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53b235e1 | 1 | /******************************************************************************* |
e471302a | 2 | * Copyright (c) 2014 Ericsson |
53b235e1 MK |
3 | * |
4 | * All rights reserved. This program and the accompanying materials are made | |
5 | * available under the terms of the Eclipse Public License v1.0 which | |
6 | * accompanies this distribution, and is available at | |
7 | * http://www.eclipse.org/legal/epl-v10.html | |
8 | * | |
f0414df8 | 9 | * Contributors: |
e471302a | 10 | * Alexandre Montplaisir - Renamed/extracted from CtfTraceManager |
53b235e1 | 11 | *******************************************************************************/ |
e471302a | 12 | |
2bdf0193 | 13 | package org.eclipse.tracecompass.tmf.ctf.core; |
53b235e1 MK |
14 | |
15 | import java.util.ArrayList; | |
16 | import java.util.HashMap; | |
17 | import java.util.Random; | |
6a0ec7bc AM |
18 | import java.util.concurrent.locks.Lock; |
19 | import java.util.concurrent.locks.ReentrantLock; | |
53b235e1 MK |
20 | |
21 | /** | |
6a0ec7bc AM |
22 | * A CTF trace iterator manager. |
23 | * | |
24 | * Each instance of {@link CtfTmfTrace} should possess one of these, which will | |
25 | * manage the iterators that are opened to read that trace. This will allow | |
26 | * controlling the number of opened file handles per trace. | |
53b235e1 MK |
27 | * |
28 | * @author Matthew Khouzam | |
29 | */ | |
6a0ec7bc | 30 | public class CtfIteratorManager { |
53b235e1 MK |
31 | /* |
32 | * Cache size. Under 1023 on linux32 systems. Number of file handles | |
33 | * created. | |
34 | */ | |
35 | private final static int MAX_SIZE = 100; | |
6a0ec7bc AM |
36 | |
37 | /** The map of the cache */ | |
81a2d02e | 38 | private final HashMap<CtfTmfContext, CtfIterator> fMap; |
6a0ec7bc AM |
39 | |
40 | /** An array pointing to the same cache. this allows fast "random" accesses */ | |
81a2d02e | 41 | private final ArrayList<CtfTmfContext> fRandomAccess; |
6a0ec7bc AM |
42 | |
43 | /** Lock for when we access the two previous data structures */ | |
44 | private final Lock fAccessLock = new ReentrantLock(); | |
45 | ||
46 | /** The parent trace */ | |
53b235e1 | 47 | private final CtfTmfTrace fTrace; |
6a0ec7bc AM |
48 | |
49 | /** Random number generator */ | |
53b235e1 MK |
50 | private final Random fRnd; |
51 | ||
6a0ec7bc AM |
52 | /** |
53 | * Constructor | |
54 | * | |
55 | * @param trace | |
56 | * The trace whose iterators this manager will manage | |
57 | */ | |
e471302a | 58 | public CtfIteratorManager(CtfTmfTrace trace) { |
a4524c1b AM |
59 | fMap = new HashMap<>(); |
60 | fRandomAccess = new ArrayList<>(); | |
53b235e1 MK |
61 | fRnd = new Random(System.nanoTime()); |
62 | fTrace = trace; | |
63 | } | |
64 | ||
65 | /** | |
66 | * This needs explaining: the iterator table is effectively a cache. | |
67 | * Originally the contexts had a 1 to 1 structure with the file handles of a | |
68 | * trace. This failed since there is a limit to how many file handles we can | |
69 | * have opened simultaneously. Then a round-robin scheme was implemented, | |
70 | * this lead up to a two competing contexts syncing up and using the same | |
71 | * file handler, causing horrible slowdowns. Now a random replacement | |
72 | * algorithm is selected. This is the same as used by arm processors, and it | |
73 | * works quite well when many cores so this looks promising for very | |
74 | * multi-threaded systems. | |
75 | * | |
76 | * @param context | |
77 | * the context to look up | |
ecb12461 | 78 | * @return the iterator referring to the context |
53b235e1 | 79 | */ |
81a2d02e | 80 | public CtfIterator getIterator(final CtfTmfContext context) { |
53b235e1 MK |
81 | /* |
82 | * if the element is in the map, we don't need to do anything else. | |
83 | */ | |
6a0ec7bc AM |
84 | CtfIterator iter = fMap.get(context); |
85 | if (iter == null) { | |
53b235e1 | 86 | |
6a0ec7bc AM |
87 | fAccessLock.lock(); |
88 | try { | |
53b235e1 | 89 | /* |
6a0ec7bc | 90 | * Assign an iterator to a context. |
53b235e1 | 91 | */ |
6a0ec7bc AM |
92 | if (fRandomAccess.size() < MAX_SIZE) { |
93 | /* | |
94 | * if we're not full yet, just add an element. | |
95 | */ | |
96 | iter = fTrace.createIterator(); | |
97 | addElement(context, iter); | |
98 | ||
99 | } else { | |
100 | /* | |
101 | * if we're full, randomly replace an element | |
102 | */ | |
103 | iter = replaceRandomElement(context); | |
104 | } | |
105 | if (context.getLocation() != null) { | |
106 | final CtfLocationInfo location = (CtfLocationInfo) context.getLocation().getLocationInfo(); | |
107 | iter.seek(location); | |
108 | } | |
109 | } finally { | |
110 | fAccessLock.unlock(); | |
575beffc | 111 | } |
53b235e1 | 112 | } |
6a0ec7bc | 113 | return iter; |
53b235e1 MK |
114 | } |
115 | ||
6a0ec7bc AM |
116 | /** |
117 | * Remove an iterator from this manager | |
118 | * | |
119 | * @param context | |
120 | * The context of the iterator to remove | |
121 | */ | |
f0414df8 | 122 | public void removeIterator(CtfTmfContext context) { |
6a0ec7bc AM |
123 | fAccessLock.lock(); |
124 | try { | |
125 | /* The try below is only to auto-call CtfIterator.close() */ | |
126 | try (CtfIterator removed = fMap.remove(context)) { | |
127 | } | |
128 | fRandomAccess.remove(context); | |
259c81f0 | 129 | |
6a0ec7bc AM |
130 | } finally { |
131 | fAccessLock.unlock(); | |
132 | } | |
f0414df8 SD |
133 | } |
134 | ||
53b235e1 MK |
135 | /** |
136 | * Add a pair of context and element to the hashmap and the arraylist. | |
137 | * | |
138 | * @param context | |
139 | * the context | |
140 | * @param elem | |
141 | * the iterator | |
142 | */ | |
81a2d02e | 143 | private void addElement(final CtfTmfContext context, |
53b235e1 | 144 | final CtfIterator elem) { |
6a0ec7bc AM |
145 | fAccessLock.lock(); |
146 | try { | |
147 | fMap.put(context, elem); | |
148 | fRandomAccess.add(context); | |
149 | ||
150 | } finally { | |
151 | fAccessLock.unlock(); | |
152 | } | |
53b235e1 MK |
153 | } |
154 | ||
155 | /** | |
156 | * Replace a random element | |
157 | * | |
158 | * @param context | |
159 | * the context to swap in | |
160 | * @return the iterator of the removed elements. | |
161 | */ | |
6a0ec7bc | 162 | private CtfIterator replaceRandomElement(final CtfTmfContext context) { |
53b235e1 MK |
163 | /* |
164 | * This needs some explanation too: We need to select a random victim | |
165 | * and remove it. The order of the elements is not important, so instead | |
166 | * of just calling arraylist.remove(element) which has an O(n) | |
167 | * complexity, we pick an random number. The element is swapped out of | |
168 | * the array and removed and replaced in the hashmap. | |
169 | */ | |
6a0ec7bc AM |
170 | fAccessLock.lock(); // just in case, should only be called when already locked |
171 | try { | |
172 | final int size = fRandomAccess.size(); | |
173 | final int pos = fRnd.nextInt(size); | |
174 | final CtfTmfContext victim = fRandomAccess.get(pos); | |
175 | fRandomAccess.set(pos, context); | |
176 | final CtfIterator elem = fMap.remove(victim); | |
177 | fMap.put(context, elem); | |
178 | victim.dispose(); | |
179 | return elem; | |
180 | ||
181 | } finally { | |
182 | fAccessLock.unlock(); | |
183 | } | |
53b235e1 MK |
184 | } |
185 | ||
6a0ec7bc AM |
186 | /** |
187 | * Dispose this iterator manager, which will close all the remaining | |
188 | * iterators. | |
189 | */ | |
190 | public void dispose() { | |
191 | fAccessLock.lock(); | |
192 | try { | |
193 | for (CtfIterator iterator : fMap.values()) { | |
194 | iterator.dispose(); | |
195 | } | |
196 | fMap.clear(); | |
197 | fRandomAccess.clear(); | |
198 | ||
199 | } finally { | |
200 | fAccessLock.unlock(); | |
5d1c6919 | 201 | } |
5d1c6919 | 202 | } |
e471302a | 203 | } |