Mercurial > hg > truffle
diff src/share/vm/gc_implementation/shared/coTracker.hpp @ 362:f8199438385b
Merge
author | apetrusenko |
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date | Wed, 17 Sep 2008 16:49:18 +0400 |
parents | 37f87013dfd8 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/shared/coTracker.hpp Wed Sep 17 16:49:18 2008 +0400 @@ -0,0 +1,181 @@ +/* + * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +// COTracker keeps track of the concurrent overhead of a GC thread. + +// A thread that needs to be tracked must, itself, start up its +// tracker with the start() method and then call the update() method +// at regular intervals. What the tracker does is to calculate the +// concurrent overhead of a process at a given update period. The +// tracker starts and when is detects that it has exceeded the given +// period, it calculates the duration of the period in wall-clock time +// and the duration of the period in vtime (i.e. how much time the +// concurrent processes really took up during this period). The ratio +// of the latter over the former is the concurrent overhead of that +// process for that period over a single CPU. This overhead is stored +// on the tracker, "timestamped" with the wall-clock time of the end +// of the period. When the concurrent overhead of this process needs +// to be queried, this last "reading" provides a good approximation +// (we assume that the concurrent overhead of a particular thread +// stays largely constant over time). The timestamp is necessary to +// detect when the process has stopped working and the recorded +// reading hasn't been updated for some time. + +// Each concurrent GC thread is considered to be part of a "group" +// (i.e. any available concurrent marking threads are part of the +// "concurrent marking thread group"). A COTracker is associated with +// a single group at construction-time. It's up to each collector to +// decide how groups will be mapped to such an id (ids should start +// from 0 and be consecutive; there's a hardcoded max group num +// defined on the GCOverheadTracker class). The notion of a group has +// been introduced to be able to identify how much overhead was +// imposed by each group, instead of getting a single value that +// covers all concurrent overhead. + +class COTracker { +private: + // It indicates whether this tracker is enabled or not. When the + // tracker is disabled, then it returns 0.0 as the latest concurrent + // overhead and several methods (reset, start, and update) are not + // supposed to be called on it. This enabling / disabling facility + // is really provided to make a bit more explicit in the code when a + // particulary tracker of a processes that doesn't run all the time + // (e.g. concurrent marking) is supposed to be used and not it's not. + bool _enabled; + + // The ID of the group associated with this tracker. + int _group; + + // The update period of the tracker. A new value for the concurrent + // overhead of the associated process will be made at intervals no + // smaller than this. + double _update_period_sec; + + // The start times (both wall-block time and vtime) of the current + // interval. + double _period_start_time_sec; + double _period_start_vtime_sec; + + // Number seq of the concurrent overhead readings within a period + NumberSeq _conc_overhead_seq; + + // The latest reading of the concurrent overhead (over a single CPU) + // imposed by the associated concurrent thread, made available at + // the indicated wall-clock time. + double _conc_overhead; + double _time_stamp_sec; + + // The number of CPUs that the host machine has (for convenience + // really, as we'd have to keep translating it into a double) + static double _cpu_number; + + // Fields that keep a list of all trackers created. This is useful, + // since it allows us to sum up the concurrent overhead without + // having to write code for a specific collector to broadcast a + // request to all its concurrent processes. + COTracker* _next; + static COTracker* _head; + + // It indicates that a new period is starting by updating the + // _period_start_time_sec and _period_start_vtime_sec fields. + void resetPeriod(double now_sec, double vnow_sec); + // It updates the latest concurrent overhead reading, taken at a + // given wall-clock time. + void setConcOverhead(double time_stamp_sec, double conc_overhead); + + // It determines whether the time stamp of the latest concurrent + // overhead reading is out of date or not. + bool outOfDate(double now_sec) { + // The latest reading is considered out of date, if it was taken + // 1.2x the update period. + return (now_sec - _time_stamp_sec) > 1.2 * _update_period_sec; + } + +public: + // The constructor which associates the tracker with a group ID. + COTracker(int group); + + // Methods to enable / disable the tracker and query whether it is enabled. + void enable() { _enabled = true; } + void disable() { _enabled = false; } + bool enabled() { return _enabled; } + + // It resets the tracker and sets concurrent overhead reading to be + // the given parameter and the associated time stamp to be now. + void reset(double starting_conc_overhead = 0.0); + // The tracker starts tracking. IT should only be called from the + // concurrent thread that is tracked by this tracker. + void start(); + // It updates the tracker and, if the current period is longer than + // the update period, the concurrent overhead reading will be + // updated. force_end being true indicates that it's the last call + // to update() by this process before the tracker is disabled (the + // tracker can be re-enabled later if necessary). It should only be + // called from the concurrent thread that is tracked by this tracker + // and while the thread has joined the STS. + void update(bool force_end = false); + // It adjusts the contents of the tracker to take into account a STW + // pause. + void updateForSTW(double start_sec, double end_sec); + + // It returns the last concurrent overhead reading over a single + // CPU. If the reading is out of date, or the tracker is disabled, + // it returns 0.0. + double concCPUOverhead(double now_sec) { + if (!_enabled || outOfDate(now_sec)) + return 0.0; + else + return _conc_overhead; + } + + // It returns the last concurrent overhead reading over all CPUs + // that the host machine has. If the reading is out of date, or the + // tracker is disabled, it returns 0.0. + double concOverhead(double now_sec) { + return concCPUOverhead(now_sec) / _cpu_number; + } + + double predConcOverhead(); + + void resetPred(); + + // statics + + // It notifies all trackers about a STW pause. + static void updateAllForSTW(double start_sec, double end_sec); + + // It returns the sum of the concurrent overhead readings of all + // available (and enabled) trackers for the given time stamp. The + // overhead is over all the CPUs of the host machine. + + static double totalConcOverhead(double now_sec); + // Like the previous method, but it also sums up the overheads per + // group number. The length of the co_per_group array must be at + // least as large group_num + static double totalConcOverhead(double now_sec, + size_t group_num, + double* co_per_group); + + static double totalPredConcOverhead(); +};