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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