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/*
* Copyright (c) 2014, 2019, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_RUNTIME_RTMLOCKING_HPP
#define SHARE_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 {
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];
static const char* _abortX_desc[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; }
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) const;
void print() const;
};
#endif // SHARE_RUNTIME_RTMLOCKING_HPP
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