:42 GMT, Tobias Hartmann <[email protected]> wrote:
> The test `compiler/print/CompileCommandMemLimit.java` fails because we > suddenly don't hit the expected memory limit anymore when compiling empty > method `TestMain::method2` with `--enable-preview`. In fact, the VM is > reporting that no memory is used for compilation at all: > > c1 (27) (ok) Arena usage > compiler/print/CompileCommandMemLimit$TestMain::method2(()V): Total Usage: 0 > > > I added some logging to the > `CompilationMemoryStatistic::on_arena_chunk_allocation` path in > `ChunkPool::allocate_chunk` and noticed that the only difference is that with > `--enable-preview` we don't have this allocation in > `Thread::current()->resource_area()`: > > V [libjvm.so+0x4bb99c] ChunkPool::allocate_chunk(Arena*, unsigned long, > AllocFailStrategy::AllocFailEnum)+0x16c > V [libjvm.so+0x4bc28d] Arena::grow(unsigned long, > AllocFailStrategy::AllocFailEnum)+0x5d > V [libjvm.so+0x7a4d83] > DebugInformationRecorder::DebugInformationRecorder(OopRecorder*)+0x43 > V [libjvm.so+0x58e3d1] Compilation::initialize()+0xb1 > V [libjvm.so+0x58fe1c] Compilation::compile_method()+0x6c > V [libjvm.so+0x590190] Compilation::Compilation(AbstractCompiler*, ciEnv*, > ciMethod*, int, BufferBlob*, bool, DirectiveSet*)+0x1f0 > V [libjvm.so+0x590866] Compiler::compile_method(ciEnv*, ciMethod*, int, > bool, DirectiveSet*)+0xb6 > > > The reason is that with `--enable-preview` -> `-XX:+UseFieldFlattening` we > have a new code path `ciInstanceKlass::compute_nonstatic_fields_impl` that > processes flat fields and creates `ciField` objects for those. We hit that > code path very early during `ciObjectFactory::init_shared_objects` for some > core-libs klass: > > > V [libjvm.so+0x4bb99c] ChunkPool::allocate_chunk(Arena*, unsigned long, > AllocFailStrategy::AllocFailEnum)+0x16c > V [libjvm.so+0x4bc28d] Arena::grow(unsigned long, > AllocFailStrategy::AllocFailEnum)+0x5d > V [libjvm.so+0x10bfdce] Symbol::as_C_string() const+0x1e > V [libjvm.so+0x69da5c] ciField::ciField(ciField*, ciField*)+0x7c > V [libjvm.so+0x6a6ab8] > ciInstanceKlass::compute_nonstatic_fields_impl(GrowableArray<ciField*> > const*, GrowableArray<ciField*> const*)+0x1168 > V [libjvm.so+0x6bb22c] ciObjectFactory::init_shared_objects()+0xc8c > V [libjvm.so+0x6bcc56] ciObjectFactory::initialize()+0x96 > V [libjvm.so+0x759535] CompileBroker::compiler_thread_loop()+0x1a5 > ``` > > As a result, the `Thread::current()->resource_area()` is growing already > before the allocation and there is no need to grow it anymore during the > compilation. As a result, no chunk allocations are detected by th... src/hotspot/share/ci/ciField.cpp line 238: > 236: ResourceMark rm; > 237: char buffer[256]; > 238: jio_snprintf(buffer, sizeof(buffer), "%s.%s", > declared_field->name()->as_utf8(), subfield->name()->as_utf8()); Instead, can we allocate 2 stack buffers for these names to be copied into? ------------- PR Review Comment: https://git.openjdk.org/valhalla/pull/2330#discussion_r3100520761
