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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/performance_manager/public/dll_pre_read_policy_win.h"
#include <atomic>
#include <optional>
#include "base/base_paths.h"
#include "base/feature_list.h"
#include "base/files/drive_info.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/functional/bind.h"
#include "base/metrics/field_trial_params.h"
#include "base/path_service.h"
#include "base/task/thread_pool.h"
#include "base/time/time.h"
#include "chrome/browser/browser_features.h"
#include "components/startup_metric_utils/common/startup_metric_utils.h"
namespace performance_manager {
namespace {
enum class ChromeDllOnSsd {
// It is as of yet unknown whether the Chrome DLL is on an SSD.
kPending,
// It can positively be determined that the Chrome DLL is on a non-removable
// SSD.
kOnFixedSsd,
// Either the Chrome DLL is on a spinning disk, a removable SSD, or whether
// its drive is an SSD/is removable was unable to be determined.
kNotOnFixedSsd,
};
// Seek penalty state. All reads/writes use std::memory_order_relaxed because
// there is no dependency between those and other memory operations.
std::atomic<ChromeDllOnSsd> g_chrome_dll_on_ssd = ChromeDllOnSsd::kPending;
} // namespace
// Returns true if `drive_info` indicates a disk that has no seek penalty, is
// not removable, and is not connected via a USB bus. In other words, has the
// highest liklihood of exceedingly fast performance.
bool IsFixedSsd(const std::optional<base::DriveInfo>& drive_info) {
return drive_info.has_value() &&
!drive_info->has_seek_penalty.value_or(true) &&
!drive_info->is_removable.value_or(true) &&
!drive_info->is_usb.value_or(true);
}
void SetChromeDllOnSsdForTesting(bool on_fixed_ssd) {
g_chrome_dll_on_ssd.store(on_fixed_ssd ? ChromeDllOnSsd::kOnFixedSsd
: ChromeDllOnSsd::kNotOnFixedSsd);
}
void InitializeDllPrereadPolicy() {
CHECK_EQ(g_chrome_dll_on_ssd.load(std::memory_order_relaxed),
ChromeDllOnSsd::kPending);
// This function uses atomics to coordinate whether the Chrome DLL is on a
// fixed SSD because the query races with child process creation, and the
// value would like to be known on the main thread as soon as possible.
base::ThreadPool::PostTask(
FROM_HERE,
{base::MayBlock(), base::TaskPriority::USER_VISIBLE,
base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
base::BindOnce([]() {
base::FilePath current_module_path;
std::optional<base::DriveInfo> drive_info;
if (base::PathService::Get(base::FILE_MODULE, ¤t_module_path)) {
drive_info = base::GetFileDriveInfo(current_module_path);
}
g_chrome_dll_on_ssd.store(IsFixedSsd(drive_info)
? ChromeDllOnSsd::kOnFixedSsd
: ChromeDllOnSsd::kNotOnFixedSsd);
}));
}
bool StartupPrefetchTimeoutElapsed(base::TimeTicks now) {
return (now - startup_metric_utils::GetCommon().MainEntryPointTicks()) >
features::kNoPreReadMainDllStartup_StartupDuration.Get();
}
bool ShouldPreReadDllInChild() {
if (base::FeatureList::IsEnabled(features::kNoPreReadMainDll)) {
return false;
}
// If it hasn't been determined yet whether the Chrome binary has a seek
// penalty, don't pre-read. In that state, the browser process has
// likely pre-read the DLL recently and pre-reading again is likely not
// needed, even if there is a seek penalty.
if (g_chrome_dll_on_ssd.load(std::memory_order_relaxed) !=
ChromeDllOnSsd::kNotOnFixedSsd &&
base::FeatureList::IsEnabled(features::kNoPreReadMainDllIfSsd)) {
return false;
}
// `NoPreReadMainDllStartup` may only select a group for users which are not
// in `NoPreReadMainDll` AND (have a seek penalty OR are not in
// `NoPreReadMainDllIfSsd`).
if (base::FeatureList::IsEnabled(features::kNoPreReadMainDllStartup) &&
!StartupPrefetchTimeoutElapsed(base::TimeTicks::Now())) {
return false;
}
// TODO(crbug.com/331612431): Add a feature which skips pre-read if one was
// completed recently.
return true;
}
} // namespace performance_manager
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