Change the default number of proxy resolver threads used for evaluating PAC s...

net/proxy/proxy_service.h

 // Copyright (c) 2010 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.
 
 #ifndef NET_PROXY_PROXY_SERVICE_H_
 #define NET_PROXY_PROXY_SERVICE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 119 matching lines @@
 
   // Forces refetching the proxy configuration, and applying it.
   // This re-does everything from fetching the system configuration,
   // to downloading and testing the PAC files.
   void ForceReloadProxyConfig();
 
   // Creates a proxy service that polls |proxy_config_service| to notice when
   // the proxy settings change. We take ownership of |proxy_config_service|.
   // Iff |use_v8_resolver| is true, then the V8 implementation is
   // used.
+  //
+  // |num_pac_threads| specifies the maximum number of threads to use for
+  // executing PAC scripts. Threads are created lazily on demand.
+  // If |0| is specified, then a default number of threads will be selected.
+  //
+  // Having more threads avoids stalling proxy resolve requests when the
+  // PAC script takes a while to run. This is particularly a problem when PAC
+  // scripts do synchronous DNS resolutions, since that can take on the order
+  // of seconds.
+  //
+  // However, the disadvantages of using more than 1 thread are:
+  //   (a) can cause compatibility issues for scripts that rely on side effects
+  //       between runs (such scripts should not be common though).
+  //   (b) increases the memory used by proxy resolving, as each thread will
+  //       duplicate its own script context.
+
   // |url_request_context| is only used when use_v8_resolver is true:
   // it specifies the URL request context that will be used if a PAC
   // script needs to be fetched.
   // |io_loop| points to the IO thread's message loop. It is only used
   // when pc is NULL.
   // ##########################################################################
   // # See the warnings in net/proxy/proxy_resolver_v8.h describing the
   // # multi-threading model. In order for this to be safe to use, *ALL* the
   // # other V8's running in the process must use v8::Locker.
   // ##########################################################################
   static ProxyService* Create(
       ProxyConfigService* proxy_config_service,
       bool use_v8_resolver,
+      size_t num_pac_threads,
       URLRequestContext* url_request_context,
       NetLog* net_log,
       MessageLoop* io_loop);
 
   // Convenience method that creates a proxy service using the
   // specified fixed settings. |pc| must not be NULL.
   static ProxyService* CreateFixed(const ProxyConfig& pc);
 
   // Creates a proxy service that always fails to fetch the proxy configuration,
   // so it falls back to direct connect.
@@ skipping 147 matching lines @@
 
   base::WaitableEvent event_;
   CompletionCallbackImpl<SyncProxyServiceHelper> callback_;
   ProxyInfo proxy_info_;
   int result_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_SERVICE_H_