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POWhy does my application wait for synchronization so much?
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  1. POWhy does my application wait for synchronization so much?
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    copied!<p>I am working on a performance test which involves several clients bombarding the server with 150 requests each, as fast as they can.</p> <p>The server is constructed from 3 WCF services, one is opened to outside with httpbinding, it talks to 2 other services via net.pipe (IPC). one of the services is in charge of DB connections (SQL server 2008 R2).</p> <p>This DB connection service uses the following connection string enhancments:</p> <pre><code>Min Pool Size=20; Max Pool Size=1000; Connection Timeout=20; </code></pre> <p>and is WCF throttled(like all other WCF services).</p> <p>I noticed that when I activate 1 client it may take 3 seconds, but when I activate 3 clients it may take 8-9 or more.</p> <p>I checked with the SQL server profiler to see how many concurrent processes are used, and I saw that only about 8 processes are being used.</p> <p>So I realized that somewhere in the server the requests get queued instead of concurrently processed.</p> <p>In order to get to the bottom of it I've used a performance profiler (ANTS to be exact) which showed me that about 70% of the time was wasted on <strong>"Waiting for synchronization</strong></p> <p>When I open the call graph I find two things that look strange but I'm not sure what they mean:</p> <ol> <li>System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke is being used in the top of the tree, is that ok for concurrent processing?</li> <li>All synchronized problems involve some kind of SQL Server activity, like ExecuteNonQuery, ExecuteReader and so on (When I get to the bottom of the call tree)</li> </ol> <p>I noticed that the DB connection service uses a DAL project(some legacy code, unfortunately) which is totally static.</p> <p>After reading <a href="https://stackoverflow.com/questions/3037637/c-sharp-what-if-a-static-method-is-called-from-multiple-threads">this</a> I'm not sure if DAL's code is problematic or not, here is a sample of a stored procedure call.</p> <pre><code> public static int PerformStoredProcedure(string storedP,string ext,out string msg) { msg = ""; SqlCommand command = GetSqlCommand(storedP,ext); command.Connection.Open(); int result = (int)PerformStoredProcedure(command,out msg); command.Connection.Close(); return result; } </code></pre> <p>This Method is usualy called from the DB connection service:</p> <pre><code> public static int PerformStoredProcedureWithParams(string storedP,string ext,out string msg, params object[] pars) { msg = ""; SqlCommand command = GetSqlCommand(storedP,ext); UpdateCommandParams(command, pars); command.Connection.Open(); int result = (int)PerformStoredProcedure(command,out msg); command.Connection.Close(); return result; } </code></pre> <p>So, is there anything wrong here?</p> <p>Or maybe I should look somewhere else?</p> <p><strong>Edit:</strong></p> <p>After Brijesh's comment I realized I hadn't change the default InstanceContextMode and ConcurrencyMode of the WCF services... Kind of beginner's mistake I guess.</p> <p>I'm still not certain if I should use PerSession/Multiple or PerCall/ Single. As I see it each service should handle each request as on object, regardless of the client.</p> <p>What should I use?</p> <p><strong>2nd EDIT:</strong></p> <p>After using PerCall and PerSession/Multiple, I noticed that there is still no change (at least in the DB service). what I see is that the main entry point service may open up alot of threads, but only a few (still around 8-10 threads) are opened at the DB connection service.</p> <p>is there any other reason why this can happen? I ruled out DAL being a problem because not enough requests go in the DB service so I figure its something in the service or something in the clients...</p> <p><strong>3rd EDIT:</strong></p> <p>Here are the config files:</p> <p>Manager's config wcf service section:</p> <pre><code>&lt;services&gt; &lt;service behaviorConfiguration="ServicesBehavior" name="Verifone.GenericPP.GPPManagerService.GPPManagerServiceImpl"&gt; &lt;host&gt; &lt;baseAddresses&gt; &lt;add baseAddress="http://localhost:9090/GPPManagerService/"/&gt; &lt;/baseAddresses&gt; &lt;/host&gt; &lt;endpoint contract="Verifone.GenericPP.GPPManagerService.IGPPManagerService" binding="basicHttpBinding" address="GPPManagerService"&gt;&lt;/endpoint&gt; &lt;/service&gt; &lt;/services&gt; &lt;behaviors&gt; &lt;serviceBehaviors&gt; &lt;behavior name="ServicesBehavior"&gt; &lt;!--amith 13-05-2012--&gt; &lt;serviceThrottling maxConcurrentCalls="1000" maxConcurrentSessions="1000" maxConcurrentInstances="1000" /&gt; &lt;serviceMetadata httpGetEnabled="true" /&gt; &lt;serviceDebug includeExceptionDetailInFaults="true" /&gt; &lt;/behavior&gt; &lt;/serviceBehaviors&gt; &lt;/behaviors&gt; &lt;bindings&gt; &lt;basicHttpBinding&gt; &lt;binding name="basicHttpBinding" maxBufferSize="10000000" maxReceivedMessageSize="10000000"&gt; &lt;readerQuotas maxStringContentLength="10000000" maxArrayLength="10000000"/&gt; &lt;security mode="None"&gt; &lt;transport clientCredentialType="None"/&gt; &lt;/security&gt; &lt;/binding&gt; </code></pre> <p>Manager's clients:</p> <pre><code> &lt;endpoint name="endpoint1" contract="IDBConnectionContract" bindingConfiguration="basicHttpBinding" binding="basicHttpBinding" address="http://localhost:9010/DBConnectionService/DBService"&gt;&lt;/endpoint&gt; &lt;endpoint name="endpoint2" contract="IGPPService" bindingConfiguration="basicHttpBinding" binding="basicHttpBinding" address="http://localhost:9095/GenericPPService/GenericPPService"&gt;&lt;/endpoint&gt; </code></pre> <p>DB Connection Service:</p> <pre><code>&lt;service behaviorConfiguration="ServicesBehavior" name="Verifone.DBConnectionService.DBConnectionContracImpl"&gt; &lt;host&gt; &lt;baseAddresses&gt; &lt;add baseAddress="http://localhost:9010/DBConnectionService/"/&gt; &lt;add baseAddress="net.pipe://localhost/DBConnectionService/"/&gt; &lt;/baseAddresses&gt; &lt;/host&gt; &lt;endpoint contract="Verifone.DBConnectionService.IDBConnectionContract" binding="basicHttpBinding" address="DBService"&gt;&lt;/endpoint&gt; &lt;endpoint contract="Verifone.DBConnectionService.IDBConnectionContract" binding="netNamedPipeBinding" bindingConfiguration="NetNamedPipeBinding_Configuration" address="" name="pipeEndpoint"/&gt; &lt;/service&gt; </code></pre> <p>The business logic service's client is pretty much the same like the Manager's.</p> <p>All services are self hosted and I have a DBConnectionProxy class at Manager's and Business code which they activate like this:</p> <pre><code> DBConnectionContractClient _dbConnectionContractClient = null; try { objDBConnectionContractClient = new DBConnectionContractClient(); objDBConnectionContractClient.ExecuteStoredProcedure(input, out result); } </code></pre>
 

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