CIT 668: System Architecture

Performance Testing Topics

1. What is performance testing? 2. Performance-testing activities 3. UNIX monitoring tools What is performance testing?

Performance testing is a type of testing intended to determine the responsiveness, throughput, reliability, and/or scalability of a system under a given workload. - http://perftestingguide.codeplex.com/

Performance testing goals: – Assess production readiness – Evaluate against performance criteria – Compare performance characteristics of multiple systems or system configurations – Find the source of performance problems – Support system tuning – Find throughput levels Performance Testing Activities

http://perftestingguide.codeplex.com/ Testing Types Performance testing: determining performance, scalability, or stability characteristics of system; a superset of the other testing types.

Load testing: determining performance characteristics of system when subjected to work load expected during production.

Stress testing: determining performance characteristics of system when subjected to work loads beyond those expected during production to determine under what conditions system will fail.

Baselines

A baseline is a set of data used for comparison.

In performance testing, baselines are used to evaluate the effectiveness of subsequent performance-improving changes to the system.

Once the system has been changed, a new baseline must be measured. Benchmarking

Benchmarking is the process of measuring system performance using standard tests and comparing it against a well known system.

SPEC CPU2006 (SPECint, SPECfp) SPEC power2008 (power usage) BogoMips SPEC sfs2008 (NFS, CIFS) Dhrystone SPEC virt2010 (virtualization) Whetstone SPEC web2005 (PHP or JSP)

Weighted TeraFLOPS

NAS Parallel Benchmarks Experimenter Effect

Monitoring the system affects performance. Monitoring tools use system resources. If you’ve consistently monitored system, then monitoring won’t alter system performance. Identify Bottlenecks

Identify which aspect of performance Latency: delay until initial access. Throughput: rate of transfer/processing. Identify which system component CPU Memory Disk Network Performance Problem Solutions

1. Get more of needed resource. Ex: Upgrade processor, use striped disk array. 2. Reduce system requirements. Ex: Kill processes, move services to other hosts. 3. Eliminate inefficiency and waste. Ex: Produce a static home page every 15 minutes instead of regenerating each access. 4. Ration resource usage. Ex: Set process priorities with renice. Ex: Limit process resource usage with limit. Performance Testing Services

• Gomez • Keynote • Pingdom • SiteUptime • Alertra Performance Testing Activities Activities

Activity Input Output Identify test environment Production system Comparison of test and architecture production environments Test system architecture Environment concerns Available tools Are other tools needed? ID acceptance criteria Client expectations Success criteria Risks to be mitigated Performance goals and requirements Plan and design tests Available system features Test data to implement and components tests Use cases Use models to be simulated Success criteria Resources required Configure test environment Tools Configured load generation and resource monitoring tools Tests Environment ready for tests Activities

Activity Input Output Implement test design Configured tools Validated, executable tests Prepared environment Validated resource monitoring Available tools Validated data collection Execute tests Test execution plan Test results Configured tools Executable tests Analyze Results, Report, Test results Results analysis and Retest Acceptance criteria Recommendations Risks, concerns, and issues Reports Web Load Tools

• ab (Apache Bench) • httperf • autobench (httperf multihost wrapper) • JMeter • openload • SIEGE Metric Collection and Notification Tools

• Ganglia • Cacti • Nagios • Zabbix • Hyperic HQ • Munin • ZenOSS • OpenNMS • GroundWork • Monit

UNIX Monitoring Tools Monitoring Processes uptime Provides aggregate data about system load. ps Shows running processes with CPU, mem usage. top Updated list of running processes + summaries. vmstat Summary data about processes and CPU usage. Uptime Uptime provides the following data How long system has been running. Number of users logged in. Average number of runnable processes. In last 1, 5, 15 minutes. Want a load average under 3. Uptime example > uptime 17:40 up 126 days, 8:03, 6 users, load average: 1.40, 1.03, 0.55 vmstat

• Number of Runnable and Blocked processes. • Memory (virtual, free, buffered, cached) • Blocks/second transferred in (bi) and out (bo) • Interrupts/sec (in) and context switches/sec (cs) • CPU usage by user, system, idle, and waiting.

> vmstat 5 4 procs ------memory------swap------io------system------cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 395716 45176 211284 88480 0 0 1 2 1 2 9 3 88 0 0 0 395716 45168 211300 88480 0 0 0 50 1035 1677 0 0 100 0 0 0 395716 45168 211300 88480 0 0 0 0 1040 1670 0 0 99 0 0 0 395716 45168 211300 88480 0 0 0 0 1033 1660 0 0 100 0

Identifying CPU Shortages

1. Short-term CPU spikes are normal. 2. Consistently high number of runnable processes (r) in vmstat. 3. Consistent high total CPU usage (sy+us). 4. High system time compared to user time and high context switches indicates system is thrashing between processes instead of doing user work.

Changing Process Priorities

Nice values Positive values lower priorities. Negative values increase priorities. If you know a process will be a CPU hog, nice +5 command_name If you detect a CPU hog after it’s started, renice 5 PID Managing Processes with kill TERM (default) Terminates process execution (Ctrl-c). Processes can catch or ignore signal. KILL (9) Terminates process execution. Processes cannot catch or ignore. Processes waiting on I/O will not die. STOP Suspends process execution until SIGCONT (Ctrl-z). Useful for moving CPU hog out of way temporarily. Imposing Limits on Processes

CPU time ulimit –t secs Maximum file size ulimit –f KB Maximum data segment ulimit –d KB Maximum stack size ulimit –s KB Maximum physical mem ulimit –m KB Maximum core size ulimit –c KB Maximum number procs ulimit –u n Maximum virtual mem ulimit –v KB Monitoring Memory

Use free to see how memory is used. System will use most free memory for caching. System will swap out inactive processes. Don’t worry until free < 5% of total memory. Use vmstat to detect paging activity. Page out (so) rate greater than 0 consistently. High page in (si) rate, as system uses the paging facility to load programs into memory.

Managing Memory

1. Improving paging capacity. Add new swapfiles with swapon. Add new swap partitions. 2. Improving paging performance. Use swap partitions instead of swap files. Distribute swap resources across disks. 3. Migrate memory hogs to another host. 4. Add more memory. Monitoring Disk I/O

Use iostat to get per disk statistics. Transactions per second (tps). Blocks read/written per second. Managing disk performance problems. Distribute heavily used data across disks/ctrlers. Get more or faster disks. Use RAID or LVM striping. iostat

> iostat 2 Linux 2.6.15-23-386 (zim) 03/26/2007 avg-cpu: %user %nice %system %iowait %steal %idle 8.55 0.18 3.22 0.09 0.00 87.96

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn hde 0.69 8.18 9.43 89783416 103565744 hdh 0.15 1.33 3.37 14590831 36969599 hdc 0.00 0.00 0.00 9548 0 avg-cpu: %user %nice %system %iowait %steal %idle 0.17 0.00 0.17 0.00 0.00 99.67

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn hde 0.33 0.00 21.33 0 128 hdh 0.00 0.00 0.00 0 0 hdc 0.00 0.00 0.00 0 0

Managing Disk Capacity

Detecting disk resource usage. List all partition usage with df –h Identify high usage directories with du Summary data: du –s Highest usage directories: du -k /|sort –rn Use find to detect disk hogs. Use find –size to search for big files. Use –atime +X to identify files that haven’t been used in X days. Managing Disk Shortages

1. Add more disks. 2. Move files to remote fileservers. 3. Eliminate unnecessary files. 4. Compress large infrequently used files. 5. Impose disk quotas on users. Soft limit: can be violated temporarily. Hard limit: cannot be violated.

Monitoring Network Connections

List listening network ports lsof -i List firewall rules (which ports are accessible) iptables -L List network connections and listening ports netstat -anp IPTraf

CIT 470: Advanced Network and System Administration Slide #32 Managing Network Capacity

1. Move applications onto separate servers. 2. Add more NICs and bond them. 3. Upgrade from 1Gbps to 10Gbps Ethernet if supported by server hardware. Key Points Performance testing terms – Load testing and stress testing – Latency and throughput – Baselines and benchmarks Performance testing activities 1. Identify test environment 2. Identify performance criteria 3. Plan and design tests 4. Configure test environment 5. Implement test design 6. Execute tests 7. Analyze results, report, and retest References 1. Mark Burgess, Principles of System and Network Administration, Wiley, 2000. 2. Aeleen Frisch, Essential System Administration, 3rd edition, O’Reilly, 2002. 3. Mike Loukides and Gian-Paolo D. Musumeci, System Performance Tuning, 2nd edition, O’Reilly, 2003. 4. Evi Nemeth et al, UNIX System Administration Handbook, 3rd edition, Prentice Hall, 2001. 5. patterns & practices, Performance Testing Guidance for Web Applications, http://perftestingguide.codeplex.com/