Enable spare RenderProcessHost to be preinitialized.

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 445 matching lines @@
   void Release(int old_route_id) {
     session_storage_namespaces_awaiting_close_->erase(old_route_id);
   }
 
  private:
   std::unique_ptr<std::map<int, SessionStorageNamespaceMap>>
       session_storage_namespaces_awaiting_close_;
   DISALLOW_COPY_AND_ASSIGN(SessionStorageHolder);
 };
 
+// This class manages spare RenderProcessHosts.
+//
+// There is a singleton instance of this class which manages a single spare
+// renderer (g_spare_render_process_host_manager, below). This class
+// encapsulates the implementation of
+// RenderProcessHost::WarmupSpareRenderProcessHost()
+//
+// RenderProcessHostImpl should call
+// SpareRenderProcessHostManager::MaybeTakeSpareRenderProcessHost when creating
+// a new RPH. In this implementation, the spare renderer is bound to a
+// BrowserContext and its default StoragePartition. If
+// MaybeTakeSpareRenderProcessHost is called with a BrowserContext and
+// StoragePartition that does not match, the spare renderer is discarded. In
+// particular, only the default StoragePartition will be able to use a spare
+// renderer. The spare renderer will also not be used as a guest renderer
+// (is_for_guests_ == true).
+//
+// It is safe to call WarmupSpareRenderProcessHost multiple times, although if
+// called in a context where the spare renderer is not likely to be used
+// performance may suffer due to the unnecessary RPH creation.
+class SpareRenderProcessHostManager : public RenderProcessHostObserver {
+ public:
+  SpareRenderProcessHostManager() {}
+
+  void WarmupSpareRenderProcessHost(BrowserContext* browser_context) {
+    StoragePartitionImpl* current_partition =
+        static_cast<StoragePartitionImpl*>(
+            BrowserContext::GetStoragePartition(browser_context, nullptr));
+
+    if (spare_render_process_host_ &&
+        matching_browser_context_ == browser_context &&
+        matching_storage_partition_ == current_partition)
+      return;  // Nothing to warm up.
+
+    CleanupSpareRenderProcessHost();
+
+    // Don't create a spare renderer if we're running a single renderer or if

[Charlie Reis, 2017/06/29 21:09:17]

nit: s/running a single renderer/using --single-process/

[mattcary, 2017/06/30 12:37:56]

Done.

+    // we've got too many processes. See also ShouldTryToUseExistingProcessHost
+    // in this file.
+    if (RenderProcessHost::run_renderer_in_process() ||
+        g_all_hosts.Get().size() >=
+            RenderProcessHostImpl::GetMaxRendererProcessCount())
+      return;
+
+    matching_browser_context_ = browser_context;
+    matching_storage_partition_ = current_partition;
+
+    spare_render_process_host_ = RenderProcessHostImpl::CreateRenderProcessHost(
+        browser_context, current_partition, false /* is_for_guests_only */);
+    spare_render_process_host_->AddObserver(this);
+    spare_render_process_host_->Init();
+  }
+
+  RenderProcessHost* MaybeTakeSpareRenderProcessHost(
+      const BrowserContext* browser_context,
+      const StoragePartition* partition,
+      bool is_for_guests_only) {
+    if (!spare_render_process_host_ ||
+        browser_context != matching_browser_context_ ||
+        partition != matching_storage_partition_ || is_for_guests_only) {
+      // As a new RenderProcessHost will almost certainly be created, we cleanup
+      // the non-matching one so as not to waste resources.
+      CleanupSpareRenderProcessHost();
+      return nullptr;
+    }
+
+    RenderProcessHost* rph = spare_render_process_host_;

[Charlie Reis, 2017/06/29 21:09:16]

As I mentioned earlier, I think we should include checks here for the following
things now that we're handling the random reuse case:
 - listeners_.IsEmpty() should be true
 - GetWorkerRefCount() should be 0
 - pending_views_ should be 0

If those fail, it means we're putting things in the spare RPH without meaning
to.  I'd suggest having them be CHECKs, since DCHECKs won't fire in the wild and
we won't learn anything unless existing tests happen to hit them.

[mattcary, 2017/06/30 12:37:56]

Done. I had thought that was in the context of not using a spare renderer in
GetExistingProccessHost which is not what we ended up doing. I grok now.

This required extending the RPHImpl public interface. I think that I properly
characterized the difference between what we want to do and the existing
RPH::IsUnused() flag, but can you confirm?

+    DropSpareRenderProcessHost(spare_render_process_host_);
+    return rph;
+  }
+
+  // Remove |host| as a possible spare renderer. Does not shut it down cleanly;
+  // the assumption is that the host was shutdown somewhere else and has
+  // notifying the SpareRenderProcessHostManager.
+  void DropSpareRenderProcessHost(RenderProcessHost* host) {
+    if (spare_render_process_host_ && spare_render_process_host_ == host) {
+      spare_render_process_host_->RemoveObserver(this);
+      spare_render_process_host_ = nullptr;
+    }
+  }
+
+  RenderProcessHost* spare_render_process_host() {
+    return spare_render_process_host_;
+  }
+
+ private:
+  // RenderProcessHostObserver
+  void RenderProcessWillExit(RenderProcessHost* host) override {
+    DropSpareRenderProcessHost(host);
+  }
+
+  void RenderProcessExited(RenderProcessHost* host,
+                           base::TerminationStatus unused_status,
+                           int unused_exit_code) override {
+    DropSpareRenderProcessHost(host);
+  }
+
+  void RenderProcessHostDestroyed(RenderProcessHost* host) override {
+    DropSpareRenderProcessHost(host);
+  }
+
+  void CleanupSpareRenderProcessHost() {
+    if (spare_render_process_host_) {
+      spare_render_process_host_->Cleanup();
+      DropSpareRenderProcessHost(spare_render_process_host_);
+    }
+  }
+
+  // This is a bare pointer, because RenderProcessHost manages the lifetime of
+  // all its instances; see g_all_hosts, above.
+  RenderProcessHost* spare_render_process_host_;
+
+  // Used only to check if a creation request matches the spare, and not
+  // accessed.
+  const BrowserContext* matching_browser_context_ = nullptr;
+  const StoragePartition* matching_storage_partition_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(SpareRenderProcessHostManager);
+};
+
+base::LazyInstance<SpareRenderProcessHostManager>::Leaky
+    g_spare_render_process_host_manager = LAZY_INSTANCE_INITIALIZER;
+
 const void* const kDefaultSubframeProcessHostHolderKey =
     &kDefaultSubframeProcessHostHolderKey;
 
 class DefaultSubframeProcessHostHolder : public base::SupportsUserData::Data,
                                          public RenderProcessHostObserver {
  public:
   explicit DefaultSubframeProcessHostHolder(BrowserContext* browser_context)
       : browser_context_(browser_context) {}
   ~DefaultSubframeProcessHostHolder() override {}
 
   // Gets the correct render process to use for this SiteInstance.
   RenderProcessHost* GetProcessHost(SiteInstance* site_instance,
                                     bool is_for_guests_only) {
-    StoragePartition* default_partition =
-        BrowserContext::GetDefaultStoragePartition(browser_context_);
-    StoragePartition* partition =
-        BrowserContext::GetStoragePartition(browser_context_, site_instance);
+    StoragePartitionImpl* default_partition =
+        static_cast<StoragePartitionImpl*>(
+            BrowserContext::GetDefaultStoragePartition(browser_context_));
+    StoragePartitionImpl* partition = static_cast<StoragePartitionImpl*>(
+        BrowserContext::GetStoragePartition(browser_context_, site_instance));
 
     // Is this the default storage partition? If it isn't, then just give it its
     // own non-shared process.
     if (partition != default_partition || is_for_guests_only) {
-      RenderProcessHostImpl* host = new RenderProcessHostImpl(
-          browser_context_, static_cast<StoragePartitionImpl*>(partition),
-          is_for_guests_only);
+      RenderProcessHost* host = RenderProcessHostImpl::CreateRenderProcessHost(
+          browser_context_, partition, is_for_guests_only);
       host->SetIsNeverSuitableForReuse();
       return host;
     }
 
     // If we already have a shared host for the default storage partition, use
     // it.
     if (host_)
       return host_;
 
-    host_ = new RenderProcessHostImpl(
-        browser_context_, static_cast<StoragePartitionImpl*>(partition),
-        false /* for guests only */);
+    host_ = RenderProcessHostImpl::CreateOrUseSpareRenderProcessHost(
+        browser_context_, partition, false /* is for guests only */);
     host_->SetIsNeverSuitableForReuse();
     host_->AddObserver(this);
 
     return host_;
   }
 
   // Implementation of RenderProcessHostObserver.
   void RenderProcessHostDestroyed(RenderProcessHost* host) override {
     DCHECK_EQ(host_, host);
     host_->RemoveObserver(this);
     host_ = nullptr;
   }
 
  private:
   BrowserContext* browser_context_;
 
   // The default subframe render process used for the default storage partition
   // of this BrowserContext.
-  RenderProcessHostImpl* host_ = nullptr;
+  RenderProcessHost* host_ = nullptr;
 };
 
 void CreateMemoryCoordinatorHandle(
     int render_process_id,
     const service_manager::BindSourceInfo& source_info,
     mojom::MemoryCoordinatorHandleRequest request) {
   MemoryCoordinatorImpl::GetInstance()->CreateHandle(render_process_id,
                                                      std::move(request));
 }
 
@@ skipping 491 matching lines @@
     max_count = std::min(max_count, kMaxRendererProcessCount);
   }
   return max_count;
 }
 
 // static
 void RenderProcessHost::SetMaxRendererProcessCount(size_t count) {
   g_max_renderer_count_override = count;
 }
 
+// static
+RenderProcessHost* RenderProcessHostImpl::CreateRenderProcessHost(
+    BrowserContext* browser_context,
+    StoragePartitionImpl* storage_partition_impl,
+    bool is_for_guests_only) {
+  if (g_render_process_host_factory_) {
+    return g_render_process_host_factory_->CreateRenderProcessHost(
+        browser_context);
+  }
+
+  return new RenderProcessHostImpl(browser_context, storage_partition_impl,
+                                   is_for_guests_only);
+}
+
+// static
+RenderProcessHost* RenderProcessHostImpl::CreateOrUseSpareRenderProcessHost(
+    BrowserContext* browser_context,
+    StoragePartitionImpl* storage_partition_impl,
+    bool is_for_guests_only) {
+  RenderProcessHost* render_process_host =
+      g_spare_render_process_host_manager.Get().MaybeTakeSpareRenderProcessHost(
+          browser_context, storage_partition_impl, is_for_guests_only);
+
+  if (!render_process_host) {
+    render_process_host = CreateRenderProcessHost(
+        browser_context, storage_partition_impl, is_for_guests_only);
+  }
+
+  DCHECK(render_process_host);
+  return render_process_host;
+}
+
 RenderProcessHostImpl::RenderProcessHostImpl(
     BrowserContext* browser_context,
     StoragePartitionImpl* storage_partition_impl,
     bool is_for_guests_only)
     : fast_shutdown_started_(false),
       deleting_soon_(false),
 #ifndef NDEBUG
       is_self_deleted_(false),
 #endif
       pending_views_(0),
@@ skipping 1064 matching lines @@
   SiteProcessCountTracker* tracker = static_cast<SiteProcessCountTracker*>(
       browser_context->GetUserData(kPendingSiteProcessCountTrackerKey));
   if (!tracker) {
     tracker = new SiteProcessCountTracker();
     browser_context->SetUserData(kPendingSiteProcessCountTrackerKey,
                                  base::WrapUnique(tracker));
   }
   tracker->DecrementSiteProcessCount(site_url, render_process_host->GetID());
 }
 
+// static
+RenderProcessHost*
+RenderProcessHostImpl::GetSpareRenderProcessHostForTesting() {
+  return g_spare_render_process_host_manager.Get().spare_render_process_host();
+}
+
 bool RenderProcessHostImpl::IsForGuestsOnly() const {
   return is_for_guests_only_;
 }
 
 StoragePartition* RenderProcessHostImpl::GetStoragePartition() const {
   return storage_partition_impl_;
 }
 
 static void AppendCompositorCommandLineFlags(base::CommandLine* command_line) {
   command_line->AppendSwitchASCII(
@@ skipping 934 matching lines @@
     // Otherwise, if this process has been used to host any other content, it
     // cannot be reused if the destination site indeed requires a dedicated
     // process and can be locked to just that site.
     return false;
   }
 
   return GetContentClient()->browser()->IsSuitableHost(host, site_url);
 }
 
 // static
+void RenderProcessHost::WarmupSpareRenderProcessHost(
+    content::BrowserContext* browser_context) {
+  g_spare_render_process_host_manager.Get().WarmupSpareRenderProcessHost(
+      browser_context);
+}
+
+// static
 bool RenderProcessHost::run_renderer_in_process() {
   return g_run_renderer_in_process_;
 }
 
 // static
 void RenderProcessHost::SetRunRendererInProcess(bool value) {
   g_run_renderer_in_process_ = value;
 
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (value) {
@@ skipping 57 matching lines @@
                                               browser_context, site_url)) {
       suitable_renderers.push_back(iter.GetCurrentValue());
     }
     iter.Advance();
   }
 
   // Now pick a random suitable renderer, if we have any.
   if (!suitable_renderers.empty()) {
     int suitable_count = static_cast<int>(suitable_renderers.size());
     int random_index = base::RandInt(0, suitable_count - 1);
+    g_spare_render_process_host_manager.Get().DropSpareRenderProcessHost(
+        suitable_renderers[random_index]);

[Charlie Reis, 2017/06/29 21:09:16]

Sure, that seems like an ok way to handle it.  Please include a comment, like:

If this happened to be the spare RenderProcessHost, don't treat it as a spare
anymore.

[mattcary, 2017/06/30 12:37:56]

Done.

     return suitable_renderers[random_index];
   }
 
   return NULL;
 }
 
 // static
 bool RenderProcessHost::ShouldUseProcessPerSite(BrowserContext* browser_context,
                                                 const GURL& url) {
   // Returns true if we should use the process-per-site model.  This will be
@@ skipping 106 matching lines @@
     render_process_host = UnmatchedServiceWorkerProcessTracker::MatchWithSite(
         browser_context, site_url);
   }
 
   // If not (or if none found), see if we should reuse an existing process.
   if (!render_process_host &&
       ShouldTryToUseExistingProcessHost(browser_context, site_url)) {
     render_process_host = GetExistingProcessHost(browser_context, site_url);
   }
 
-  // Otherwise (or if that fails), create a new one.
+  // Before creating a new process, try to use a spare process if one is found.
+  StoragePartitionImpl* partition = static_cast<StoragePartitionImpl*>(
+      BrowserContext::GetStoragePartition(browser_context, site_instance));
   if (!render_process_host) {
-    if (g_render_process_host_factory_) {
-      render_process_host =
-          g_render_process_host_factory_->CreateRenderProcessHost(
-              browser_context);
-    } else {
-      StoragePartitionImpl* partition = static_cast<StoragePartitionImpl*>(
-          BrowserContext::GetStoragePartition(browser_context, site_instance));
-      render_process_host = new RenderProcessHostImpl(
-          browser_context, partition, is_for_guests_only);
-    }
+    render_process_host = CreateOrUseSpareRenderProcessHost(
+        browser_context, partition, is_for_guests_only);
   }
 
   if (is_unmatched_service_worker) {
     UnmatchedServiceWorkerProcessTracker::Register(
         browser_context, render_process_host, site_url);
   }
   return render_process_host;
 }
 
 void RenderProcessHostImpl::CreateSharedRendererHistogramAllocator() {
@@ skipping 492 matching lines @@
   LOG(ERROR) << "Terminating render process for bad Mojo message: " << error;
 
   // The ReceivedBadMessage call below will trigger a DumpWithoutCrashing.
   // Capture the error message in a crash key value.
   base::debug::ScopedCrashKey error_key_value("mojo-message-error", error);
   bad_message::ReceivedBadMessage(render_process_id,
                                   bad_message::RPH_MOJO_PROCESS_ERROR);
 }
 
 }  // namespace content