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/*
* Copyright (c) 2001, 2009, 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.
*
*/
#include "incls/_precompiled.incl"
#include "incls/_g1MMUTracker.cpp.incl"
#define _DISABLE_MMU 0
// can't rely on comparing doubles with tolerating a small margin for error
#define SMALL_MARGIN 0.0000001
#define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN )
#define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2))
#define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1))
/***** ALL TIMES ARE IN SECS!!!!!!! *****/
G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
_time_slice(time_slice),
_max_gc_time(max_gc_time) { }
G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :
G1MMUTracker(time_slice, max_gc_time),
_head_index(0),
_tail_index(trim_index(_head_index+1)),
_no_entries(0) { }
void G1MMUTrackerQueue::remove_expired_entries(double current_time) {
double limit = current_time - _time_slice;
while (_no_entries > 0) {
if (is_double_geq(limit, _array[_tail_index].end_time())) {
_tail_index = trim_index(_tail_index + 1);
--_no_entries;
} else
return;
}
guarantee(_no_entries == 0, "should have no entries in the array");
}
double G1MMUTrackerQueue::calculate_gc_time(double current_time) {
double gc_time = 0.0;
double limit = current_time - _time_slice;
for (int i = 0; i < _no_entries; ++i) {
int index = trim_index(_tail_index + i);
G1MMUTrackerQueueElem *elem = &_array[index];
if (elem->end_time() > limit) {
if (elem->start_time() > limit)
gc_time += elem->duration();
else
gc_time += elem->end_time() - limit;
}
}
return gc_time;
}
void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {
double longest_allowed = longest_pause_internal(start);
if (longest_allowed < 0.0)
longest_allowed = 0.0;
double duration = end - start;
remove_expired_entries(end);
if (_no_entries == QueueLength) {
// OK, right now when we fill up we bomb out
// there are a few ways of dealing with this "gracefully"
// increase the array size (:-)
// remove the oldest entry (this might allow more GC time for
// the time slice than what's allowed)
// consolidate the two entries with the minimum gap between them
// (this might allow less GC time than what's allowed)
guarantee(NOT_PRODUCT(ScavengeALot ||) G1UseFixedWindowMMUTracker,
"array full, currently we can't recover unless +G1UseFixedWindowMMUTracker");
// In the case where ScavengeALot is true, such overflow is not
// uncommon; in such cases, we can, without much loss of precision
// or performance (we are GC'ing most of the time anyway!),
// simply overwrite the oldest entry in the tracker: this
// is also the behaviour when G1UseFixedWindowMMUTracker is enabled.
_head_index = trim_index(_head_index + 1);
assert(_head_index == _tail_index, "Because we have a full circular buffer");
_tail_index = trim_index(_tail_index + 1);
} else {
_head_index = trim_index(_head_index + 1);
++_no_entries;
}
_array[_head_index] = G1MMUTrackerQueueElem(start, end);
}
// basically the _internal call does not remove expired entries
// this is for trying things out in the future and a couple
// of other places (debugging)
double G1MMUTrackerQueue::longest_pause(double current_time) {
if (_DISABLE_MMU)
return _max_gc_time;
MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
remove_expired_entries(current_time);
return longest_pause_internal(current_time);
}
double G1MMUTrackerQueue::longest_pause_internal(double current_time) {
double target_time = _max_gc_time;
while( 1 ) {
double gc_time =
calculate_gc_time(current_time + target_time);
double diff = target_time + gc_time - _max_gc_time;
if (!is_double_leq_0(diff)) {
target_time -= diff;
if (is_double_leq_0(target_time)) {
target_time = -1.0;
break;
}
} else {
break;
}
}
return target_time;
}
// basically the _internal call does not remove expired entries
// this is for trying things out in the future and a couple
// of other places (debugging)
double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
if (_DISABLE_MMU)
return 0.0;
MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
remove_expired_entries(current_time);
return when_internal(current_time, pause_time);
}
double G1MMUTrackerQueue::when_internal(double current_time,
double pause_time) {
// if the pause is over the maximum, just assume that it's the maximum
double adjusted_pause_time =
(pause_time > max_gc_time()) ? max_gc_time() : pause_time;
double earliest_end = current_time + adjusted_pause_time;
double limit = earliest_end - _time_slice;
double gc_time = calculate_gc_time(earliest_end);
double diff = gc_time + adjusted_pause_time - max_gc_time();
if (is_double_leq_0(diff))
return 0.0;
int index = _tail_index;
while ( 1 ) {
G1MMUTrackerQueueElem *elem = &_array[index];
if (elem->end_time() > limit) {
if (elem->start_time() > limit)
diff -= elem->duration();
else
diff -= elem->end_time() - limit;
if (is_double_leq_0(diff))
return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
}
index = trim_index(index+1);
guarantee(index != trim_index(_head_index + 1), "should not go past head");
}
}
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