src/share/vm/classfile/symbolTable.cpp

rev 11775 : [backport] 8241700: Shenandoah: Fold ShenandoahKeepAliveBarrier flag into ShenandoahSATBBarrier
Reviewed-by: shade
rev 11823 : Shenandoah: specialize String Table scans for better pause performance
Reviewed-by: rkennke, zgu

*** 719,729 ****
  static void ensure_string_alive(oop string) {
    // A lookup in the StringTable could return an object that was previously
    // considered dead. The SATB part of G1 needs to get notified about this
    // potential resurrection, otherwise the marking might not find the object.
  #if INCLUDE_ALL_GCS
!   if ((UseG1GC || (UseShenandoahGC && ShenandoahKeepAliveBarrier)) && string != NULL) {
      G1SATBCardTableModRefBS::enqueue(string);
    }
  #endif
  }
  
--- 719,729 ----
  static void ensure_string_alive(oop string) {
    // A lookup in the StringTable could return an object that was previously
    // considered dead. The SATB part of G1 needs to get notified about this
    // potential resurrection, otherwise the marking might not find the object.
  #if INCLUDE_ALL_GCS
!   if ((UseG1GC || (UseShenandoahGC && ShenandoahSATBBarrier)) && string != NULL) {
      G1SATBCardTableModRefBS::enqueue(string);
    }
  #endif
  }
  
*** 924,933 ****
--- 924,955 ----
      int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
      buckets_oops_do(f, start_idx, end_idx);
    }
  }
  
+ void StringTable::possibly_parallel_oops_do_shenandoah(OopClosure* f) {
+   const int limit = the_table()->table_size();
+ 
+   // ClaimChunkSize is too small for processing a String table during the pause
+   // efficiently: the atomic add costs dominate on many reasonable string tables.
+   // Recast the chunk size to give each GC worker about 10 chunks.
+   assert(UseShenandoahGC, "Only for Shenandoah");
+   const int chunk_size = MAX2<int>(ClaimChunkSize, limit / (ParallelGCThreads * 10));
+ 
+   for (;;) {
+     // Grab next set of buckets to scan
+     int start_idx = Atomic::add(chunk_size, &_parallel_claimed_idx) - chunk_size;
+     if (start_idx >= limit) {
+       // End of table
+       break;
+     }
+ 
+     int end_idx = MIN2(limit, start_idx + chunk_size);
+     buckets_oops_do(f, start_idx, end_idx);
+   }
+ }
+ 
  // This verification is part of Universe::verify() and needs to be quick.
  // See StringTable::verify_and_compare() below for exhaustive verification.
  void StringTable::verify() {
    for (int i = 0; i < the_table()->table_size(); ++i) {
      HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);