Re-land: content: Use NumberOfProcessors() / 2 raster threads.

content/browser/gpu/compositor_util.cc

 // Copyright (c) 2012 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 "content/browser/gpu/compositor_util.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/sys_info.h"
 #include "build/build_config.h"
+#include "cc/base/math_util.h"
 #include "cc/base/switches.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "content/public/common/content_switches.h"
 #include "gpu/config/gpu_feature_type.h"
 
 namespace content {
 
 namespace {
 
 static bool IsGpuRasterizationBlacklisted() {
   GpuDataManagerImpl* manager = GpuDataManagerImpl::GetInstance();
   return manager->IsFeatureBlacklisted(
         gpu::GPU_FEATURE_TYPE_GPU_RASTERIZATION);
 }
 
 const char* kGpuCompositingFeatureName = "gpu_compositing";
 const char* kWebGLFeatureName = "webgl";
 const char* kRasterizationFeatureName = "rasterization";
 const char* kThreadedRasterizationFeatureName = "threaded_rasterization";
 const char* kMultipleRasterThreadsFeatureName = "multiple_raster_threads";
 
 const int kMinRasterThreads = 1;
-const int kMaxRasterThreads = 64;
+const int kMaxRasterThreads = 16;
 
 const int kMinMSAASampleCount = 0;
 
 struct GpuFeatureInfo {
   std::string name;
   bool blocked;
   bool disabled;
   std::string disabled_description;
   bool fallback_to_software;
 };
@@ skipping 157 matching lines @@
 
 bool IsImplSidePaintingEnabled() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kDisableImplSidePainting))
     return false;
   return true;
 }
 
 int NumberOfRendererRasterThreads() {
-  int num_raster_threads = 1;
+  int num_raster_threads = base::SysInfo::NumberOfProcessors() / 2;

[jdduke (slow), 2015/05/28 23:23:31]

What does this return on octacore big/little ARM devices? We really want it to
be "4", but I fear this returns "8".

Android has a special API to get the CPU count, and I believe it returns 4 for
such devices, but it looks like we're using the posix
"sysconf(_SC_NPROCESSORS_CONF)"... wonder if we should switch the Android
implementation for NumberOfProcessors() to use android_getCpuCount() from the
NDK.

 
-  // Async uploads uses its own thread, so allow an extra thread when async
-  // uploads is not in use.
-  bool allow_extra_thread =
-      IsZeroCopyUploadEnabled() || IsOneCopyUploadEnabled();
-  if (base::SysInfo::NumberOfProcessors() >= 4 && allow_extra_thread)
-    num_raster_threads = 2;
+  // Async uploads is used when neither zero-copy nor one-copy is enabled and
+  // it uses its own thread, so reduce the number of raster threads when async
+  // uploads is in use.
+  bool async_uploads_is_used =
+      !IsZeroCopyUploadEnabled() && !IsOneCopyUploadEnabled();
+  if (async_uploads_is_used)
+    --num_raster_threads;
 
-  int force_num_raster_threads = ForceNumberOfRendererRasterThreads();
-  if (force_num_raster_threads)
-    num_raster_threads = force_num_raster_threads;
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
 
-  return num_raster_threads;
+  if (command_line.HasSwitch(switches::kNumRasterThreads)) {
+    std::string string_value = command_line.GetSwitchValueASCII(
+        switches::kNumRasterThreads);
+    if (!base::StringToInt(string_value, &num_raster_threads)) {
+      DLOG(WARNING) << "Failed to parse switch " <<
+          switches::kNumRasterThreads  << ": " << string_value;
+    }
+  }
+
+  return cc::MathUtil::ClampToRange(num_raster_threads, kMinRasterThreads,
+                                    kMaxRasterThreads);
 }
 
 bool IsOneCopyUploadEnabled() {
   if (IsZeroCopyUploadEnabled())
     return false;
 
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kEnableOneCopy))
     return true;
   if (command_line.HasSwitch(switches::kDisableOneCopy))
     return false;
 
 #if defined(OS_ANDROID)
   return false;
 #endif
   return true;
 }
 
 bool IsZeroCopyUploadEnabled() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   return command_line.HasSwitch(switches::kEnableZeroCopy);
 }
 
-int ForceNumberOfRendererRasterThreads() {
-  const base::CommandLine& command_line =
-      *base::CommandLine::ForCurrentProcess();
-
-  if (!command_line.HasSwitch(switches::kNumRasterThreads))
-    return 0;
-  std::string string_value =
-      command_line.GetSwitchValueASCII(switches::kNumRasterThreads);
-  int force_num_raster_threads = 0;
-  if (base::StringToInt(string_value, &force_num_raster_threads) &&
-      force_num_raster_threads >= kMinRasterThreads &&
-      force_num_raster_threads <= kMaxRasterThreads) {
-    return force_num_raster_threads;
-  } else {
-    DLOG(WARNING) << "Failed to parse switch " <<
-        switches::kNumRasterThreads  << ": " << string_value;
-    return 0;
-  }
-}
-
 bool IsGpuRasterizationEnabled() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   if (!IsImplSidePaintingEnabled())
     return false;
 
   if (command_line.HasSwitch(switches::kDisableGpuRasterization))
     return false;
   else if (command_line.HasSwitch(switches::kEnableGpuRasterization))
@@ skipping 94 matching lines @@
     } else {
       status = "enabled";
       if (gpu_feature_info.name == kWebGLFeatureName &&
           manager->IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_GPU_COMPOSITING))
         status += "_readback";
       if (gpu_feature_info.name == kRasterizationFeatureName) {
         if (IsForceGpuRasterizationEnabled())
           status += "_force";
       }
       if (gpu_feature_info.name == kMultipleRasterThreadsFeatureName) {
-        if (ForceNumberOfRendererRasterThreads() > 0)
+        const base::CommandLine& command_line =
+            *base::CommandLine::ForCurrentProcess();
+        if (command_line.HasSwitch(switches::kNumRasterThreads))
           status += "_force";
       }
       if (gpu_feature_info.name == kThreadedRasterizationFeatureName ||
           gpu_feature_info.name == kMultipleRasterThreadsFeatureName)
         status += "_on";
     }
     if (gpu_feature_info.name == kWebGLFeatureName &&
         (gpu_feature_info.blocked || gpu_access_blocked) &&
         manager->ShouldUseSwiftShader()) {
       status = "unavailable_software";
@@ skipping 44 matching lines @@
     }
   }
   return problem_list;
 }
 
 std::vector<std::string> GetDriverBugWorkarounds() {
   return GpuDataManagerImpl::GetInstance()->GetDriverBugWorkarounds();
 }
 
 }  // namespace content