1 /*
   2  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // An NmethodSweeper is an incremental cleaner for:
  26 //    - cleanup inline caches
  27 //    - reclamation of unreferences zombie nmethods
  28 //
  29 
  30 class NMethodSweeper : public AllStatic {
  31   static long      _traversals;   // Stack traversal count
  32   static nmethod*  _current;      // Current nmethod
  33   static int       _seen;         // Nof. nmethod we have currently processed in current pass of CodeCache
  34 
  35   static volatile int      _invocations;   // No. of invocations left until we are completed with this pass
  36   static volatile int      _sweep_started; // Flag to control conc sweeper
  37 
  38   static bool      _rescan;          // Indicates that we should do a full rescan of the
  39                                      // of the code cache looking for work to do.
  40   static bool      _do_sweep;        // Flag to skip the conc sweep if no stack scan happened
  41   static int       _locked_seen;     // Number of locked nmethods encountered during the scan
  42   static int       _not_entrant_seen_on_stack; // Number of not entrant nmethod were are still on stack
  43 
  44   static bool      _was_full;        // remember if we did emergency unloading
  45   static jint      _advise_to_sweep; // flag to indicate code cache getting full
  46   static jlong     _last_was_full;   // timestamp of last emergency unloading
  47   static uint      _highest_marked;   // highest compile id dumped at last emergency unloading
  48   static long      _was_full_traversal;   // trav number at last emergency unloading
  49 
  50   static void process_nmethod(nmethod *nm);
  51 
  52   static void log_sweep(const char* msg, const char* format = NULL, ...);
  53 
  54  public:
  55   static long traversal_count() { return _traversals; }
  56 
  57   static void scan_stacks();      // Invoked at the end of each safepoint
  58   static void sweep_code_cache(); // Concurrent part of sweep job
  59   static void possibly_sweep();   // Compiler threads call this to sweep
  60 
  61   static void notify(nmethod* nm) {
  62     // Perform a full scan of the code cache from the beginning.  No
  63     // need to synchronize the setting of this flag since it only
  64     // changes to false at safepoint so we can never overwrite it with false.
  65      _rescan = true;
  66   }
  67 
  68   static void handle_full_code_cache(bool is_full); // Called by compilers who fail to allocate
  69   static void speculative_disconnect_nmethods(bool was_full);   // Called by vm op to deal with alloc failure
  70 
  71   static void set_was_full(bool state) { _was_full = state; }
  72   static bool was_full() { return _was_full; }
  73 };