Mercurial > hg > truffle
diff src/share/vm/oops/instanceRefKlass.cpp @ 3917:eca1193ca245
4965777: GC changes to support use of discovered field for pending references
Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose.
Reviewed-by: jcoomes, mchung, stefank
| author | ysr |
|---|---|
| date | Wed, 07 Sep 2011 13:55:42 -0700 |
| parents | 2aa9ddbb9e60 |
| children | f94227b6117b |
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--- a/src/share/vm/oops/instanceRefKlass.cpp Wed Sep 07 15:00:13 2011 -0700 +++ b/src/share/vm/oops/instanceRefKlass.cpp Wed Sep 07 13:55:42 2011 -0700 @@ -56,9 +56,8 @@ if (!oopDesc::is_null(heap_oop)) { oop referent = oopDesc::decode_heap_oop_not_null(heap_oop); if (!referent->is_gc_marked() && - MarkSweep::ref_processor()-> - discover_reference(obj, ref->reference_type())) { - // reference already enqueued, referent will be traversed later + MarkSweep::ref_processor()->discover_reference(obj, ref->reference_type())) { + // reference was discovered, referent will be traversed later ref->instanceKlass::oop_follow_contents(obj); debug_only( if(TraceReferenceGC && PrintGCDetails) { @@ -76,8 +75,34 @@ MarkSweep::mark_and_push(referent_addr); } } - // treat next as normal oop. next is a link in the pending list. T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj); + if (ReferenceProcessor::pending_list_uses_discovered_field()) { + // Treat discovered as normal oop, if ref is not "active", + // i.e. if next is non-NULL. + T next_oop = oopDesc::load_heap_oop(next_addr); + if (!oopDesc::is_null(next_oop)) { // i.e. ref is not "active" + T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj); + debug_only( + if(TraceReferenceGC && PrintGCDetails) { + gclog_or_tty->print_cr(" Process discovered as normal " + INTPTR_FORMAT, discovered_addr); + } + ) + MarkSweep::mark_and_push(discovered_addr); + } + } else { +#ifdef ASSERT + // In the case of older JDKs which do not use the discovered + // field for the pending list, an inactive ref (next != NULL) + // must always have a NULL discovered field. + oop next = oopDesc::load_decode_heap_oop(next_addr); + oop discovered = java_lang_ref_Reference::discovered(obj); + assert(oopDesc::is_null(next) || oopDesc::is_null(discovered), + err_msg("Found an inactive reference " PTR_FORMAT " with a non-NULL discovered field", + obj)); +#endif + } + // treat next as normal oop. next is a link in the reference queue. debug_only( if(TraceReferenceGC && PrintGCDetails) { gclog_or_tty->print_cr(" Process next as normal " INTPTR_FORMAT, next_addr); @@ -130,13 +155,33 @@ PSParallelCompact::mark_and_push(cm, referent_addr); } } - // treat next as normal oop. next is a link in the pending list. T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj); - debug_only( - if(TraceReferenceGC && PrintGCDetails) { - gclog_or_tty->print_cr(" Process next as normal " INTPTR_FORMAT, next_addr); + if (ReferenceProcessor::pending_list_uses_discovered_field()) { + // Treat discovered as normal oop, if ref is not "active", + // i.e. if next is non-NULL. + T next_oop = oopDesc::load_heap_oop(next_addr); + if (!oopDesc::is_null(next_oop)) { // i.e. ref is not "active" + T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj); + debug_only( + if(TraceReferenceGC && PrintGCDetails) { + gclog_or_tty->print_cr(" Process discovered as normal " + INTPTR_FORMAT, discovered_addr); + } + ) + PSParallelCompact::mark_and_push(cm, discovered_addr); } - ) + } else { +#ifdef ASSERT + // In the case of older JDKs which do not use the discovered + // field for the pending list, an inactive ref (next != NULL) + // must always have a NULL discovered field. + T next = oopDesc::load_heap_oop(next_addr); + oop discovered = java_lang_ref_Reference::discovered(obj); + assert(oopDesc::is_null(next) || oopDesc::is_null(discovered), + err_msg("Found an inactive reference " PTR_FORMAT " with a non-NULL discovered field", + obj)); +#endif + } PSParallelCompact::mark_and_push(cm, next_addr); ref->instanceKlass::oop_follow_contents(cm, obj); } @@ -197,27 +242,53 @@ } #define InstanceRefKlass_SPECIALIZED_OOP_ITERATE(T, nv_suffix, contains) \ + T* disc_addr = (T*)java_lang_ref_Reference::discovered_addr(obj); \ if (closure->apply_to_weak_ref_discovered_field()) { \ - T* disc_addr = (T*)java_lang_ref_Reference::discovered_addr(obj); \ closure->do_oop##nv_suffix(disc_addr); \ } \ \ T* referent_addr = (T*)java_lang_ref_Reference::referent_addr(obj); \ T heap_oop = oopDesc::load_heap_oop(referent_addr); \ - if (!oopDesc::is_null(heap_oop) && contains(referent_addr)) { \ - ReferenceProcessor* rp = closure->_ref_processor; \ + ReferenceProcessor* rp = closure->_ref_processor; \ + if (!oopDesc::is_null(heap_oop)) { \ oop referent = oopDesc::decode_heap_oop_not_null(heap_oop); \ if (!referent->is_gc_marked() && (rp != NULL) && \ rp->discover_reference(obj, reference_type())) { \ return size; \ - } else { \ + } else if (contains(referent_addr)) { \ /* treat referent as normal oop */ \ SpecializationStats::record_do_oop_call##nv_suffix(SpecializationStats::irk);\ closure->do_oop##nv_suffix(referent_addr); \ } \ } \ + T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj); \ + if (ReferenceProcessor::pending_list_uses_discovered_field()) { \ + T next_oop = oopDesc::load_heap_oop(next_addr); \ + /* Treat discovered as normal oop, if ref is not "active" (next non-NULL) */\ + if (!oopDesc::is_null(next_oop) && contains(disc_addr)) { \ + /* i.e. ref is not "active" */ \ + debug_only( \ + if(TraceReferenceGC && PrintGCDetails) { \ + gclog_or_tty->print_cr(" Process discovered as normal " \ + INTPTR_FORMAT, disc_addr); \ + } \ + ) \ + SpecializationStats::record_do_oop_call##nv_suffix(SpecializationStats::irk);\ + closure->do_oop##nv_suffix(disc_addr); \ + } \ + } else { \ + /* In the case of older JDKs which do not use the discovered field for */ \ + /* the pending list, an inactive ref (next != NULL) must always have a */ \ + /* NULL discovered field. */ \ + debug_only( \ + T next_oop = oopDesc::load_heap_oop(next_addr); \ + T disc_oop = oopDesc::load_heap_oop(disc_addr); \ + assert(oopDesc::is_null(next_oop) || oopDesc::is_null(disc_oop), \ + err_msg("Found an inactive reference " PTR_FORMAT " with a non-NULL" \ + "discovered field", obj)); \ + ) \ + } \ /* treat next as normal oop */ \ - T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj); \ if (contains(next_addr)) { \ SpecializationStats::record_do_oop_call##nv_suffix(SpecializationStats::irk); \ closure->do_oop##nv_suffix(next_addr); \ @@ -306,8 +377,37 @@ pm->claim_or_forward_depth(referent_addr); } } - // treat next as normal oop + // Treat discovered as normal oop, if ref is not "active", + // i.e. if next is non-NULL. T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj); + if (ReferenceProcessor::pending_list_uses_discovered_field()) { + T next_oop = oopDesc::load_heap_oop(next_addr); + if (!oopDesc::is_null(next_oop)) { // i.e. ref is not "active" + T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj); + debug_only( + if(TraceReferenceGC && PrintGCDetails) { + gclog_or_tty->print_cr(" Process discovered as normal " + INTPTR_FORMAT, discovered_addr); + } + ) + if (PSScavenge::should_scavenge(discovered_addr)) { + pm->claim_or_forward_depth(discovered_addr); + } + } + } else { +#ifdef ASSERT + // In the case of older JDKs which do not use the discovered + // field for the pending list, an inactive ref (next != NULL) + // must always have a NULL discovered field. + oop next = oopDesc::load_decode_heap_oop(next_addr); + oop discovered = java_lang_ref_Reference::discovered(obj); + assert(oopDesc::is_null(next) || oopDesc::is_null(discovered), + err_msg("Found an inactive reference " PTR_FORMAT " with a non-NULL discovered field", + obj)); +#endif + } + + // Treat next as normal oop; next is a link in the reference queue. if (PSScavenge::should_scavenge(next_addr)) { pm->claim_or_forward_depth(next_addr); }