Split initialization_util into a Hermetic Library and a Variations Library

components/task_scheduler_util/variations/browser_variations_util.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/task_scheduler_util/variations/browser_variations_util.h"
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_split.h"
+#include "base/task_scheduler/initialization_util.h"
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
+#include "base/task_scheduler/switches.h"
+#include "base/task_scheduler/task_traits.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "base/time/time.h"
+#include "build/build_config.h"
+#include "components/task_scheduler_util/initialization/browser_util.h"
+#include "components/variations/variations_associated_data.h"
+
+namespace task_scheduler_util {
+namespace variations {
+
+namespace {
+
+constexpr char kFieldTrialName[] = "BrowserScheduler";
+
+// Converts |pool_descriptor| to a SingleWorkerPoolConfiguration. Returns a
+// default SingleWorkerPoolConfiguration on failure.
+//
+// |pool_descriptor| is a semi-colon separated value string with the following
+// items:
+// 0. Minimum Thread Count (int)
+// 1. Maximum Thread Count (int)
+// 2. Thread Count Multiplier (double)
+// 3. Thread Count Offset (int)
+// 4. Detach Time in Milliseconds (milliseconds)
+// 5. Standby Thread Policy (string)
+// Additional values may appear as necessary and will be ignored.
+initialization::SingleWorkerPoolConfiguration
+StringToSingleWorkerPoolConfiguration(const base::StringPiece pool_descriptor) {
+  using StandbyThreadPolicy =
+      base::SchedulerWorkerPoolParams::StandbyThreadPolicy;
+  const std::vector<base::StringPiece> tokens = SplitStringPiece(
+      pool_descriptor, ";", base::KEEP_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
+  // The below call would normally be inline, but some compilers (like MSVC)
+  // will warn that the number declarations below are uninitialized. Putting the
+  // as_string() call immediately above the declarations works around that.

[gab, 2016/12/07 20:17:22]

Hmm that seems incorrect to me, i.e. say we fix StringToDouble to use
StringPiece then this goes away and causes unrelated issues below...

Just initialize the numbers to zero at decl-site and inline as_string()

[robliao, 2016/12/07 21:55:37]

Initialized to 0 + added a comment. Changing StringToDouble to handle
StringPieces has some subtleties that this doesn't need to wait on.

+  const std::string tokens_2_str = tokens[2].as_string();
+  int min;
+  int max;
+  double cores_multiplier;
+  int offset;
+  int detach_milliseconds;
+  // Checking for a size greater than the expected amount allows us to be
+  // forward compatible if we add more variation values.
+  if (tokens.size() >= 5 && base::StringToInt(tokens[0], &min) &&
+      base::StringToInt(tokens[1], &max) &&
+      base::StringToDouble(tokens_2_str, &cores_multiplier) &&
+      base::StringToInt(tokens[3], &offset) &&
+      base::StringToInt(tokens[4], &detach_milliseconds)) {
+    initialization::SingleWorkerPoolConfiguration config;
+    config.threads = base::RecommendedMaxNumberOfThreadsInPool(
+        min, max, cores_multiplier, offset);
+    config.detach_period =
+        base::TimeDelta::FromMilliseconds(detach_milliseconds);
+    config.standby_thread_policy = (tokens.size() >= 6 && tokens[5] == "lazy")
+                                       ? StandbyThreadPolicy::LAZY
+                                       : StandbyThreadPolicy::ONE;
+    return config;
+  }
+  DLOG(ERROR) << "Invalid Worker Pool Descriptor: " << pool_descriptor;
+  return initialization::SingleWorkerPoolConfiguration();
+}
+
+// Converts a browser-based |variation_params| to
+// std::vector<base::SchedulerWorkerPoolParams>. Returns an empty vector on
+// failure.
+std::vector<base::SchedulerWorkerPoolParams>
+VariationsParamsToSchedulerWorkerPoolParamsVector(
+    const std::map<std::string, std::string>& variation_params) {
+  static const char* const kWorkerPoolNames[] = {
+      "Background", "BackgroundFileIO", "Foreground", "ForegroundFileIO"};
+  static_assert(
+      arraysize(kWorkerPoolNames) == initialization::WORKER_POOL_COUNT,
+      "Mismatched Worker Pool Types and Worker Pool Names");
+  initialization::BrowserWorkerPoolsConfiguration config;
+  initialization::SingleWorkerPoolConfiguration* const all_pools[]{
+      &config.background, &config.background_file_io, &config.foreground,
+      &config.foreground_file_io,
+  };
+  static_assert(arraysize(kWorkerPoolNames) == arraysize(all_pools),
+                "Mismatched Worker Pool Names and All Pools Array");
+  for (size_t i = 0; i < arraysize(kWorkerPoolNames); ++i) {
+    const auto* const worker_pool_name = kWorkerPoolNames[i];
+    const auto pair = variation_params.find(worker_pool_name);
+    if (pair == variation_params.end()) {
+      DLOG(ERROR) << "Missing Worker Pool Configuration: " << worker_pool_name;
+      return std::vector<base::SchedulerWorkerPoolParams>();
+    }
+
+    auto* const pool_config = all_pools[i];
+    *pool_config = StringToSingleWorkerPoolConfiguration(pair->second);
+    if (pool_config->threads <= 0 ||
+        pool_config->detach_period <= base::TimeDelta()) {
+      DLOG(ERROR) << "Invalid Worker Pool Configuration: " << worker_pool_name
+                  << " [" << pair->second << "]";
+      return std::vector<base::SchedulerWorkerPoolParams>();
+    }
+  }
+  return BrowserWorkerPoolConfigurationToSchedulerWorkerPoolParams(config);
+}
+
+}  // namespace
+
+std::vector<base::SchedulerWorkerPoolParams>
+GetBrowserSchedulerWorkerPoolParamsFromVariations() {
+  std::map<std::string, std::string> variation_params;
+  if (!::variations::GetVariationParams(kFieldTrialName, &variation_params))
+    return std::vector<base::SchedulerWorkerPoolParams>();
+
+  return VariationsParamsToSchedulerWorkerPoolParamsVector(variation_params);
+}
+
+void MaybePerformBrowserTaskSchedulerRedirection() {
+  std::map<std::string, std::string> variation_params;
+  ::variations::GetVariationParams(kFieldTrialName, &variation_params);
+
+  // TODO(gab): Remove this when http://crbug.com/622400 concludes.
+  const auto sequenced_worker_pool_param =
+      variation_params.find("RedirectSequencedWorkerPools");
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableBrowserTaskScheduler) &&
+      sequenced_worker_pool_param != variation_params.end() &&
+      sequenced_worker_pool_param->second == "true") {
+    base::SequencedWorkerPool::EnableWithRedirectionToTaskSchedulerForProcess();
+  } else {
+    base::SequencedWorkerPool::EnableForProcess();
+  }
+}
+
+}  // variations
+}  // namespace task_scheduler_util