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/*
* Copyright (C) 2010 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "core/timing/MemoryInfo.h"
#include <limits>
#include "core/frame/Frame.h"
#include "core/frame/Settings.h"
#include "wtf/CurrentTime.h"
#include "wtf/MainThread.h"
#include "wtf/MathExtras.h"
namespace WebCore {
class HeapSizeCache {
WTF_MAKE_NONCOPYABLE(HeapSizeCache); WTF_MAKE_FAST_ALLOCATED;
public:
HeapSizeCache()
: m_lastUpdateTime(0)
{
}
void getCachedHeapSize(HeapInfo& info)
{
maybeUpdate();
info = m_info;
}
private:
void maybeUpdate()
{
// We rate-limit queries to once every twenty minutes to make it more difficult
// for attackers to compare memory usage before and after some event.
const double TwentyMinutesInSeconds = 20 * 60;
double now = monotonicallyIncreasingTime();
if (now - m_lastUpdateTime >= TwentyMinutesInSeconds) {
update();
m_lastUpdateTime = now;
}
}
void update()
{
ScriptGCEvent::getHeapSize(m_info);
m_info.usedJSHeapSize = quantizeMemorySize(m_info.usedJSHeapSize);
m_info.totalJSHeapSize = quantizeMemorySize(m_info.totalJSHeapSize);
m_info.jsHeapSizeLimit = quantizeMemorySize(m_info.jsHeapSizeLimit);
}
double m_lastUpdateTime;
HeapInfo m_info;
};
// We quantize the sizes to make it more difficult for an attacker to see precise
// impact of operations on memory. The values are used for performance tuning,
// and hence don't need to be as refined when the value is large, so we threshold
// at a list of exponentially separated buckets.
size_t quantizeMemorySize(size_t size)
{
const int numberOfBuckets = 100;
DEFINE_STATIC_LOCAL(Vector<size_t>, bucketSizeList, ());
ASSERT(isMainThread());
if (bucketSizeList.isEmpty()) {
bucketSizeList.resize(numberOfBuckets);
float sizeOfNextBucket = 10000000.0; // First bucket size is roughly 10M.
const float largestBucketSize = 4000000000.0; // Roughly 4GB.
// We scale with the Nth root of the ratio, so that we use all the bucktes.
const float scalingFactor = exp(log(largestBucketSize / sizeOfNextBucket) / numberOfBuckets);
size_t nextPowerOfTen = static_cast<size_t>(pow(10, floor(log10(sizeOfNextBucket)) + 1) + 0.5);
size_t granularity = nextPowerOfTen / 1000; // We want 3 signficant digits.
for (int i = 0; i < numberOfBuckets; ++i) {
size_t currentBucketSize = static_cast<size_t>(sizeOfNextBucket);
bucketSizeList[i] = currentBucketSize - (currentBucketSize % granularity);
sizeOfNextBucket *= scalingFactor;
if (sizeOfNextBucket >= nextPowerOfTen) {
if (std::numeric_limits<size_t>::max() / 10 <= nextPowerOfTen) {
nextPowerOfTen = std::numeric_limits<size_t>::max();
} else {
nextPowerOfTen *= 10;
granularity *= 10;
}
}
// Watch out for overflow, if the range is too large for size_t.
if (i > 0 && bucketSizeList[i] < bucketSizeList[i - 1])
bucketSizeList[i] = std::numeric_limits<size_t>::max();
}
}
for (int i = 0; i < numberOfBuckets; ++i) {
if (size <= bucketSizeList[i])
return bucketSizeList[i];
}
return bucketSizeList[numberOfBuckets - 1];
}
MemoryInfo::MemoryInfo(Frame* frame)
{
ScriptWrappable::init(this);
if (!frame || !frame->settings())
return;
if (frame->settings()->memoryInfoEnabled()) {
ScriptGCEvent::getHeapSize(m_info);
} else {
DEFINE_STATIC_LOCAL(HeapSizeCache, heapSizeCache, ());
heapSizeCache.getCachedHeapSize(m_info);
}
}
} // namespace WebCore
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