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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/memory/discardable_memory.h"
#include "base/feature_list.h"
#include "base/memory/discardable_memory_internal.h"
#include "base/memory/madv_free_discardable_memory_posix.h"
#include "base/metrics/field_trial_params.h"
#include "base/notreached.h"
#include "build/build_config.h"
#if BUILDFLAG(IS_ANDROID)
#include "third_party/ashmem/ashmem.h"
#endif // BUILDFLAG(IS_ANDROID)
namespace base {
namespace features {
#if BUILDFLAG(IS_POSIX)
// Feature flag allowing the use of MADV_FREE discardable memory when there are
// multiple supported discardable memory backings.
BASE_FEATURE(kMadvFreeDiscardableMemory,
"MadvFreeDiscardableMemory",
base::FEATURE_DISABLED_BY_DEFAULT);
#endif // BUILDFLAG(IS_POSIX)
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
BASE_FEATURE(kDiscardableMemoryBackingTrial,
"DiscardableMemoryBackingTrial",
base::FEATURE_DISABLED_BY_DEFAULT);
BASE_FEATURE_ENUM_PARAM(DiscardableMemoryTrialGroup,
kDiscardableMemoryBackingParam,
&kDiscardableMemoryBackingTrial,
"DiscardableMemoryBacking",
DiscardableMemoryTrialGroup::kEmulatedSharedMemory,
kDiscardableMemoryBackingParamOptions);
#endif // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) ||
// BUILDFLAG(IS_CHROMEOS)
} // namespace features
namespace {
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
DiscardableMemoryBacking GetBackingForFieldTrial() {
DiscardableMemoryTrialGroup trial_group =
GetDiscardableMemoryBackingFieldTrialGroup();
switch (trial_group) {
case DiscardableMemoryTrialGroup::kEmulatedSharedMemory:
case DiscardableMemoryTrialGroup::kAshmem:
return DiscardableMemoryBacking::kSharedMemory;
case DiscardableMemoryTrialGroup::kMadvFree:
return DiscardableMemoryBacking::kMadvFree;
}
NOTREACHED();
}
#endif // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) ||
// BUILDFLAG(IS_CHROMEOS)
} // namespace
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
// Probe capabilities of this device to determine whether we should participate
// in the discardable memory backing trial.
bool DiscardableMemoryBackingFieldTrialIsEnabled() {
#if BUILDFLAG(IS_ANDROID)
if (!ashmem_device_is_supported()) {
return false;
}
#endif // BUILDFLAG(IS_ANDROID)
if (base::GetMadvFreeSupport() != base::MadvFreeSupport::kSupported) {
return false;
}
// IMPORTANT: Only query the feature after we determine the device has the
// capabilities required, which will have the side-effect of assigning a
// trial-group.
return base::FeatureList::IsEnabled(features::kDiscardableMemoryBackingTrial);
}
DiscardableMemoryTrialGroup GetDiscardableMemoryBackingFieldTrialGroup() {
DCHECK(DiscardableMemoryBackingFieldTrialIsEnabled());
return features::kDiscardableMemoryBackingParam.Get();
}
#endif // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) ||
// BUILDFLAG(IS_CHROMEOS)
DiscardableMemory::DiscardableMemory() = default;
DiscardableMemory::~DiscardableMemory() = default;
DiscardableMemoryBacking GetDiscardableMemoryBacking() {
#if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
if (DiscardableMemoryBackingFieldTrialIsEnabled()) {
return GetBackingForFieldTrial();
}
#endif // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) ||
// BUILDFLAG(IS_CHROMEOS)
#if BUILDFLAG(IS_ANDROID)
if (ashmem_device_is_supported()) {
return DiscardableMemoryBacking::kSharedMemory;
}
#endif // BUILDFLAG(IS_ANDROID)
#if BUILDFLAG(IS_POSIX)
if (base::FeatureList::IsEnabled(
base::features::kMadvFreeDiscardableMemory) &&
base::GetMadvFreeSupport() == base::MadvFreeSupport::kSupported) {
return DiscardableMemoryBacking::kMadvFree;
}
#endif // BUILDFLAG(IS_POSIX)
return DiscardableMemoryBacking::kSharedMemory;
}
} // namespace base
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