PlzNavigate: Add metrics to understand bf navigations PLT regression

content/browser/loader/resource_dispatcher_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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 254 matching lines @@
     return;
 
   if (result) {
     ResourceHostMsg_SyncLoad::WriteReplyParams(sync_result.get(), *result);
   } else {
     sync_result->set_reply_error();
   }
   filter->Send(sync_result.release());
 }
 
+// Used to log the cache flags for back-forward navigation requests.
+// Because this enum is used to back a histogrma, DO NOT REMOVE OR RENAME VALUES
+// in this enum. Instead, add a new one at the end.
+// TODO(clamy): Remove this once we know the reason behind PlzNavigate's
+// regression on PLT for back forward navigations.
+enum HistogramCacheFlag {
+  HISTOGRAM_VALIDATE_CACHE,
+  HISTOGRAM_BYPASS_CACHE,
+  HISTOGRAM_SKIP_CACHE_VALIDATION,
+  HISTOGRAM_ONLY_FROM_CACHE,
+  HISTOGRAM_DISABLE_CACHE,
+  HISTOGRAM_CACHE_FLAG_MAX = HISTOGRAM_DISABLE_CACHE,
+};
+
+void RecordCacheFlags(HistogramCacheFlag flag) {
+  UMA_HISTOGRAM_ENUMERATION("Navigation.BackForward.CacheFlags", flag,
+                            HISTOGRAM_CACHE_FLAG_MAX);
+}
+
+void LogBackForwardNavigationFlagsHistogram(int load_flags) {
+  if (load_flags & net::LOAD_VALIDATE_CACHE)
+    RecordCacheFlags(HISTOGRAM_VALIDATE_CACHE);
+
+  if (load_flags & net::LOAD_BYPASS_CACHE)
+    RecordCacheFlags(HISTOGRAM_BYPASS_CACHE);
+
+  if (load_flags & net::LOAD_SKIP_CACHE_VALIDATION)
+    RecordCacheFlags(HISTOGRAM_SKIP_CACHE_VALIDATION);
+
+  if (load_flags & net::LOAD_ONLY_FROM_CACHE)
+    RecordCacheFlags(HISTOGRAM_ONLY_FROM_CACHE);
+
+  if (load_flags & net::LOAD_DISABLE_CACHE)
+    RecordCacheFlags(HISTOGRAM_DISABLE_CACHE);
+}
+
 }  // namespace
 
 ResourceDispatcherHostImpl::LoadInfo::LoadInfo() {}
 ResourceDispatcherHostImpl::LoadInfo::LoadInfo(const LoadInfo& other) = default;
 ResourceDispatcherHostImpl::LoadInfo::~LoadInfo() {}
 
 ResourceDispatcherHostImpl::HeaderInterceptorInfo::HeaderInterceptorInfo() {}
 
 ResourceDispatcherHostImpl::HeaderInterceptorInfo::~HeaderInterceptorInfo() {}
 
@@ skipping 1908 matching lines @@
   return kAvgBytesPerOutstandingRequest + strings_cost;
 }
 
 void ResourceDispatcherHostImpl::BeginRequestInternal(
     std::unique_ptr<net::URLRequest> request,
     std::unique_ptr<ResourceHandler> handler) {
   DCHECK(!request->is_pending());
   ResourceRequestInfoImpl* info =
       ResourceRequestInfoImpl::ForRequest(request.get());
 
+  // Log metrics for back-forward navigations.
+  // TODO(clamy): Remove this once we understand the reason behind the
+  // back-forward PLT regression with PlzNavigate
+  if ((info->GetPageTransition() & ui::PAGE_TRANSITION_FORWARD_BACK) &&
+      IsResourceTypeFrame(info->GetResourceType())) {
+    LogBackForwardNavigationFlagsHistogram(request->load_flags());
+  }
+
   if ((TimeTicks::Now() - last_user_gesture_time_) <
       TimeDelta::FromMilliseconds(kUserGestureWindowMs)) {
     request->SetLoadFlags(request->load_flags() | net::LOAD_MAYBE_USER_GESTURE);
   }
 
   // Add the memory estimate that starting this request will consume.
   info->set_memory_cost(CalculateApproximateMemoryCost(request.get()));
 
   // If enqueing/starting this request will exceed our per-process memory
   // bound, abort it right away.
@@ skipping 443 matching lines @@
                                  &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content