Use persistent memory for receiving metrics from sub-processes.

content/browser/browser_child_process_host_impl.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/browser_child_process_host_impl.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/dump_without_crashing.h"
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/persistent_histogram_allocator.h"
+#include "base/metrics/persistent_memory_allocator.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "components/tracing/common/tracing_switches.h"
 #include "content/browser/histogram_message_filter.h"
 #include "content/browser/loader/resource_message_filter.h"
 #include "content/browser/memory/memory_message_filter.h"
@@ skipping 143 matching lines @@
 
   power_monitor_message_broadcaster_.Init();
 
   if (!service_name.empty()) {
     DCHECK_CURRENTLY_ON(BrowserThread::IO);
     child_connection_.reset(new MojoChildConnection(
         service_name, base::StringPrintf("%d", data_.id), child_token_,
         MojoShellContext::GetConnectorForIOThread(),
         base::ThreadTaskRunnerHandle::Get()));
   }
+
+  // Create a persistent memory segment for subprocess histograms.
+  CreateMetricsAllocator();
 }
 
 BrowserChildProcessHostImpl::~BrowserChildProcessHostImpl() {
   g_child_process_list.Get().remove(this);
 
   if (notify_child_disconnected_) {
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                             base::Bind(&NotifyProcessHostDisconnected, data_));
   }
 }
@@ skipping 85 matching lines @@
 
 const base::Process& BrowserChildProcessHostImpl::GetProcess() const {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(child_process_.get())
       << "Requesting a child process handle before launching.";
   DCHECK(child_process_->GetProcess().IsValid())
       << "Requesting a child process handle before launch has completed OK.";
   return child_process_->GetProcess();
 }
 
+std::unique_ptr<base::SharedPersistentMemoryAllocator>
+BrowserChildProcessHostImpl::TakeMetricsAllocator() {
+  return std::move(metrics_allocator_);
+}
+
 void BrowserChildProcessHostImpl::SetName(const base::string16& name) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   data_.name = name;
 }
 
 void BrowserChildProcessHostImpl::SetHandle(base::ProcessHandle handle) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   data_.handle = handle;
 }
 
@@ skipping 50 matching lines @@
   // error on the IPC channel.
   early_exit_watcher_.StopWatching();
 #endif
 
   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                           base::Bind(&NotifyProcessHostConnected, data_));
 
   delegate_->OnChannelConnected(peer_pid);
 
   if (IsProcessLaunched()) {
+    ShareMetricsAllocatorToProcess();
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                             base::Bind(&NotifyProcessLaunchedAndConnected,
                                        data_));
   }
 }
 
 void BrowserChildProcessHostImpl::OnChannelError() {
   delegate_->OnChannelError();
 }
 
@@ skipping 81 matching lines @@
     }
 #endif
   }
   delete delegate_;  // Will delete us
 }
 
 bool BrowserChildProcessHostImpl::Send(IPC::Message* message) {
   return child_process_host_->Send(message);
 }
 
+void BrowserChildProcessHostImpl::CreateMetricsAllocator() {
+  // Create a persistent memory segment for subprocess histograms only if
+  // they're active in the browser.
+  // TODO(bcwhite): Remove this once persistence is always enabled.
+  if (!base::GlobalHistogramAllocator::Get())
+    return;
+
+  // Determine the correct parameters based on the process type.
+  size_t memory_size;
+  base::StringPiece metrics_name;
+  switch (data_.process_type) {
+    case PROCESS_TYPE_GPU:
+      memory_size = 100 << 10;  // 100 KiB
+      metrics_name = "GpuMetrics";
+      break;
+
+    default:
+      return;
+  }
+
+  // Create the shared memory segment and attach an allocator to it.
+  // Mapping the memory shouldn't fail but be safe if it does; everything
+  // will continue to work but just as if persistence weren't available.
+  std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory());
+  if (!shm->CreateAndMapAnonymous(memory_size))
+    return;
+  metrics_allocator_.reset(new base::SharedPersistentMemoryAllocator(
+      std::move(shm), static_cast<uint64_t>(data_.id), metrics_name,
+      /*readonly=*/false));
+}
+
+void BrowserChildProcessHostImpl::ShareMetricsAllocatorToProcess() {
+  if (metrics_allocator_) {
+    base::SharedMemoryHandle shm_handle;
+    metrics_allocator_->shared_memory()->ShareToProcess(data_.handle,
+                                                        &shm_handle);
+    Send(new ChildProcessMsg_SetHistogramMemory(
+        shm_handle, metrics_allocator_->shared_memory()->mapped_size()));
+  }
+}
+
 void BrowserChildProcessHostImpl::OnProcessLaunchFailed(int error_code) {
   delegate_->OnProcessLaunchFailed(error_code);
   notify_child_disconnected_ = false;
   delete delegate_;  // Will delete us
 }
 
 void BrowserChildProcessHostImpl::OnProcessLaunched() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   const base::Process& process = child_process_->GetProcess();
   DCHECK(process.IsValid());
 
 #if defined(OS_WIN)
   // Start a WaitableEventWatcher that will invoke OnProcessExitedEarly if the
   // child process exits. This watcher is stopped once the IPC channel is
   // connected and the exit of the child process is detecter by an error on the
   // IPC channel thereafter.
   DCHECK(!early_exit_watcher_.GetWatchedObject());
   early_exit_watcher_.StartWatchingOnce(process.Handle(), this);
 #endif
 
   // TODO(rvargas) crbug.com/417532: Don't store a handle.
   data_.handle = process.Handle();
   delegate_->OnProcessLaunched();
 
   if (is_channel_connected_) {
+    ShareMetricsAllocatorToProcess();
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                             base::Bind(&NotifyProcessLaunchedAndConnected,
                                        data_));
   }
 }
 
 bool BrowserChildProcessHostImpl::IsProcessLaunched() const {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   return child_process_.get() && child_process_->GetProcess().IsValid();
@@ skipping 28 matching lines @@
 
 #if defined(OS_WIN)
 
 void BrowserChildProcessHostImpl::OnObjectSignaled(HANDLE object) {
   OnChildDisconnected();
 }
 
 #endif
 
 }  // namespace content