/*

 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

#ifndef SHARE_VM_RUNTIME_RTMLOCKING_HPP

#define SHARE_VM_RUNTIME_RTMLOCKING_HPP

// Generate RTM (Restricted Transactional Memory) locking code for all inflated

// locks when "UseRTMLocking" option is on with normal locking mechanism as fall back

// handler.

//

// On abort/lock busy the lock will be retried a fixed number of times under RTM

// as specified by "RTMRetryCount" option. The locks which abort too often

// can be auto tuned or manually tuned.

//

// Auto-tuning can be done on an option like UseRTMDeopt and it will need abort

// ratio calculation for each lock. The abort ratio will be calculated after

// "RTMAbortThreshold" number of aborts is reached. The formulas are:

//

//     Aborted transactions = abort_count * 100

//     All transactions = total_count *  RTMTotalCountIncrRate

//

//     Aborted transactions >= All transactions * RTMAbortRatio

//

// If "UseRTMDeopt" is on and the aborts ratio reaches "RTMAbortRatio"

// the method containing the lock will be deoptimized and recompiled with

// all locks as normal locks. If the abort ratio continues to remain low after

// "RTMLockingThreshold" locks are attempted, then the method will be deoptimized

// and recompiled with all locks as RTM locks without abort ratio calculation code.

// The abort ratio calculation can be delayed by specifying flag

// -XX:RTMLockingCalculationDelay in millisecond.

//

// For manual tuning the abort statistics for each lock needs to be provided

// to the user on some JVM option like "PrintPreciseRTMLockingStatistics".

// Based on the abort statistics users can create a .hotspot_compiler file

// or use -XX:CompileCommand=option,class::method,NoRTMLockEliding

// to specify for which methods to disable RTM locking.

//

// When UseRTMForStackLocks option is enabled along with UseRTMLocking option,

// the RTM locking code is generated for stack locks too.

// The retries, auto-tuning support and rtm locking statistics are all

// supported for stack locks just like inflated locks.

// RTM locking counters

class RTMLockingCounters VALUE_OBJ_CLASS_SPEC {

 private:

  uintx _total_count; // Total RTM locks count

  uintx _abort_count; // Total aborts count

 public:

  enum { ABORT_STATUS_LIMIT = 6 };

  // Counters per RTM Abort Status. Incremented with +PrintPreciseRTMLockingStatistics

  // RTM uses the EAX register to communicate abort status to software.

  // Following an RTM abort the EAX register has the following definition.

  //

  //   EAX register bit position   Meaning

  //     0     Set if abort caused by XABORT instruction.

  //     1     If set, the transaction may succeed on a retry. This bit is always clear if bit 0 is set.

  //     2     Set if another logical processor conflicted with a memory address that was part of the transaction that aborted.

  //     3     Set if an internal buffer overflowed.

  //     4     Set if a debug breakpoint was hit.

  //     5     Set if an abort occurred during execution of a nested transaction.

 private:

  uintx _abortX_count[ABORT_STATUS_LIMIT];

 public:

  static uintx _calculation_flag;

  static uintx* rtm_calculation_flag_addr() { return &_calculation_flag; }

  static void init();

  RTMLockingCounters() : _total_count(0), _abort_count(0) {

    for (int i = 0; i < ABORT_STATUS_LIMIT; i++) {

      _abortX_count[i] = 0;

    }

  }

  uintx* total_count_addr()               { return &_total_count; }

  uintx* abort_count_addr()               { return &_abort_count; }

  uintx* abortX_count_addr()              { return &_abortX_count[0]; }

  static int total_count_offset()         { return (int)offset_of(RTMLockingCounters, _total_count); }

  static int abort_count_offset()         { return (int)offset_of(RTMLockingCounters, _abort_count); }

  static int abortX_count_offset()        { return (int)offset_of(RTMLockingCounters, _abortX_count[0]); }

  bool nonzero() {  return (_abort_count + _total_count) > 0; }

  void print_on(outputStream* st);

  void print() { print_on(tty); }

};

#endif // SHARE_VM_RUNTIME_RTMLOCKING_HPP