Add UMA that periodically logs number of outstanding requests

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 39108877eb551027f55ebfd7e6d29a13dc89690d..d3919eee0a6c3949abd2ce4965d71f00d0b0fb39 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -168,6 +168,9 @@ static ResourceDispatcherHostImpl* g_resource_dispatcher_host;
 // The interval for calls to ResourceDispatcherHostImpl::UpdateLoadStates
 const int kUpdateLoadStatesIntervalMsec = 250;
 
+// The interval for calls to RecordOutstandingRequestsStats.
+const int kRecordOutstandingRequestsStatsIntervalMsec = 60000;
+
 // Maximum byte "cost" of all the outstanding requests for a renderer.
 // See declaration of |max_outstanding_requests_cost_per_process_| for details.
 // This bound is 25MB, which allows for around 6000 outstanding requests.
@@ -339,6 +342,8 @@ ResourceDispatcherHostImpl::ResourceDispatcherHostImpl(
           kMaxOutstandingRequestsCostPerProcess),
       largest_outstanding_request_count_seen_(0),
       largest_outstanding_request_per_process_count_seen_(0),
+      peak_outstanding_request_count_(0),
+      peak_outstanding_request_count_multitab_(0),
       delegate_(nullptr),
       loader_delegate_(nullptr),
       allow_cross_origin_auth_prompt_(false),
@@ -361,6 +366,7 @@ ResourceDispatcherHostImpl::ResourceDispatcherHostImpl(
       base::Bind(&ResourceDispatcherHostImpl::OnInit, base::Unretained(this)));
 
   update_load_states_timer_.reset(new base::RepeatingTimer());
+  record_outstanding_requests_stats_timer_.reset(new base::RepeatingTimer());
 }
 
 // The default ctor is only used by unittests. It is reasonable to assume that
@@ -589,13 +595,20 @@ bool ResourceDispatcherHostImpl::HandleExternalProtocol(ResourceLoader* loader,
 }
 
 void ResourceDispatcherHostImpl::DidStartRequest(ResourceLoader* loader) {
-  // Make sure we have the load state monitor running.
+  // Make sure we have the load state monitors running.
   if (!update_load_states_timer_->IsRunning() &&
       scheduler_->HasLoadingClients()) {
     update_load_states_timer_->Start(
         FROM_HERE, TimeDelta::FromMilliseconds(kUpdateLoadStatesIntervalMsec),
         this, &ResourceDispatcherHostImpl::UpdateLoadInfo);
   }
+  if (!record_outstanding_requests_stats_timer_->IsRunning()) {
+    record_outstanding_requests_stats_timer_->Start(
+        FROM_HERE,
+        TimeDelta::FromMilliseconds(
+            kRecordOutstandingRequestsStatsIntervalMsec),
+        this, &ResourceDispatcherHostImpl::RecordOutstandingRequestsStats);
+  }
 }
 
 void ResourceDispatcherHostImpl::DidReceiveRedirect(
@@ -784,10 +797,11 @@ void ResourceDispatcherHostImpl::OnShutdown() {
   is_shutdown_ = true;
   pending_loaders_.clear();
 
-  // Make sure we shutdown the timer now, otherwise by the time our destructor
+  // Make sure we shutdown the timers now, otherwise by the time our destructor
   // runs if the timer is still running the Task is deleted twice (once by
   // the MessageLoop and the second time by RepeatingTimer).
   update_load_states_timer_.reset();
+  record_outstanding_requests_stats_timer_.reset();
 
   // Clear blocked requests if any left.
   // Note that we have to do this in 2 passes as we cannot call
@@ -1969,6 +1983,15 @@ ResourceDispatcherHostImpl::IncrementOutstandingRequestsCount(
         largest_outstanding_request_per_process_count_seen_);
   }
 
+  if (num_in_flight_requests_ > peak_outstanding_request_count_) {
+    peak_outstanding_request_count_ = num_in_flight_requests_;
+  }
+
+  if (outstanding_requests_stats_map_.size() >= 2 &&

[Takashi Toyoshima, 2017/06/20 07:39:21]

This will report if there is one background tab that has a long-polling request,
and it will be a very common case. Probably, we want to check if each map entry
isn't in the "network quiet" state.

[Kunihiko Sakamoto, 2017/06/20 08:39:28]

Done.

+      num_in_flight_requests_ > peak_outstanding_request_count_multitab_) {
+    peak_outstanding_request_count_multitab_ = num_in_flight_requests_;
+  }
+
   return stats;
 }
 
@@ -2497,6 +2520,22 @@ void ResourceDispatcherHostImpl::UpdateLoadInfo() {
       base::Bind(UpdateLoadStateOnUI, loader_delegate_, base::Passed(&infos)));
 }
 
+void ResourceDispatcherHostImpl::RecordOutstandingRequestsStats() {
+  if (peak_outstanding_request_count_ != 0) {
+    UMA_HISTOGRAM_COUNTS_1M(
+        "Net.ResourceDispatcherHost.PeakOutstandingRequests",
+        peak_outstanding_request_count_);
+    peak_outstanding_request_count_ = 0;

[Takashi Toyoshima, 2017/06/20 07:39:21]

this will not report at the next time if there are no inc/dec events in the next
timer period.
we may want to keep the current outstanding value?

[Kunihiko Sakamoto, 2017/06/20 08:39:28]

Good catch, thanks!
Done.

+  }
+
+  if (peak_outstanding_request_count_multitab_ != 0) {
+    UMA_HISTOGRAM_COUNTS_1M(
+        "Net.ResourceDispatcherHost.PeakOutstandingRequests.MultiTabLoading",
+        peak_outstanding_request_count_multitab_);
+    peak_outstanding_request_count_multitab_ = 0;
+  }
+}
+
 void ResourceDispatcherHostImpl::BlockRequestsForRoute(
     const GlobalFrameRoutingId& global_routing_id) {
   DCHECK(io_thread_task_runner_->BelongsToCurrentThread());