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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 "third_party/blink/renderer/core/timing/memory_info.h"
#include <limits>
#include "base/macros.h"
#include "base/time/default_tick_clock.h"
#include "third_party/blink/renderer/core/frame/local_frame.h"
#include "third_party/blink/renderer/core/frame/settings.h"
#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
#include "third_party/blink/renderer/platform/wtf/math_extras.h"
#include "third_party/blink/renderer/platform/wtf/thread_specific.h"
#include "v8/include/v8.h"
namespace blink {
static constexpr base::TimeDelta kTwentyMinutes =
base::TimeDelta::FromMinutes(20);
static constexpr base::TimeDelta kFiftyMs =
base::TimeDelta::FromMilliseconds(50);
static void GetHeapSize(HeapInfo& info) {
v8::HeapStatistics heap_statistics;
v8::Isolate::GetCurrent()->GetHeapStatistics(&heap_statistics);
info.used_js_heap_size =
heap_statistics.used_heap_size() + heap_statistics.external_memory();
info.total_js_heap_size =
heap_statistics.total_physical_size() + heap_statistics.external_memory();
info.js_heap_size_limit = heap_statistics.heap_size_limit();
}
class HeapSizeCache {
USING_FAST_MALLOC(HeapSizeCache);
public:
HeapSizeCache() : clock_(base::DefaultTickClock::GetInstance()) {}
void GetCachedHeapSize(HeapInfo& info, MemoryInfo::Precision precision) {
MaybeUpdate(precision);
info = info_;
}
static HeapSizeCache& ForCurrentThread() {
DEFINE_THREAD_SAFE_STATIC_LOCAL(ThreadSpecific<HeapSizeCache>,
heap_size_cache, ());
return *heap_size_cache;
}
void SetTickClockForTesting(const base::TickClock* clock) { clock_ = clock; }
void ResetLastUpdateTimeForTesting() { last_update_time_ = base::nullopt; }
private:
void MaybeUpdate(MemoryInfo::Precision precision) {
// We rate-limit queries to once every twenty minutes in the Bucketized case
// to make it more difficult for attackers to compare memory usage before
// and after some event. We limit to once every 50 ms in the Precise case to
// avoid exposing precise GC timings.
base::TimeTicks now = clock_->NowTicks();
base::TimeDelta delta_allowed =
precision == MemoryInfo::Precision::Bucketized ? kTwentyMinutes
: kFiftyMs;
if (!last_update_time_.has_value() ||
now - last_update_time_.value() >= delta_allowed) {
Update(precision);
last_update_time_ = now;
}
}
void Update(MemoryInfo::Precision precision) {
GetHeapSize(info_);
if (precision == MemoryInfo::Precision::Precise)
return;
info_.used_js_heap_size = QuantizeMemorySize(info_.used_js_heap_size);
info_.total_js_heap_size = QuantizeMemorySize(info_.total_js_heap_size);
info_.js_heap_size_limit = QuantizeMemorySize(info_.js_heap_size_limit);
}
base::Optional<base::TimeTicks> last_update_time_;
const base::TickClock* clock_;
HeapInfo info_;
DISALLOW_COPY_AND_ASSIGN(HeapSizeCache);
};
// 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 kNumberOfBuckets = 100;
DEFINE_STATIC_LOCAL(Vector<size_t>, bucket_size_list, ());
if (bucket_size_list.IsEmpty()) {
bucket_size_list.resize(kNumberOfBuckets);
float size_of_next_bucket =
10000000.0; // First bucket size is roughly 10M.
const float kLargestBucketSize = 4000000000.0; // Roughly 4GB.
// We scale with the Nth root of the ratio, so that we use all the bucktes.
const float scaling_factor =
exp(log(kLargestBucketSize / size_of_next_bucket) / kNumberOfBuckets);
size_t next_power_of_ten = static_cast<size_t>(
pow(10, floor(log10(size_of_next_bucket)) + 1) + 0.5);
size_t granularity =
next_power_of_ten / 1000; // We want 3 signficant digits.
for (int i = 0; i < kNumberOfBuckets; ++i) {
size_t current_bucket_size = static_cast<size_t>(size_of_next_bucket);
bucket_size_list[i] =
current_bucket_size - (current_bucket_size % granularity);
size_of_next_bucket *= scaling_factor;
if (size_of_next_bucket >= next_power_of_ten) {
if (std::numeric_limits<size_t>::max() / 10 <= next_power_of_ten) {
next_power_of_ten = std::numeric_limits<size_t>::max();
} else {
next_power_of_ten *= 10;
granularity *= 10;
}
}
// Watch out for overflow, if the range is too large for size_t.
if (i > 0 && bucket_size_list[i] < bucket_size_list[i - 1])
bucket_size_list[i] = std::numeric_limits<size_t>::max();
}
}
for (int i = 0; i < kNumberOfBuckets; ++i) {
if (size <= bucket_size_list[i])
return bucket_size_list[i];
}
return bucket_size_list[kNumberOfBuckets - 1];
}
MemoryInfo::MemoryInfo(Precision precision) {
// With the experimental PreciseMemoryInfoEnabled flag on, we will not
// bucketize or cache values, regardless of the value of |precision|. When the
// flag is off then our cache is used and |precision| determines the
// granularity of the values and the timer of the cache we use.
if (RuntimeEnabledFeatures::PreciseMemoryInfoEnabled())
GetHeapSize(info_);
else
HeapSizeCache::ForCurrentThread().GetCachedHeapSize(info_, precision);
// The values must have been computed, so totalJSHeapSize must be greater than
// 0.
DCHECK_GT(totalJSHeapSize(), 0u);
}
// static
void MemoryInfo::SetTickClockForTestingForCurrentThread(
const base::TickClock* clock) {
HeapSizeCache& cache = HeapSizeCache::ForCurrentThread();
cache.SetTickClockForTesting(clock);
cache.ResetLastUpdateTimeForTesting();
}
} // namespace blink
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