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diff src/share/vm/memory/defNewGeneration.cpp @ 1994:6cd6d394f280

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7001033: assert(gch->gc_cause() == GCCause::_scavenge_alot || !gch->incremental_collection_failed()) 7002546: regression on SpecJbb2005 on 7b118 comparing to 7b117 on small heaps Summary: Relaxed assertion checking related to incremental_collection_failed flag to allow for ExplicitGCInvokesConcurrent behaviour where we do not want a failing scavenge to bail to a stop-world collection. Parameterized incremental_collection_will_fail() so we can selectively use, or not use, as appropriate, the statistical prediction at specific use sites. This essentially reverts the scavenge bail-out logic to what it was prior to some recent changes that had inadvertently started using the statistical prediction which can be noisy in the presence of bursty loads. Added some associated verbose non-product debugging messages. Reviewed-by: johnc, tonyp
author ysr
date Tue, 07 Dec 2010 21:55:53 -0800
parents f95d63e2154a
children 74ee0db180fa
line wrap: on
line diff
--- a/src/share/vm/memory/defNewGeneration.cpp	Tue Dec 07 16:44:34 2010 -0800
+++ b/src/share/vm/memory/defNewGeneration.cpp	Tue Dec 07 21:55:53 2010 -0800
@@ -483,16 +483,17 @@
 // so we try to allocate the from-space, too.
 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
   HeapWord* result = NULL;
-  if (PrintGC && Verbose) {
+  if (Verbose && PrintGCDetails) {
     gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
-                  "  will_fail: %s"
-                  "  heap_lock: %s"
-                  "  free: " SIZE_FORMAT,
-                  size,
-               GenCollectedHeap::heap()->incremental_collection_will_fail() ? "true" : "false",
-               Heap_lock->is_locked() ? "locked" : "unlocked",
-               from()->free());
-    }
+                        "  will_fail: %s"
+                        "  heap_lock: %s"
+                        "  free: " SIZE_FORMAT,
+                        size,
+                        GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
+                          "true" : "false",
+                        Heap_lock->is_locked() ? "locked" : "unlocked",
+                        from()->free());
+  }
   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
     if (Heap_lock->owned_by_self() ||
         (SafepointSynchronize::is_at_safepoint() &&
@@ -534,6 +535,9 @@
   // from this generation, pass on collection; let the next generation
   // do it.
   if (!collection_attempt_is_safe()) {
+    if (Verbose && PrintGCDetails) {
+      gclog_or_tty->print(" :: Collection attempt not safe :: ");
+    }
     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
     return;
   }
@@ -821,6 +825,9 @@
 
 bool DefNewGeneration::collection_attempt_is_safe() {
   if (!to()->is_empty()) {
+    if (Verbose && PrintGCDetails) {
+      gclog_or_tty->print(" :: to is not empty :: ");
+    }
     return false;
   }
   if (_next_gen == NULL) {
@@ -843,10 +850,18 @@
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   if (full) {
     DEBUG_ONLY(seen_incremental_collection_failed = false;)
-    if (!collection_attempt_is_safe()) {
+    if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
+      if (Verbose && PrintGCDetails) {
+        gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
+                            GCCause::to_string(gch->gc_cause()));
+      }
       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
       set_should_allocate_from_space(); // we seem to be running out of space
     } else {
+      if (Verbose && PrintGCDetails) {
+        gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
+                            GCCause::to_string(gch->gc_cause()));
+      }
       gch->clear_incremental_collection_failed(); // We just did a full collection
       clear_should_allocate_from_space(); // if set
     }
@@ -860,11 +875,20 @@
     // a full collection in between.
     if (!seen_incremental_collection_failed &&
         gch->incremental_collection_failed()) {
+      if (Verbose && PrintGCDetails) {
+        gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
+                            GCCause::to_string(gch->gc_cause()));
+      }
       seen_incremental_collection_failed = true;
     } else if (seen_incremental_collection_failed) {
-      assert(gch->gc_cause() == GCCause::_scavenge_alot || !gch->incremental_collection_failed(),
+      if (Verbose && PrintGCDetails) {
+        gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
+                            GCCause::to_string(gch->gc_cause()));
+      }
+      assert(gch->gc_cause() == GCCause::_scavenge_alot ||
+             (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
+             !gch->incremental_collection_failed(),
              "Twice in a row");
-
       seen_incremental_collection_failed = false;
     }
 #endif // ASSERT