Mercurial > hg > graal-jvmci-8
diff src/share/vm/opto/runtime.cpp @ 1027:39b01ab7035a
6888898: CMS: ReduceInitialCardMarks unsafe in the presence of cms precleaning
6889757: G1: enable card mark elision for initializing writes from compiled code (ReduceInitialCardMarks)
Summary: Defer the (compiler-elided) card-mark upon a slow-path allocation until after the store and before the next subsequent safepoint; G1 now answers yes to can_elide_tlab_write_barriers().
Reviewed-by: jcoomes, kvn, never
author | ysr |
---|---|
date | Fri, 16 Oct 2009 02:05:46 -0700 |
parents | 98cb887364d3 |
children | e66fd840cb6b |
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--- a/src/share/vm/opto/runtime.cpp Wed Oct 07 19:01:55 2009 -0400 +++ b/src/share/vm/opto/runtime.cpp Fri Oct 16 02:05:46 2009 -0700 @@ -143,18 +143,20 @@ // We failed the fast-path allocation. Now we need to do a scavenge or GC // and try allocation again. -void OptoRuntime::do_eager_card_mark(JavaThread* thread) { +void OptoRuntime::maybe_defer_card_mark(JavaThread* thread) { // After any safepoint, just before going back to compiled code, - // we perform a card mark. This lets the compiled code omit - // card marks for initialization of new objects. - // Keep this code consistent with GraphKit::store_barrier. + // we inform the GC that we will be doing initializing writes to + // this object in the future without emitting card-marks, so + // GC may take any compensating steps. + // NOTE: Keep this code consistent with GraphKit::store_barrier. oop new_obj = thread->vm_result(); if (new_obj == NULL) return; assert(Universe::heap()->can_elide_tlab_store_barriers(), "compiler must check this first"); - new_obj = Universe::heap()->new_store_barrier(new_obj); + // GC may decide to give back a safer copy of new_obj. + new_obj = Universe::heap()->defer_store_barrier(thread, new_obj); thread->set_vm_result(new_obj); } @@ -197,8 +199,8 @@ JRT_BLOCK_END; if (GraphKit::use_ReduceInitialCardMarks()) { - // do them now so we don't have to do them on the fast path - do_eager_card_mark(thread); + // inform GC that we won't do card marks for initializing writes. + maybe_defer_card_mark(thread); } JRT_END @@ -236,8 +238,8 @@ JRT_BLOCK_END; if (GraphKit::use_ReduceInitialCardMarks()) { - // do them now so we don't have to do them on the fast path - do_eager_card_mark(thread); + // inform GC that we won't do card marks for initializing writes. + maybe_defer_card_mark(thread); } JRT_END