Slow start pipelining.

net/http/http_pipelined_host_impl.cc

+// Copyright (c) 2011 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 "net/http/http_pipelined_host_impl.h"
+
+#include "base/stl_util.h"
+#include "net/http/http_pipelined_connection_impl.h"
+#include "net/http/http_pipelined_stream.h"
+
+namespace net {
+
+// TODO(simonjam): Run experiments to see what value minimizes evictions without
+// costing too much performance. Until then, this is just a bad guess.
+static const int kNumKnownSuccessesThreshold = 3;
+
+class HttpPipelinedConnectionImplFactory :
+    public HttpPipelinedConnection::Factory {
+ public:
+  HttpPipelinedConnection* CreateNewPipeline(
+      ClientSocketHandle* connection,
+      HttpPipelinedConnection::Delegate* delegate,
+      const SSLConfig& used_ssl_config,
+      const ProxyInfo& used_proxy_info,
+      const BoundNetLog& net_log,
+      bool was_npn_negotiated) OVERRIDE {
+    return new HttpPipelinedConnectionImpl(connection, delegate,
+                                           used_ssl_config, used_proxy_info,
+                                           net_log, was_npn_negotiated);
+  }
+};
+
+HttpPipelinedHostImpl::HttpPipelinedHostImpl(
+    HttpPipelinedHost::Delegate* delegate,
+    const HostPortPair& origin,
+    HttpPipelinedConnection::Factory* factory,
+    Capability capability)
+    : delegate_(delegate),
+      origin_(origin),
+      factory_(factory),
+      capability_(capability) {
+  if (!factory) {
+    factory_.reset(new HttpPipelinedConnectionImplFactory());
+  }
+}
+
+HttpPipelinedHostImpl::~HttpPipelinedHostImpl() {
+  CHECK(pipelines_.empty());
+}
+
+HttpPipelinedStream* HttpPipelinedHostImpl::CreateStreamOnNewPipeline(
+    ClientSocketHandle* connection,
+    const SSLConfig& used_ssl_config,
+    const ProxyInfo& used_proxy_info,
+    const BoundNetLog& net_log,
+    bool was_npn_negotiated) {
+  HttpPipelinedConnection* pipeline = factory_->CreateNewPipeline(
+      connection, this, used_ssl_config, used_proxy_info, net_log,
+      was_npn_negotiated);
+  PipelineInfo info;
+  switch (capability_) {
+    case CAPABLE:
+      info.capacity = max_pipeline_depth();
+      break;
+
+    case INCAPABLE:
+      CHECK(false);
+
+    case UNKNOWN:
+      info.capacity = 1;
+      break;
+  }
+  pipelines_.insert(std::make_pair(pipeline, info));
+  return pipeline->CreateNewStream();
+}
+
+HttpPipelinedStream* HttpPipelinedHostImpl::CreateStreamOnExistingPipeline() {
+  HttpPipelinedConnection* available_pipeline = NULL;
+  for (PipelineInfoMap::iterator it = pipelines_.begin();
+       it != pipelines_.end(); ++it) {
+    if (it->first->usable() &&
+        it->first->active() &&
+        it->first->depth() < it->second.capacity &&
+        (!available_pipeline ||
+         it->first->depth() < available_pipeline->depth())) {
+      available_pipeline = it->first;
+    }
+  }
+  if (!available_pipeline) {
+    return NULL;
+  }
+  return available_pipeline->CreateNewStream();
+}
+
+bool HttpPipelinedHostImpl::IsExistingPipelineAvailable() {
+  for (PipelineInfoMap::iterator it = pipelines_.begin();
+       it != pipelines_.end(); ++it) {
+    if (it->first->usable() &&
+        it->first->active() &&
+        it->first->depth() < it->second.capacity) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const HostPortPair& HttpPipelinedHostImpl::origin() const {
+  return origin_;
+}
+
+void HttpPipelinedHostImpl::OnPipelineEmpty(HttpPipelinedConnection* pipeline) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  if (capability_ == UNKNOWN &&
+      pipelines_[pipeline].num_successes >= kNumKnownSuccessesThreshold) {
+    capability_ = CAPABLE;

[mmenke, 2011/11/28 23:05:28]

Seems a little weird to wait until shutting down a connection to do this. 
Suppose it's not as delayed as it seems at first, since this just happens
whenever we run out of requests, rather than when we close the socket.

[James Simonsen, 2011/12/01 01:17:10]

Done.

Yeah, I don't think it matters in practice, so I'll do it where I think you
expected it, to make it more readable.

+    delegate_->OnHostDeterminedCapability(this, CAPABLE);
+  }
+  pipelines_.erase(pipeline);
+  delete pipeline;
+  if (pipelines_.empty()) {
+    delegate_->OnHostIdle(this);
+    // WARNING: We'll probably be deleted here.
+  }
+}
+
+void HttpPipelinedHostImpl::OnPipelineHasCapacity(
+    HttpPipelinedConnection* pipeline) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  if (pipeline->usable() &&
+      capability_ != INCAPABLE &&
+      pipeline->depth() < pipelines_[pipeline].capacity) {
+    delegate_->OnHostHasAdditionalCapacity(this);
+  }
+  if (!pipeline->depth()) {
+    OnPipelineEmpty(pipeline);
+    // WARNING: We might be deleted here.
+  }
+}
+
+void HttpPipelinedHostImpl::OnPipelineFeedback(
+    HttpPipelinedConnection* pipeline,
+    HttpPipelinedConnection::Feedback feedback) {
+  CHECK(ContainsKey(pipelines_, pipeline));
+  switch (feedback) {
+    case HttpPipelinedConnection::OK:
+      ++pipelines_[pipeline].num_successes;
+      if (pipelines_[pipeline].capacity != max_pipeline_depth()) {
+        pipelines_[pipeline].capacity = max_pipeline_depth();
+        OnPipelineHasCapacity(pipeline);
+      }
+      break;
+
+    case HttpPipelinedConnection::SOCKET_ERROR:
+    case HttpPipelinedConnection::OLD_HTTP_VERSION:
+      capability_ = INCAPABLE;
+      delegate_->OnHostDeterminedCapability(this, INCAPABLE);
+      break;
+
+    case HttpPipelinedConnection::MUST_CLOSE_CONNECTION:
+      break;
+  }
+}
+
+HttpPipelinedHostImpl::PipelineInfo::PipelineInfo()
+    : capacity(1),
+      num_successes(0) {
+}
+
+}  // namespace net