1.1 --- a/src/share/vm/memory/cardTableModRefBS.cpp Mon Mar 02 16:37:04 2009 -0800
1.2 +++ b/src/share/vm/memory/cardTableModRefBS.cpp Fri Mar 06 13:50:14 2009 -0800
1.3 @@ -356,18 +356,62 @@
1.4 inline_write_ref_field(field, newVal);
1.5 }
1.6
1.7 +/*
1.8 + Claimed and deferred bits are used together in G1 during the evacuation
1.9 + pause. These bits can have the following state transitions:
1.10 + 1. The claimed bit can be put over any other card state. Except that
1.11 + the "dirty -> dirty and claimed" transition is checked for in
1.12 + G1 code and is not used.
1.13 + 2. Deferred bit can be set only if the previous state of the card
1.14 + was either clean or claimed. mark_card_deferred() is wait-free.
1.15 + We do not care if the operation is be successful because if
1.16 + it does not it will only result in duplicate entry in the update
1.17 + buffer because of the "cache-miss". So it's not worth spinning.
1.18 + */
1.19 +
1.20
1.21 bool CardTableModRefBS::claim_card(size_t card_index) {
1.22 jbyte val = _byte_map[card_index];
1.23 - if (val != claimed_card_val()) {
1.24 - jbyte res = Atomic::cmpxchg((jbyte) claimed_card_val(), &_byte_map[card_index], val);
1.25 - if (res == val)
1.26 + assert(val != dirty_card_val(), "Shouldn't claim a dirty card");
1.27 + while (val == clean_card_val() ||
1.28 + (val & (clean_card_mask_val() | claimed_card_val())) != claimed_card_val()) {
1.29 + jbyte new_val = val;
1.30 + if (val == clean_card_val()) {
1.31 + new_val = (jbyte)claimed_card_val();
1.32 + } else {
1.33 + new_val = val | (jbyte)claimed_card_val();
1.34 + }
1.35 + jbyte res = Atomic::cmpxchg(new_val, &_byte_map[card_index], val);
1.36 + if (res == val) {
1.37 return true;
1.38 - else return false;
1.39 + }
1.40 + val = res;
1.41 }
1.42 return false;
1.43 }
1.44
1.45 +bool CardTableModRefBS::mark_card_deferred(size_t card_index) {
1.46 + jbyte val = _byte_map[card_index];
1.47 + // It's already processed
1.48 + if ((val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val()) {
1.49 + return false;
1.50 + }
1.51 + // Cached bit can be installed either on a clean card or on a claimed card.
1.52 + jbyte new_val = val;
1.53 + if (val == clean_card_val()) {
1.54 + new_val = (jbyte)deferred_card_val();
1.55 + } else {
1.56 + if (val & claimed_card_val()) {
1.57 + new_val = val | (jbyte)deferred_card_val();
1.58 + }
1.59 + }
1.60 + if (new_val != val) {
1.61 + Atomic::cmpxchg(new_val, &_byte_map[card_index], val);
1.62 + }
1.63 + return true;
1.64 +}
1.65 +
1.66 +
1.67 void CardTableModRefBS::non_clean_card_iterate(Space* sp,
1.68 MemRegion mr,
1.69 DirtyCardToOopClosure* dcto_cl,
