120 lines
4.1 KiB
C++
120 lines
4.1 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/memory/discardable_memory.h"
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#include "base/feature_list.h"
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#include "base/memory/discardable_memory_internal.h"
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#include "base/memory/madv_free_discardable_memory_posix.h"
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#include "base/metrics/field_trial_params.h"
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#include "build/build_config.h"
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#if defined(OS_ANDROID)
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#include <third_party/ashmem/ashmem.h>
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#endif // defined(OS_ANDROID)
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namespace base {
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namespace features {
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#if defined(OS_POSIX)
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// Feature flag allowing the use of MADV_FREE discardable memory when there are
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// multiple supported discardable memory backings.
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const base::Feature kMadvFreeDiscardableMemory{
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"MadvFreeDiscardableMemory", base::FEATURE_DISABLED_BY_DEFAULT};
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#endif // defined(OS_POSIX)
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#if defined(OS_ANDROID) || defined(OS_LINUX)
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const base::Feature kDiscardableMemoryBackingTrial{
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"DiscardableMemoryBackingTrial", base::FEATURE_DISABLED_BY_DEFAULT};
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// Association of trial group names to trial group enum. Array order must match
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// order of DiscardableMemoryTrialGroup enum.
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const base::FeatureParam<DiscardableMemoryTrialGroup>::Option
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kDiscardableMemoryBackingParamOptions[] = {
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{DiscardableMemoryTrialGroup::kEmulatedSharedMemory, "shmem"},
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{DiscardableMemoryTrialGroup::kMadvFree, "madvfree"},
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{DiscardableMemoryTrialGroup::kAshmem, "ashmem"}};
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const base::FeatureParam<DiscardableMemoryTrialGroup>
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kDiscardableMemoryBackingParam{
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&kDiscardableMemoryBackingTrial, "DiscardableMemoryBacking",
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DiscardableMemoryTrialGroup::kEmulatedSharedMemory,
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&kDiscardableMemoryBackingParamOptions};
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#endif // defined(OS_ANDROID) || defined(OS_LINUX)
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} // namespace features
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namespace {
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#if defined(OS_ANDROID) || defined(OS_LINUX)
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DiscardableMemoryBacking GetBackingForFieldTrial() {
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DiscardableMemoryTrialGroup trial_group =
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GetDiscardableMemoryBackingFieldTrialGroup();
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switch (trial_group) {
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case DiscardableMemoryTrialGroup::kEmulatedSharedMemory:
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case DiscardableMemoryTrialGroup::kAshmem:
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return DiscardableMemoryBacking::kSharedMemory;
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case DiscardableMemoryTrialGroup::kMadvFree:
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return DiscardableMemoryBacking::kMadvFree;
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}
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NOTREACHED();
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}
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#endif // defined(OS_ANDROID) || defined(OS_LINUX)
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} // namespace
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#if defined(OS_ANDROID) || defined(OS_LINUX)
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// Probe capabilities of this device to determine whether we should participate
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// in the discardable memory backing trial.
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bool DiscardableMemoryBackingFieldTrialIsEnabled() {
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#if defined(OS_ANDROID)
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if (!ashmem_device_is_supported())
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return false;
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#endif // defined(OS_ANDROID)
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if (base::GetMadvFreeSupport() != base::MadvFreeSupport::kSupported)
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return false;
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// IMPORTANT: Only query the feature after we determine the device has the
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// capabilities required, which will have the side-effect of assigning a
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// trial-group.
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return base::FeatureList::IsEnabled(features::kDiscardableMemoryBackingTrial);
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}
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DiscardableMemoryTrialGroup GetDiscardableMemoryBackingFieldTrialGroup() {
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DCHECK(DiscardableMemoryBackingFieldTrialIsEnabled());
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return features::kDiscardableMemoryBackingParam.Get();
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}
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#endif // defined(OS_ANDROID) || defined(OS_LINUX)
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DiscardableMemory::DiscardableMemory() = default;
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DiscardableMemory::~DiscardableMemory() = default;
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DiscardableMemoryBacking GetDiscardableMemoryBacking() {
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#if defined(OS_ANDROID) || defined(OS_LINUX)
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if (DiscardableMemoryBackingFieldTrialIsEnabled()) {
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return GetBackingForFieldTrial();
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}
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#endif // defined(OS_ANDROID) || defined(OS_LINUX)
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#if defined(OS_ANDROID)
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if (ashmem_device_is_supported())
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return DiscardableMemoryBacking::kSharedMemory;
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#endif // defined(OS_ANDROID)
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#if defined(OS_POSIX)
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if (base::FeatureList::IsEnabled(
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base::features::kMadvFreeDiscardableMemory) &&
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base::GetMadvFreeSupport() == base::MadvFreeSupport::kSupported) {
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return DiscardableMemoryBacking::kMadvFree;
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}
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#endif // defined(OS_POSIX)
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return DiscardableMemoryBacking::kSharedMemory;
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}
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} // namespace base
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