97a51c5c2a
Use RTM for inflated locks and stack locks. Reviewed-by: iveresov, twisti, roland, dcubed
114 lines
5.0 KiB
C++
114 lines
5.0 KiB
C++
/*
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* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_RUNTIME_RTMLOCKING_HPP
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#define SHARE_VM_RUNTIME_RTMLOCKING_HPP
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// Generate RTM (Restricted Transactional Memory) locking code for all inflated
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// locks when "UseRTMLocking" option is on with normal locking mechanism as fall back
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// handler.
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//
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// On abort/lock busy the lock will be retried a fixed number of times under RTM
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// as specified by "RTMRetryCount" option. The locks which abort too often
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// can be auto tuned or manually tuned.
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//
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// Auto-tuning can be done on an option like UseRTMDeopt and it will need abort
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// ratio calculation for each lock. The abort ratio will be calculated after
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// "RTMAbortThreshold" number of aborts is reached. The formulas are:
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//
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// Aborted transactions = abort_count * 100
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// All transactions = total_count * RTMTotalCountIncrRate
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//
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// Aborted transactions >= All transactions * RTMAbortRatio
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//
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// If "UseRTMDeopt" is on and the aborts ratio reaches "RTMAbortRatio"
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// the method containing the lock will be deoptimized and recompiled with
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// all locks as normal locks. If the abort ratio continues to remain low after
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// "RTMLockingThreshold" locks are attempted, then the method will be deoptimized
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// and recompiled with all locks as RTM locks without abort ratio calculation code.
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// The abort ratio calculation can be delayed by specifying flag
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// -XX:RTMLockingCalculationDelay in millisecond.
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//
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// For manual tuning the abort statistics for each lock needs to be provided
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// to the user on some JVM option like "PrintPreciseRTMLockingStatistics".
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// Based on the abort statistics users can create a .hotspot_compiler file
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// or use -XX:CompileCommand=option,class::method,NoRTMLockEliding
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// to specify for which methods to disable RTM locking.
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//
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// When UseRTMForStackLocks option is enabled along with UseRTMLocking option,
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// the RTM locking code is generated for stack locks too.
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// The retries, auto-tuning support and rtm locking statistics are all
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// supported for stack locks just like inflated locks.
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// RTM locking counters
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class RTMLockingCounters VALUE_OBJ_CLASS_SPEC {
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private:
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uintx _total_count; // Total RTM locks count
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uintx _abort_count; // Total aborts count
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public:
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enum { ABORT_STATUS_LIMIT = 6 };
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// Counters per RTM Abort Status. Incremented with +PrintPreciseRTMLockingStatistics
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// RTM uses the EAX register to communicate abort status to software.
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// Following an RTM abort the EAX register has the following definition.
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//
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// EAX register bit position Meaning
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// 0 Set if abort caused by XABORT instruction.
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// 1 If set, the transaction may succeed on a retry. This bit is always clear if bit 0 is set.
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// 2 Set if another logical processor conflicted with a memory address that was part of the transaction that aborted.
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// 3 Set if an internal buffer overflowed.
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// 4 Set if a debug breakpoint was hit.
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// 5 Set if an abort occurred during execution of a nested transaction.
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private:
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uintx _abortX_count[ABORT_STATUS_LIMIT];
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public:
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static uintx _calculation_flag;
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static uintx* rtm_calculation_flag_addr() { return &_calculation_flag; }
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static void init();
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RTMLockingCounters() : _total_count(0), _abort_count(0) {
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for (int i = 0; i < ABORT_STATUS_LIMIT; i++) {
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_abortX_count[i] = 0;
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}
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}
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uintx* total_count_addr() { return &_total_count; }
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uintx* abort_count_addr() { return &_abort_count; }
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uintx* abortX_count_addr() { return &_abortX_count[0]; }
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static int total_count_offset() { return (int)offset_of(RTMLockingCounters, _total_count); }
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static int abort_count_offset() { return (int)offset_of(RTMLockingCounters, _abort_count); }
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static int abortX_count_offset() { return (int)offset_of(RTMLockingCounters, _abortX_count[0]); }
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bool nonzero() { return (_abort_count + _total_count) > 0; }
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void print_on(outputStream* st);
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void print() { print_on(tty); }
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};
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#endif // SHARE_VM_RUNTIME_RTMLOCKING_HPP
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