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diff src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp @ 889:15c5903cf9e1

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6865703: G1: Parallelize hot card cache cleanup Summary: Have the GC worker threads clear the hot card cache in parallel by having each worker thread claim a chunk of the card cache and process the cards in that chunk. The size of the chunks that each thread will claim is determined at VM initialization from the size of the card cache and the number of worker threads. Reviewed-by: jmasa, tonyp
author johnc
date Mon, 03 Aug 2009 12:59:30 -0700
parents bd02caa94611
children 6cb8e9df7174
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp	Sun Aug 02 22:33:27 2009 -0700
+++ b/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp	Mon Aug 03 12:59:30 2009 -0700
@@ -57,8 +57,8 @@
 }
 
 void ConcurrentG1Refine::init() {
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
   if (G1ConcRSLogCacheSize > 0 || G1ConcRSCountTraversals) {
-    G1CollectedHeap* g1h = G1CollectedHeap::heap();
     _n_card_counts =
       (unsigned) (g1h->g1_reserved_obj_bytes() >> CardTableModRefBS::card_shift);
     _card_counts = NEW_C_HEAP_ARRAY(unsigned char, _n_card_counts);
@@ -83,6 +83,12 @@
     _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size);
     _n_hot = 0;
     _hot_cache_idx = 0;
+
+    // For refining the cards in the hot cache in parallel
+    int n_workers = (ParallelGCThreads > 0 ?
+                        g1h->workers()->total_workers() : 1);
+    _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers);
+    _hot_cache_par_claimed_idx = 0;
   }
 }
 
@@ -161,17 +167,23 @@
 
 void ConcurrentG1Refine::clean_up_cache(int worker_i, G1RemSet* g1rs) {
   assert(!use_cache(), "cache should be disabled");
-  int start_ind = _hot_cache_idx-1;
-  for (int i = 0; i < _n_hot; i++) {
-    int ind = start_ind - i;
-    if (ind < 0) ind = ind + _hot_cache_size;
-    jbyte* entry = _hot_cache[ind];
-    if (entry != NULL) {
-      g1rs->concurrentRefineOneCard(entry, worker_i);
+  int start_idx;
+
+  while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once
+    int end_idx = start_idx + _hot_cache_par_chunk_size;
+
+    if (start_idx ==
+        Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) {
+      // The current worker has successfully claimed the chunk [start_idx..end_idx)
+      end_idx = MIN2(end_idx, _n_hot);
+      for (int i = start_idx; i < end_idx; i++) {
+        jbyte* entry = _hot_cache[i];
+        if (entry != NULL) {
+          g1rs->concurrentRefineOneCard(entry, worker_i);
+        }
+      }
     }
   }
-  _n_hot = 0;
-  _hot_cache_idx = 0;
 }
 
 void ConcurrentG1Refine::clear_and_record_card_counts() {