Jee performance tuning existing applications


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  •  XX:SurvivorRatio Survivor Ratio is the ratio of eden to survivor space in the young object section of the heap.  Increasing this setting optimizes the JVM for applications with high object creation and low object preservation.What is CMS garbage collector? The Concurrent (actually mostly concurrent) Mark Sweep (CMS) garbage collector is a non-default old (tenured) generation garbage collector introduced in JVM 1.4 that manages a JVM’s heap by collecting garbage in the old (tenured) generation in a few phases, some of which are concurrent and the others which are stop-the-world. As a consequence of the concurrent phases, this collector minimizes GC pauses and hence is also referred to as the low pause collector [Check24 for further details]How do you enable the CMS Collector?Use the JVM flag -XX:+UseConcMarkSweepGC. When you do this, -XX:+UseParNewGC is implicitly used. However, you may explicitly specify -XX:+UseParNewGC if you wish (but it’s just redundant).Note: You cannot use the default collector or the parallel scavenge collector (-XX:+UseParallelGC) in the Young Generation when using CMS in the old generation. CMS is tightly coupled with ParNewGC in the young generation. ParNewGC is an enhanced version of the parallel scavenge collector that enables GC to be done in the young generation while CMS is in progress in the old generation.Does the CMS Collector require tuning?You’re lucky if the CMS collector gives you optimal performance by just enabling it with -XX:+UseConcMarkSweepGC. Every Hotspot 1.4.2 JVM I’ve come across (enterprise systems), has required some CMS tuning for optimal performance. if tuning your Hotspot 1.4.2 is required, then tuning CMS requires more effort than tuning the default collectors and CMS has a bunch of JVM flags to play around with. Some important JVM flags to consider when tuning CMS are given below:The value set by –XX:CMSInitiatingOccupancyFraction is used as same threshold for both old and permanent generation occupancies. i.e. CMS GC will be initiated in the old and permanent generations when either one of or both the old and permanent generation occupancy exceeds the value of CMSInitiatingOccupancyFraction. This is inconvenient and it implies that you must pay close attention to permanent generation occupancy also and size the permanent generation appropriately.The -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled JVM flags could increase remark pauses, but can contain permanent generation growth (prevent OutOfMemory errors caused by a full permanent generation) and protect against poor GC in old generation (objects in the old generation that are referenced by classes in the permanent generation will not be collected until the classes in the permanent generation are collected).
  • Jee performance tuning existing applications

    1. 1. JEE Performance Tuning : Existing Applications Part 1 © 2011 Fiserv, Inc. or its affiliates.
    2. 2. Agenda • Performance Tuning Roadmap • Understand Performance Objectives • Performance Profiling Tools • Performance Profiling Process • Measuring Performance Metrics • JVM Tuning • Understanding Typical JEE Layered Architectures • Tuning other JEE Layers (JMS, JDBC, Transaction Management) • OS Tuning • App Server Tuning • Best Practices • Performance Checklist2 © 2011 Fiserv, Inc. or its affiliates.
    3. 3. Performance Tuning Roadmap The following sections provide a step wise tuning roadmap. Its also discusses various performance tuning activities like Performance Planning, Profiling, Measurement, Tuning etc3 © 2011 Fiserv, Inc. or its affiliates.
    4. 4. Performance Tuning Roadmap • Understand Performance Objectives - Determine environmental constraints, volume of request, amount of data, configuration of hardware and software etc • Performance Planning -Specify performance targets and benchmarks • Performance Profiling - an activity of collecting performance data from a running application that may be intrusive on application performance responsiveness or throughput • Measure Your Performance Metrics - After you have determined your performance criteria, take measurements of the metrics you will use to quantify your performance objectives. E.g. Monitor Disk and CPU Utilization or Monitor Data Transfers Across the Network. • Performance Analysis – Analyzing existing Profiling results • Locate Bottlenecks in Your System • Performance Tuning - an activity of changing tunable, source code, or configuration attribute(s) for the purposes of improving application responsiveness or throughput • Achieve Performance Objectives4 © 2011 Fiserv, Inc. or its affiliates.
    5. 5. Understand Your Performance Objectives To determine your performance objectives, you need to understand the application deployed and the environmental constraints placed on the system. Gather information about the levels of activity that components of the application are expected to meet, such as: • The anticipated number of users. • The number and size of requests. • The amount of data and its consistency. • Determining your target CPU utilization. • The configuration of hardware and software such as CPU type, disk size vs. disk speed, sufficient memory • The ability to interoperate between domains, use legacy systems, support legacy data. • Development, implementation, and maintenance costs. Footnote (Arial 8pt)5 © 2011 Fiserv, Inc. or its affiliates.
    6. 6. Performance Planning • Specify performance targets and benchmarks, including scaling requirements. Include all user types, such as information-gathering requests and transaction clients, in your benchmarks. Performance requirements should include the required response times for end users, the perceived steady state and peak user loads, the average and peak amount of data transferred per request, and the expected growth in user load over the first or next 12 months. • Create a testing environment that mirrors the expected real-world environment as closely as possible. The only reliable way to determine a systems scalability is to perform load tests in which the volume and characteristics of the anticipated traffic are simulated as realistically as possible. • Load-test the system, find bottlenecks, and eliminate them6 © 2011 Fiserv, Inc. or its affiliates.
    7. 7. Performance Profiling • Performance profiling is an activity of collecting performance data from an operating or running application that may be intrusive on application performance responsiveness or throughput Types of Profilers: 1. Method profiler • Collects information about method execution times • Look for: internal/external method times, frequently • called methods/classes etc. 2. Memory profiler • Collects information about object creation and/or • garbage collection 3. Thread profiler • Looks for thread conflict situations7 © 2011 Fiserv, Inc. or its affiliates.
    8. 8. Profiling Tools • YourKit Java Profiler • JProfiler • HP JMeter • VisualVM (Comes with JDK) • JProbe • NetBeans Profiler (free supported by Oracle) • • JConsole (Java Monitoring and Management Console) • Eclipse Memory Analyzer (MAT) • Eclipse TPTP • Jamon ( • GCViewer( © 2011 Fiserv, Inc. or its affiliates.
    9. 9. Measure Your Performance Metrics • If the aim of the work is to improve the performance in a well-defined benchmark, then the measurement can be well defined. In real life, it may be necessary to design a controlled set of experiments to measure performance on the system being worked on. • You measure the performance, analyze the results, and make changes. This should be iterative process. Applying Change Work Force Performance Enterprise Measurement Application Fluctuations9 © 2011 Fiserv, Inc. or its affiliates.
    10. 10. Performance Metrics - Suggested Measurements • JVM heap size • Total response time • Total server-side service time • DB Layer time • Transaction boundaries • Cache sizes • CPU utilization • Stack traces • GC pauses • Network bandwidth10 © 2011 Fiserv, Inc. or its affiliates.
    11. 11. Heap & CPU Uses Report (Using VisualVM)11 © 2011 Fiserv, Inc. or its affiliates.
    12. 12. Method level View(Using VisualVM)12 © 2011 Fiserv, Inc. or its affiliates.
    13. 13. Performance Optimization Process13 © 2011 Fiserv, Inc. or its affiliates.
    14. 14. Performance Tuning in Depth The following sections talks about various Performance Tuning at different layers like OS tuning, JVM tuning, Integration Layer tuning, Database tuning etc14 © 2011 Fiserv, Inc. or its affiliates.
    15. 15. Understanding Typical JEE Layered Architectures15 © 2011 Fiserv, Inc. or its affiliates.
    16. 16. Performance Tuning Process Enterprise performance problems come from below main areas: • network • databases, • web servers • application servers performance parameters • JVM • Application Architecture/Coding/Design Each area typically causes about a quarter of the performance problems.16 © 2011 Fiserv, Inc. or its affiliates.
    17. 17. Application Classifications • SOA Applications • RIA Web Based Applications • Client Server Application • Standalone applications • Cloud based applications17 © 2011 Fiserv, Inc. or its affiliates.
    18. 18. OS Performance Monitoring • Memory Utilization Attributes of a system’s memory such as paging or swapping activity, locking, and voluntary and involuntary context switching should be monitored, . top command PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2120 testuser 20 0 4373m 15m 7152 S 0 0.2 0:00.10 java • CPU Utilization For an application to reach its highest performance or scalability it needs to not only take full advantage of the CPU cycles available to it but also to utilize them in a manner that is not wasteful. To identify how an application is utilizing CPU cycles, you monitor CPU utilization at the operating system level. CPU utilization on most operating systems is reported in both user CPU utilization and kernel or system (sys) CPU utilization top command top - 16:15:45 up 21 days, 2:27, 3 users, load average: 17.94, 12.30, 5.52 Tasks: 150 total, 26 running, 124 sleeping, 0 stopped, 0 zombie Cpu(s): 87.3% us, 1.2% sy, 0.0% ni, 27.6% id, 0.0% wa, 0.0% hi, 0.0% si Mem: 4039848k total, 3999776k used, 40072k free, 92824k buffers Swap: 2097144k total, 224k used, 2096920k free, 1131652k cached18 © 2011 Fiserv, Inc. or its affiliates.
    19. 19. OS Performance Monitoring Contd • Disk I/O Utilization If an application performs disk operations, disk I/O should be monitored for possible performance issues. Disk I/O utilization is the most useful monitoring statistic for understanding application disk usage since it is a measure of active disk I/O time. iostat -xc • Network Utilization Distributed Java applications may find performance and scalability limited to either network bandwidth or network I/O performance. netstat -i19 © 2011 Fiserv, Inc. or its affiliates.
    20. 20. JVM Tuning20 © 2011 Fiserv, Inc. or its affiliates.
    21. 21. Work Flow of Tuning JVM21 © 2011 Fiserv, Inc. or its affiliates.
    22. 22. 32 bit versus 64 bit Java Runtimes The amount of memory available to the Java Heap and Native Heap for a Java process is limited by the Operating System and hardware. A 32 bit Java process has a 4 GB process address space available shared by the Java Heap, Native Heap and the Operating System. If You need more heap say 8 GB, Then 32 bit JVM would be unfit for this requirement.64 bit processes do not have this limit and the addressability is in terabytes.64 bit Java allows massive Java heaps (benchmark released with heaps upto 200 GB) However the ability to use more memory is not “free”. 64 bit applications also require more memory as java Object references and internal pointers are larger. The same Java application running on a 64 bit Java Runtime may have 70% more footprint as compared to running on a 32 bit Runtime. 64 bit applications also perform slower as more data is manipulated and cache performance is reduced. (As data is larger, processor cache is less effective). 64 bit applications can be upto 20% slower. 64 bit JVM is only recommended if a Java heap much greater than 2 GB is required or application uses computationally intensive algorithms for statistics, encryption etc for high precision support. 32 bit versus 64 bit Runtimes bring another interesting consideration: Scaling. When considering application scaling there are two choices : Monolithic scaling with small number of 64 bit JVMs (scaling up) or Horizontal scaling with many clustered 32 bit JVMs (scaling out).22 © 2011 Fiserv, Inc. or its affiliates.
    23. 23. Recommended GC Monitoring Options GC Command Line Option Most Applicable -XX:+PrintGCTimeStamps -XX:+PrintGCDetails - Minimal set of command line options to enable Xloggc:<filename> for all applications. -XX:PrintGCDateStamps Use when wanting to see a calendar date and time of day rather than a time stamp indicating the number of seconds since the JVM was launched. Requires Java 6 Update 4 or later. -XX:+PrintGCApplicationStoppedTime - Useful when tuning an application for low XX:+PrintGCApplicationConcurrentTime - response time/latency to help distinguish XX:+PrintSafepointStatistics between pause events arising from VM safepoint operations and other sources.23 © 2011 Fiserv, Inc. or its affiliates.
    24. 24. Tuning Garbage Collection with Sun JDK The following example JVM settings are recommended for most engine tier servers: • -server -Xmx1024m -XX:MaxPermSize=128m -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+UseTLAB - XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:CMSIncrementalDutyCycleMin=0 - XX:CMSIncrementalDutyCycle=10 -XX:MaxTenuringThreshold=0 -XX:SurvivorRatio=256 - XX:CMSInitiatingOccupancyFraction=60 -XX:+DisableExplicitGC The above options have the following effect: • -XX:+UseTLAB—Uses thread-local object allocation blocks. This improves concurrency by reducing contention on the shared heap lock. • -XX:+UseParNewGC—Uses a parallel version of the young generation copying collector alongside the concurrent mark-and-sweep collector. This minimizes pauses by using all available CPUs in parallel. The collector is compatible with both the default collector and the Concurrent Mark and Sweep (CMS) collector. • -Xms, -Xmx—Places boundaries on the heap size to increase the predictability of garbage collection. The heap size is limited in replica servers so that even Full GCs do not trigger SIP retransmissions. -Xms sets the starting size to prevent pauses caused by heap expansion. • -XX:MaxTenuringThreshold=0—Makes the full NewSize available to every NewGC cycle, and reduces the pause time by not evaluating tenured objects. Technically, this setting promotes all live objects to the older generation, rather than copying them.24 © 2011 Fiserv, Inc. or its affiliates.
    25. 25. Tuning Garbage Collection with Sun JDK CONTD • -XX:SurvivorRatio=128—Specifies a high survivor ratio, which goes along with the zero tenuring threshold to ensure that little space is reserved for absent survivors. • -XX:+UseConcMarkSweepGC or -J-XX:+UseParNewGC - try these switches if you are having problems with intrusive garbage collection pauses. This switch causes the JVM to use different algorithms for major garbage collection events (also for minor collections, if run on a multiprocessor workstation), ones which do not "stop the world" for the entire garbage collection process. You should also add the line -J-XX:+CMSClassUnloadingEnabled and -J- XX:+CMSPermGenSweepingEnabled to your netbeans.conf file so that class unloading is enabled (it isnt by default when using this collector). • XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing - XX:CMSIncrementalDutyCycleMin=0 -XX:CMSIncrementalDutyCycle=10 The concurrent collector can be used in a mode in which the concurrent phases are done incrementally. Recall that during a concurrent phase the garbage collector thread is using one or more processors. The incremental mode is meant to lessen the impact of long concurrent phases by periodically stopping the concurrent phase to yield back the processor to the application.25 © 2011 Fiserv, Inc. or its affiliates.
    26. 26. Tuning Other Layers & Best Practices26 © 2011 Fiserv, Inc. or its affiliates.
    27. 27. Transaction Management Strategies Transaction Isolation Level Transaction isolation levels are specified to maintain data integrity during concurrent transactions. Usually databases allow for the following transaction isolation level, listed here in decreasing order of performance: • READ_UNCOMMITED allows a transaction to read data that can be changed or removed before the end of another transaction that is writing the data. This offers the best performance since it does not require any serialization, but may lead to dirty and ghost reads. • READ_COMMITED requires that only committed data is read. • REPEATABLE_READ requires that within a transaction, multiple reads of the same entity return the data in the same state. This can be achieved through the use of pessimistic or optimistic locking. In pessimistic locking the corresponding database row is locked, blocking other transactions from accessing the row until the transaction completes. In optimistic locking, no lock is obtained on the entity, but data integrity is maintained through other means, such as version numbers. Stale data is detected if the version number in the database is greater than the version number in memory indicating that the entity’s state was changed by another transaction; at this point the application can roll back its transaction, refresh the state of the entity from the database, and retry the transaction. Due to the cost associated with transaction rollbacks, optimistic locking may not be the best option for highly concurrent applications where the data is modified frequently. An optimistic locking approach may provide better performance for applications where the data is seldom modified • SERIALIZABLE requires that all transactions in a system occur in isolation, as if executed serially. In the pessimistic approach this may require locking a range in a table or a table lock. This offers slowest performance.27 © 2011 Fiserv, Inc. or its affiliates.
    28. 28. Distributed Transaction Tuning XA Two Phase Commit Protocol • A common use of JMS is to consume messages from a queue or topic, process them using a database or EJB, then acknowledge / commit the message. • If you are using more than one resource; e.g. reading a JMS message and writing to a database, you really should use XA - its purpose is to provide atomic transactions for multiple transactional resources. For example there is a small window from when you complete updating the database and your changes are committed up to the point at which you commit/acknowledge the message; if there is a network/hardware/process failure inside that window, the message will be redelivered and you may end up processing duplicates. • As the XA protocol requires multiple syncs to disk to ensure it can always recover properly under every possible failure scenario. This adds significant cost (in terms of latency, performance, resources and complexity). XA protocol needs standard XA complaint Data sources & Adaptors Weblogic : Use Logging Last Resource Optimization When using transactional database applications, consider using the JDBC data source Logging Last Resource (LLR) transaction policy instead of XA. The LLR optimization can significantly improve transaction performance by safely eliminating some of the 2PC XA overhead for database processing, especially for two-phase commit database insert, update, and delete operations.28 © 2011 Fiserv, Inc. or its affiliates.
    29. 29. Tuning JDBC & Database29 © 2011 Fiserv, Inc. or its affiliates.
    30. 30. Tuning JDBC DAO Layer Tuning Options • Connection Pool Sizing and Testing. • Caching Statements. • Connection Pool Request Timeouts. • Recovering Leaked Connection. • PinnedToThread.30 © 2011 Fiserv, Inc. or its affiliates.
    31. 31. Connection Pool Sizing and Testing • Sizing • Initial capacity and Maximum capacity. • Shrink Frequency. • Testing • Test Frequency. • Test Reserved/ Released Connections • Maximum Connections Made Unavailable • Test Table Name31 © 2011 Fiserv, Inc. or its affiliates.
    32. 32. Caching SQL Statements. • Reuses Callable and Prepared Statements in Cache. • Reduces CPU usage at Database side and • Improve performance. • Statement Cache Size • Configured per connection pool. • It cache size for each connection in pool.32 © 2011 Fiserv, Inc. or its affiliates.
    33. 33. Recovering Leaked Connection & Timeout • Leaked Connection • Forcibly reclaims unused connection. • Inactive Connection Timeout. • Connection Request Timeout. • Connection Reserve Timeout. • Maximum number of request that can wait for connection. • PinnedToThread • Pins Connection to ExecuteThread • Connection.close() doesn’t return connection to pool. • Configure initial capacity = maximum capacity. • In most cases, maximum number of connection used does not exceed number of execute threads. • Configure connection refreshing, if database calls fails because of stale connections. • Try to avoid PinnedToThread if database resource is limited.33 © 2011 Fiserv, Inc. or its affiliates.
    34. 34. JMS Tuning • You should get rid of the properties which you dont need and inflate the message. For example, use the setDisableMessageID method on the MessageProducer class to disable message ids if you dont need them. This decreases the size of the message and also avoids the overhead of creating a unique ID. • Also invoking setDisableMessageTimeStamp method on the MessageProducer class disables message timestamps and contributes to making the message smaller. • you should use setTimeToLive, which controls the amount of time (in milliseconds) after which the message expires. By default, the message never expires, so setting the optimal message age, will reduce memory overhead, thus improving performance. • As far as the message body is concerned, you should avoid using messages with a large data section. Verbose formats such as XML take up a lot of space on the wire and performance will suffer as result. Consider usingByteMessages if you need to transfer XML messages to ensure that the message is transmitted efficiently, avoiding unnecessary data conversion. • Also you should be careful with the ObjectMessage type. ObjectMessage is convenient but it comes at a cost: the body of an ObjectMessage uses Java serialization to serialize it to bytes. The Java serialized form of even small objects is very verbose so takes up a lot of space on the wire, also Java serialization is slow compared to custom marshalling techniques. Only use ObjectMessage if you really cant use one of the other message types, for example if you really dont know the type of the payload until runtime. • © 2011 Fiserv, Inc. or its affiliates.
    35. 35. JMS Tuning- CONTD • Another element which influences the performances of your messages is the acknowledge mode: • CLIENT_ACKNOWLEDGE mode is the least feasible option since the JMS server cannot send subsequent messages till it receives an acknowledgement from the client. • AUTO_ACKNOWLEDGE mode follows the policy of delivering the message once-and-only once but this incurs an overhead on the server to maintain this policy and requires an acknowledgement to be sent from the server for each message received on the client. • DUPS_OK_ACKNOWLEDGE mode has a different policy of sending the message more than once thereby reducing the overhead on the server but might impose an overhead on the network traffic by sending the message more than once. • From a performance point of view, usually DUPS_OK_ACKNOWLEDGE gives better performance than AUTO_ACKNOWLEDGE. • Another alternative is to create a transacted session and batch up many acknowledgements with one acknowledge/commit. Other server specific tunings • Tuning the Persistent Store • Tuning App Server JMS Config • Tuning Message Bridge server documentation © 2011 Fiserv, Inc. or its affiliates.
    36. 36. Adding Cache Layer36 © 2011 Fiserv, Inc. or its affiliates.
    37. 37. Best Practices • Only Execute Mandatory Tasks • Increase CPU speed (scale up) • Optimize Algorithm • Exploit Parallelism (Scale Out) • Divide and conquer • Fork-join • Optimize Large Latencies • Best of all world - Do them all • Reduce Use Of XML37 © 2011 Fiserv, Inc. or its affiliates.
    38. 38. Technology based Tuning Long list. I would cover in next session. • Spring • Hibernate • EJB Level Tuning • ESB tools like Mule, Camel, Websphere Message Broker • Tibco EMS/RV • JAXB/XML Beans • JSP/JSP/Servlet • ExtJS/Javascript • Database tuning • JAX-WS and JAX-RS (Web Service) • Cluster tuning • Grid Tuning • OS Tuning • Hardware Tuning/Network tuning (Adding extra bandwidth in network card) • Web Server Tuning38 © 2011 Fiserv, Inc. or its affiliates.
    39. 39. Application Server Tuning 1. Setting Java Parameters for Starting App Server 2. Development vs. Production Mode Default Tuning Values 3. Thread Management 4. Tuning Network I/O 5. Setting Your Compiler Options 6. Using Server Clusters to Improve Performance 7. Monitoring a Server Domain39 © 2011 Fiserv, Inc. or its affiliates.
    40. 40. Sample Server: Weblogic Server Tuning • Uses a platform-optimized, native socket multiplexor. • Uses own socket reader threads and frees up weblogic threads. • Available for most of the Platform Solaris, Linux, HP-UX, AIX, Win • Can be configured using Weblogic Admin Console. • Number of simultaneous operations that can be performed by applications. • Production Mode Default 25 • Tuning criteria. • Request turn around time. • Number of CPUs • % Socket Reader Threads (Default 33%). • In 8.1 Execute Queue can be tuned for Overflow condition • Increases thread count dynamically. • Thread usage can be controlled by creating additional Execute Queues • Performance Optimization for critical application. • Throttle the performance • To protect application from Deadlock • It can have Negative impact on overall performance.40 © 2011 Fiserv, Inc. or its affiliates.
    41. 41. Sample Server: Weblogic Server Tuning • StuckThread Detection • Detects when execute thread can not complete work or accept new work. • Warning purpose only, doesn’t change behavior / state of the thread. • Stuck Thread Max Time , Stuck Thread Timer Interval. • Connection Backlog Buffering. • The number of backlogged TCP connection requests. • Native IO gives better performance, • consider Java IO if NativeIO is not stable. • High number of thread can have negative impact on performance. • More threads does not imply that you can process more work. • Avoid application designs that require creating new threads.41 © 2011 Fiserv, Inc. or its affiliates.
    42. 42. Application Server Tuning : Further Reading 1. Weblogic Server 2. Websphere Server 3. Jboss Server 4. Tomcat Server 5. Glassfish Server © 2011 Fiserv, Inc. or its affiliates.
    43. 43. Performance Checklist • Planning for performance is the single most important indicator of success for a J2EE projects performance. • J2EE profiling needs more than a J2SE profiler—it needs to be J2EE "aware" so J2EE requests can be followed and logged, and communications, sessions, transactions, and bean life cycles can be monitored. • Enterprise performance problems tend to come about equally from four main areas: databases, web servers, application servers, and the network. • Common database problems are insufficient indexing, fragmented databases, out-of-date statistics, and faulty application design. Solutions include tuning the index, compacting the database, updating the database, and rewriting the application so the database server controls the query process. • Common web-server problems are poor design algorithms, incorrect configurations, poorly written code, memory problems, and overloaded CPUs. • Common application-server problems are poor cache management, unoptimized database queries, incorrect software configuration, and poor concurrent handling of client requests. • Common network problems are inadequate bandwidth somewhere along the communication route, and undersized, misconfigured, or incompatible routers, switches, firewalls, and load balancers. • Monitor JVM heap sizes, request response times, request service times, JDBC requests, RMI communications, file descriptors, bean life cycles, transaction boundaries, cache sizes, CPU utilization, stack traces, GC pauses, and network bandwidth.43 © 2011 Fiserv, Inc. or its affiliates.
    44. 44. Performance Checklist- Contd • Watch out for slow response times, excessive database table scans, database deadlocks, unavailable pages, memory leaks, and high CPU usage (consistently over 85%). • Load testing should be repeatable. Tests should include expected peak loads. Tests should be as close to the expected deployed system as possible and should be able to run for a long period of time. • One testing methodology is to determine the maximum acceptable response time page download, estimate the maximum number of simultaneous users, increase simulated users until the application response delay becomes unacceptable, and tune until you reach a good response time for the desired number of users. • Page display should be as fast as possible. Use simple pages with static layouts where possible. Let users get to their destination page quickly. Work with the browsers capabilities. • Use priority queues to provide different levels of service. • Be prepared to handle network congestion and communication failures. • High-performance applications probably need clustering and load balancing. • Close JMS resources when you finish with them. • Start the consumer before the producer.44 © 2011 Fiserv, Inc. or its affiliates.
    45. 45. Performance Checklist- Contd • Separate nontransactional and transactional sessions. • Use nonpersistent messages. • Use shorter or compressed messages. • Tune the redelivery count, the Delivery TimeToLive, and the Delivery capacity. • Use asynchronous processing (MessageListener), parallel processing (ConnectionConsumers and ServerSessionPools), flow control, load-balancing message queues, and duplicate delivery mode (Session.DUPS_OK_ACKNOWLEDGE). Avoid Session.CLIENT_ACKNOWLEDGE. • Use publish-and-subscribe when dealing with many active listeners and point-to-point for only a few active listeners.45 © 2011 Fiserv, Inc. or its affiliates.