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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:
     47     HeapSizeCache()
     48         : m_lastUpdateTime(0)
     49     {
     50     }
     51 
     52     void getCachedHeapSize(HeapInfo& info)
     53     {
     54         maybeUpdate();
     55         info = m_info;
     56     }
     57 
     58 private:
     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 
     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.
     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 
    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