1 /*
2 * Copyright (C) 2010 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 * * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include "config.h"
32 #include "core/timing/MemoryInfo.h"
33
34 #include "core/frame/LocalFrame.h"
35 #include "core/frame/Settings.h"
36 #include "platform/RuntimeEnabledFeatures.h"
37 #include "wtf/CurrentTime.h"
38 #include "wtf/MainThread.h"
39 #include "wtf/MathExtras.h"
40 #include <limits>
41
42 namespace blink {
43
44 class HeapSizeCache {
45 WTF_MAKE_NONCOPYABLE(HeapSizeCache); WTF_MAKE_FAST_ALLOCATED;
46 public:
HeapSizeCache()47 HeapSizeCache()
48 : m_lastUpdateTime(0)
49 {
50 }
51
getCachedHeapSize(HeapInfo & info)52 void getCachedHeapSize(HeapInfo& info)
53 {
54 maybeUpdate();
55 info = m_info;
56 }
57
58 private:
maybeUpdate()59 void maybeUpdate()
60 {
61 // We rate-limit queries to once every twenty minutes to make it more difficult
62 // for attackers to compare memory usage before and after some event.
63 const double TwentyMinutesInSeconds = 20 * 60;
64
65 double now = monotonicallyIncreasingTime();
66 if (now - m_lastUpdateTime >= TwentyMinutesInSeconds) {
67 update();
68 m_lastUpdateTime = now;
69 }
70 }
71
update()72 void update()
73 {
74 ScriptGCEvent::getHeapSize(m_info);
75 m_info.usedJSHeapSize = quantizeMemorySize(m_info.usedJSHeapSize);
76 m_info.totalJSHeapSize = quantizeMemorySize(m_info.totalJSHeapSize);
77 m_info.jsHeapSizeLimit = quantizeMemorySize(m_info.jsHeapSizeLimit);
78 }
79
80 double m_lastUpdateTime;
81
82 HeapInfo m_info;
83 };
84
85 // We quantize the sizes to make it more difficult for an attacker to see precise
86 // impact of operations on memory. The values are used for performance tuning,
87 // and hence don't need to be as refined when the value is large, so we threshold
88 // at a list of exponentially separated buckets.
quantizeMemorySize(size_t size)89 size_t quantizeMemorySize(size_t size)
90 {
91 const int numberOfBuckets = 100;
92 DEFINE_STATIC_LOCAL(Vector<size_t>, bucketSizeList, ());
93
94 if (bucketSizeList.isEmpty()) {
95 bucketSizeList.resize(numberOfBuckets);
96
97 float sizeOfNextBucket = 10000000.0; // First bucket size is roughly 10M.
98 const float largestBucketSize = 4000000000.0; // Roughly 4GB.
99 // We scale with the Nth root of the ratio, so that we use all the bucktes.
100 const float scalingFactor = exp(log(largestBucketSize / sizeOfNextBucket) / numberOfBuckets);
101
102 size_t nextPowerOfTen = static_cast<size_t>(pow(10, floor(log10(sizeOfNextBucket)) + 1) + 0.5);
103 size_t granularity = nextPowerOfTen / 1000; // We want 3 signficant digits.
104
105 for (int i = 0; i < numberOfBuckets; ++i) {
106 size_t currentBucketSize = static_cast<size_t>(sizeOfNextBucket);
107 bucketSizeList[i] = currentBucketSize - (currentBucketSize % granularity);
108
109 sizeOfNextBucket *= scalingFactor;
110 if (sizeOfNextBucket >= nextPowerOfTen) {
111 if (std::numeric_limits<size_t>::max() / 10 <= nextPowerOfTen) {
112 nextPowerOfTen = std::numeric_limits<size_t>::max();
113 } else {
114 nextPowerOfTen *= 10;
115 granularity *= 10;
116 }
117 }
118
119 // Watch out for overflow, if the range is too large for size_t.
120 if (i > 0 && bucketSizeList[i] < bucketSizeList[i - 1])
121 bucketSizeList[i] = std::numeric_limits<size_t>::max();
122 }
123 }
124
125 for (int i = 0; i < numberOfBuckets; ++i) {
126 if (size <= bucketSizeList[i])
127 return bucketSizeList[i];
128 }
129
130 return bucketSizeList[numberOfBuckets - 1];
131 }
132
MemoryInfo()133 MemoryInfo::MemoryInfo()
134 {
135 if (RuntimeEnabledFeatures::preciseMemoryInfoEnabled()) {
136 ScriptGCEvent::getHeapSize(m_info);
137 } else {
138 DEFINE_STATIC_LOCAL(HeapSizeCache, heapSizeCache, ());
139 heapSizeCache.getCachedHeapSize(m_info);
140 }
141 }
142
143 } // namespace blink
144