System and Application Performance Counters for ASP.NET

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1

ASP.NET supports two groups of performance counters: system and application. The former is exposed in PerfMon in the ASP.NET performance counter object; the latter is exposed in the ASP.NET Applications performance object. There is a significant difference between the State Server Sessions counters found in the ASP.NET performance object, which apply only to the server computer on which the state server is running, and the Sessions counters found in the ASP.NET Applications performance object, which apply only to user sessions that occur in process.

Note

The value associated with each performance counter is updated every 400 milliseconds.

When monitoring the performance of your ASP.NET Web applications, you should always track the performance counters listed in the following table.

Performance object	Performance counter
ASP.NET	Application Restarts
ASP.NET	Requests Queued
ASP.NET	Worker Process Restarts
ASP.NET Applications	Errors Total
ASP.NET Applications	Requests/Sec
Processor	% CPU Utilization

The % CPU Utilization counter monitors CPU utilization on the Web server computer. Low CPU utilization or the inability to maximize CPU utilization regardless of client load can signify contention for resource or a lock in your Web application.

In addition, the performance counters listed in the following table can be valuable in determining problems with your Web applications' performance.

Performance object	Performance counter
ASP.NET Applications	Pipeline Instance Count
.NET CLR Exceptions	# of Exceps Thrown
System	Context Switches/sec

The # of Exceps Thrown counter displays the number of exceptions thrown in an application, since these can have performance implications. Some code paths, however, rely on exceptions for their proper functioning. For example, the HttpResponse.Redirect method always throws an uncatchable exception, ThreadAbortException. Therefore, it can be more useful to track the number of exceptions thrown using the Errors Total counter to see if the exception generated an error on the application.

The Context Switches/sec counter measures the rate at which thread contexts are switched by all CPUs in the Web server computer. A high number for this counter usually indicates either high contention in locks or many switches between user and kernel mode by the thread. Further investigation with sampling profilers and other tools might be warranted.

The counters in the ASP.NET and ASP.NET Applications performance objects are detailed in the following lists.

ASP.NET System Performance Counters

ASP.NET supports the following ASP.NET system performance counters. These aggregate information for all ASP.NET applications on a Web server computer, or they apply generally to a system of ASP.NET servers running the same applications. These can include Web farms and Web gardens.

Performance Counter	Description
Application Restarts	The number of times that an application has been restarted during the Web server's lifetime. Application restarts are incremented with each Application_OnEnd event. An application restart can occur because of changes to the Web.config file, changes to assemblies stored in the application's \Bin directory, or too many changes in Web Forms pages. Unexpected increases in this counter can mean that unforeseen problems are causing your Web application to shut down. In such circumstances you should investigate as soon as possible. Note This value is reset every time the Internet Information Services (IIS) host is restarted.
Application Running	The number of applications running on the server computer.
Requests Disconnected	The number of requests that have been disconnected due to a communication failure.
Requests Queued	The number of requests waiting for service from the queue. When this number starts to increment linearly with respect to client load, the Web server computer has reached the limit of concurrent requests that it can process. The default maximum for this counter is 5,000. You can change this setting in the computer's Machine.config file.
Requests Rejected	The total number of requests not executed because of insufficient server resources to process them. This counter represents the number of requests that return a 503 HTTP status code, indicating that the server is too busy.
Request Wait Time	The number of milliseconds that the most recent request waited for processing in the queue.
Session State Server Connections Total	The total number of session-state connections to the computer on which out-of-process session-state data is stored.
Session SQL Server Connections Total	The total number of session-state connections to the Microsoft SQL Server-TM- database in which session-state data is stored.
State Server Sessions Abandoned	The number of user sessions that have been explicitly abandoned. These are sessions that are ended by specific user actions, such as closing the browser or navigating to another site. This counter is available only on the computer where the state server service (aspnet_state) is running.
State Server Sessions Active	The number of currently active user sessions. This counter is available only on the computer where the state server service (aspnet_state) is running.
State Server Sessions Timed Out	The number of user sessions that have become inactive through user inaction. This counter is available only on the computer where the state server service (aspnet_state) is running.
State Server Sessions Total	The number of sessions created during the lifetime of the process. This counter is the cumulative value of State Server Sessions Active, State Server Sessions Abandoned, and State Server Sessions Timed Out. This counter is available only on the computer where the state server service (aspnet_state) is running.
Worker Process Restarts	The number of times a worker process has been restarted on the server computer. A worker process can be restarted if it fails unexpectedly or when it is intentionally recycled. In the case of unexpected increases in this counter you should investigate as soon as possible.
Worker Process Running	The number of worker processes running on the server computer.

ASP.NET Application Performance Counters

ASP.NET supports the following application performance counters, which you can use to monitor the performance of a single instance of an ASP.NET application. A unique instance appears for these counters, named __Total__, which aggregates counters for all applications on a Web server (similar to the global counters described in the first section of this topic). The __Total__ instance is always available. The counters will display zero when no applications are present on the server.

Performance Counter	Description
Anonymous Requests	The number of requests that are using anonymous authentication.
Anonymous Requests/Sec	The number of requests per second that are using anonymous authentication.
Cache Total Entries	The total number of entries in the cache. This counter includes both internal use of the cache by the ASP.NET page framework and external use of the cache through exposed APIs.
Cache Total Hits	The total number of hits from the cache. This counter includes both internal use of the cache by the ASP.NET page framework and external use of the cache through exposed APIs.
Cache Total Misses	The number of failed cache requests per application. This counter includes both internal use of the cache by ASP.NET and external use of the cache through exposed APIs.
Cache Total Hit Ratio	The ratio of hits to misses for the cache. This counter includes both internal use of the cache by ASP.NET and external use of the cache through exposed APIs.
Cache Total Turnover Rate	The number of additions and removals to the total cache per second. It is useful in helping determine how effectively the cache is being used. If the turnover is large, the cache is not being used efficiently.
Cache API Entries	The total number of entries in the application cache.
Cache API Hits	The total number of hits from the cache when it is accessed through only the external cache APIs. This counter does not track any use of the cache internally by ASP.NET.
Cache API Misses	The total number of failed requests to the cache when accessed through the external cache APIs. This counter does not track any use of the cache internally by ASP.NET.
Cache API Hit Ratio	The cache hit-to-miss ratio when accessed through the external cache APIs. This counter does not track any use of the cache internally by ASP.NET.
Cache API Turnover Rate	The number of additions and removals to the cache per second, when used through the external APIs (excluding internal use by the ASP.NET page framework). It is useful in helping determine how effectively the cache is being used. If the turnover is large, then the cache is not being used effectively.
Compilations Total	The total number of compilations that have taken place during the lifetime of the current Web server process. This occurs when a file with an .aspx, .asmx, .ascx, or .ashx extension, or a code-behind source file, is dynamically compiled on the server. Note This number will initially climb to a peak value as requests are made to all parts of an application. Once a compilation occurs, however, the resulting binary is saved to disk, where it is reused until its source file changes. This means that, even in the event of a process restart, the counter can remain at zero (inactive) until the application is modified or redeployed.
Debugging Requests	The number of requests that occur while debugging is enabled.
Errors During Preprocessing	The number of errors that occurred during parsing. Excludes compilation and run-time errors.
Errors During Compilation	The number of errors that occur during dynamic compilation. Excludes parser and run-time errors.
Errors During Execution	The total number of errors that occur during the execution of an HTTP request. Excludes parser and compilation errors.
Errors Unhandled During Execution	The total number of unhandled errors that occur during the execution of HTTP requests. Note An unhandled error is any uncaught run-time exception that escapes user code on the page and enters the ASP.NET internal error-handling logic. Exceptions to this rule occur when: Custom errors are enabled, an error page is defined, or both. The Page_Error event is defined in user code and either the error is cleared (using the HttpServerUtility.ClearError method) or a redirect is performed.
Errors Unhandled During Execution/Sec	The number of unhandled exceptions per second that occur during the execution of HTTP requests.
Errors Total	The total number of errors that occur during the execution of HTTP requests. Includes any parser, compilation, or run-time errors. This counter is the sum of the Errors During Compilation, Errors During Preprocessing, and Errors During Execution counters. A well-functioning Web server should not generate errors. If errors occur in your ASP.NET Web application, they may skew any throughput results because of very different code paths for error recovery. Investigate and fix any bugs in your application before performance testing.
Errors Total/Sec	The number of errors per second that occur during the execution of HTTP requests. Includes any parser, compilation, or run-time errors.
Output Cache Entries	The total number of entries in the output cache.
Output Cache Hits	The total number of requests serviced from the output cache.
Output Cache Misses	The number of failed output-cache requests per application.
Output Cache Hit Ratio	The percentage of total requests serviced from the output cache.
Output Cache Turnover Rate	The number of additions and removals to the output cache per second. If the turnover is large, the cache is not being used effectively.
Pipeline Instance Count	The number of active request pipeline instances for the specified ASP.NET application. Since only one execution thread can run within a pipeline instance, this number gives the maximum number of concurrent requests that are being processed for a given application. In most circumstances it is better for this number be low when under load, which signifies that the CPU is well utilized.
Request Bytes In Total	The total size, in bytes, of all requests.
Request Bytes Out Total	The total size, in bytes, of responses sent to a client. This does not include standard HTTP response headers.
Requests Executing	The number of requests currently executing.
Requests Failed	The total number of failed requests. Any and all status codes greater than or equal to 400 will increment this counter. Note Requests that cause a 401 status code will increment this counter and the Requests Not Authorized counter. Requests that cause a 404 or 414 status code will increment this counter and the Requests Not Found counter. Requests that cause a 500 status code will increment this counter and the Requests Timed Out counter. Note The equivalent ASP counter would also increment on requests rejected, which cannot be done (because the rejection is done by IIS and not the process model).
Requests Not Found	The number of requests that failed because resources were not found (status code 404, 414).
Requests Not Authorized	The number of requests that failed due to no authorization (status code 401).
Requests Succeeded	The number of requests that executed successfully (status code 200).
Requests Timed Out	The number of requests that timed out (status code 500).
Requests Total	The total number of requests since the service was started.
Requests/Sec	The number of requests executed per second. This represents the current throughput of the application. Under constant load, this number should remain within a certain range, barring other server work (such as garbage collection, cache cleanup thread, external server tools, and so on).
Sessions Active	The number of sessions currently active. This counter is supported only with in-memory session state.
Sessions Abandoned	The number of sessions that have been explicitly abandoned. This counter is supported only with in-memory session state.
Sessions Timed Out	The number of sessions that timed out. This counter is supported only with in-memory session state.
Sessions Total	The number of sessions timed out. This counter is supported only with in-memory session state.
Transactions Aborted	The number of transactions aborted.
Transactions Committed	The number of transactions committed.
Transactions Pending	The number of transactions in progress.
Transactions Total	The total number of transactions since the service was started.
Transactions/Sec	The number of transactions started per second.

Related Information

• Overview of ASP.NET Performance Monitoring

• Using the System Monitor (PerfMon) with ASP.NET Applications

• Related Performance Counters