Mon, 09 Jun 2008 11:51:19 -0400
6687581: Make CMS work with compressed oops
Summary: Make FreeChunk read markword instead of LSB in _klass pointer to indicate that it's a FreeChunk for compressed oops.
Reviewed-by: ysr, jmasa
duke@435 | 1 | /* |
duke@435 | 2 | * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. |
duke@435 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
duke@435 | 4 | * |
duke@435 | 5 | * This code is free software; you can redistribute it and/or modify it |
duke@435 | 6 | * under the terms of the GNU General Public License version 2 only, as |
duke@435 | 7 | * published by the Free Software Foundation. |
duke@435 | 8 | * |
duke@435 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
duke@435 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
duke@435 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
duke@435 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
duke@435 | 13 | * accompanied this code). |
duke@435 | 14 | * |
duke@435 | 15 | * You should have received a copy of the GNU General Public License version |
duke@435 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
duke@435 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
duke@435 | 18 | * |
duke@435 | 19 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
duke@435 | 20 | * CA 95054 USA or visit www.sun.com if you need additional information or |
duke@435 | 21 | * have any questions. |
duke@435 | 22 | * |
duke@435 | 23 | */ |
duke@435 | 24 | |
duke@435 | 25 | // Should this header be preserved during GC? |
duke@435 | 26 | inline bool markOopDesc::must_be_preserved_with_bias(oop obj_containing_mark) const { |
duke@435 | 27 | assert(UseBiasedLocking, "unexpected"); |
duke@435 | 28 | if (has_bias_pattern()) { |
duke@435 | 29 | // Will reset bias at end of collection |
duke@435 | 30 | // Mark words of biased and currently locked objects are preserved separately |
duke@435 | 31 | return false; |
duke@435 | 32 | } |
duke@435 | 33 | markOop prototype_header = prototype_for_object(obj_containing_mark); |
duke@435 | 34 | if (prototype_header->has_bias_pattern()) { |
duke@435 | 35 | // Individual instance which has its bias revoked; must return |
duke@435 | 36 | // true for correctness |
duke@435 | 37 | return true; |
duke@435 | 38 | } |
duke@435 | 39 | return (!is_unlocked() || !has_no_hash()); |
duke@435 | 40 | } |
duke@435 | 41 | |
duke@435 | 42 | // Should this header (including its age bits) be preserved in the |
duke@435 | 43 | // case of a promotion failure during scavenge? |
duke@435 | 44 | inline bool markOopDesc::must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const { |
duke@435 | 45 | assert(UseBiasedLocking, "unexpected"); |
duke@435 | 46 | // We don't explicitly save off the mark words of biased and |
duke@435 | 47 | // currently-locked objects during scavenges, so if during a |
duke@435 | 48 | // promotion failure we encounter either a biased mark word or a |
duke@435 | 49 | // klass which still has a biasable prototype header, we have to |
duke@435 | 50 | // preserve the mark word. This results in oversaving, but promotion |
duke@435 | 51 | // failures are rare, and this avoids adding more complex logic to |
duke@435 | 52 | // the scavengers to call new variants of |
duke@435 | 53 | // BiasedLocking::preserve_marks() / restore_marks() in the middle |
duke@435 | 54 | // of a scavenge when a promotion failure has first been detected. |
duke@435 | 55 | if (has_bias_pattern() || |
duke@435 | 56 | prototype_for_object(obj_containing_mark)->has_bias_pattern()) { |
duke@435 | 57 | return true; |
duke@435 | 58 | } |
duke@435 | 59 | return (this != prototype()); |
duke@435 | 60 | } |
duke@435 | 61 | |
duke@435 | 62 | // Should this header (including its age bits) be preserved in the |
duke@435 | 63 | // case of a scavenge in which CMS is the old generation? |
duke@435 | 64 | inline bool markOopDesc::must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const { |
duke@435 | 65 | assert(UseBiasedLocking, "unexpected"); |
duke@435 | 66 | // CMS scavenges preserve mark words in similar fashion to promotion failures; see above |
duke@435 | 67 | if (has_bias_pattern() || |
duke@435 | 68 | klass_of_obj_containing_mark->klass_part()->prototype_header()->has_bias_pattern()) { |
duke@435 | 69 | return true; |
duke@435 | 70 | } |
duke@435 | 71 | return (this != prototype()); |
duke@435 | 72 | } |
duke@435 | 73 | |
duke@435 | 74 | inline markOop markOopDesc::prototype_for_object(oop obj) { |
duke@435 | 75 | #ifdef ASSERT |
duke@435 | 76 | markOop prototype_header = obj->klass()->klass_part()->prototype_header(); |
duke@435 | 77 | assert(prototype_header == prototype() || prototype_header->has_bias_pattern(), "corrupt prototype header"); |
duke@435 | 78 | #endif |
duke@435 | 79 | return obj->klass()->klass_part()->prototype_header(); |
duke@435 | 80 | } |