Databases and Information Systems II

Transcription

1 Databases and Information Systems II Performance evaluation Profiling Performance evaluation New compression approach must be competible in terms of Compression ratio Compression time Decompression time Query evaluation time Slow performance can be caused by Slow algorithms Slow implementation 2/14 1

2 Performance evaluation - currenttimemillis() String ret= ""; int runs = 10; int dur = 0; for (int rep = 0; rep < runs; rep++) { long start = System.currentTimeMillis(); for (int i = 0; i < 1000; i++) { ret += i; dur += (System.currentTimeMillis() - start); System.out.println("String: " + (dur/runs) + " ms"); > String: 86 ms > StringBuffer: 0 ms > StringBuilder: 0 ms 3/14 Performance evaluation nanotime() String ret= ""; int runs = 10; int dur = 0; for (int rep = 0; rep < runs; rep++) { long start = System.nanoTime(); for (int i = 0; i < 1000; i++) { ret += i; dur += (System.nanoTime() - start); System.out.println("String: " + (dur/runs) + " ns"); > String: ns > StringBuffer: ns > StringBuilder: ns 4/14 2

3 Wall clock, User, System, and CPU time Wall clock time: Real-world time, while the user waits the system to be finished System.nanoTime(), System.currentTimeMillis() User time: Time spent running the application s code System time: Time spent running OS code caused by your application (e.g. I/O) CPU time: User time + System time; Total time spent using CPU for your application 5/14 Wall clock, User, System, and CPU time Wall clock time: import java.lang.management Real-world time, while the user waits the system to be finished public long getcputime( ) { ThreadMXBean bean = ManagementFactory.getThreadMXBean(); if(bean.iscurrentthreadcputimesupported( )) return bean.getcurrentthreadcputime( ); else User return time: 0L; System.nanoTime(), System.currentTimeMillis() Time spent running the application s code public long getusertime( ) { System time: ThreadMXBean bean = ManagementFactory.getThreadMXBean(); if(bean.iscurrentthreadcputimesupported( )) return bean.getcurrentthreadusertime( ); else CPU return time: 0L; Time spent running OS code caused by your application (e.g. I/O) User time + System time; Total time spent using CPU for your application public long getsystemtime( ) { ThreadMXBean bean = ManagementFactory.getThreadMXBean(); if(bean.iscurrentthreadcputimesupported( )) return (bean.getcurrentthreadcputime( ) - bean.getcurrentthreadusertime( )); else return 0L; 6/14 3

4 Performance evaluation Performance time is influenced by Operating system processes Other processes Tasks of Virtual Machine (e.g. garbage collection) Perform redundant measurements (> 10 runs) System.currentTimeMillis() and System.nanoTime(), CPU, User and System time Simple to use Good for comparing different approaches Not very convenient for finding performance bottlenecks Use Profiler instead 7/14 Profiling A profiler is a performance analysis tool that measures the behavior of a program as it executes, particularly the frequency and duration of function calls. Java Profiler JAMon ( JIP ( TPTP ( 8/14 4

5 Profiling JAMon String ret = ""; Monitor monstring = null; for (int rep = 0; rep < 10; rep++) { MonitorFactory.start("String"); for (int i = 0; i < 1000; i++) { ret += i; monstring.stop(); String html = MonitorFactory.getReport(); Label Hits Avg Total StdDev Last Min Max StringBuffer StringBuilder String /14 Profiling JAMon Advantages Convenient to use Independent of platform and IDE Any granularity Especially easy to use for web and database applications Disadvantages Needs changes in program code 10/14 5

6 Profiling JIP (Java Interactive Profiler) > java javaagent:path/profiler.jar Main Thread: Time Percent Count Total Net Total Net Location ===== ===== === ===== === ========= 1 457,6 5,5 100,0 1,2 +--Main:main () 1 446,1 446,1 97,5 97,5 +--Main:testString () 1 5,2 5,2 1,1 1,1 +--Main:testStringBuffer () 1 0,7 0,7 0,2 0,2 +--Main:testStringBuilder () 11/14 Profiling JIP (Java Interactive Profiler) Advantages Easy to use Efficient to use Independent of platform and IDE Disadvantages Not very convenient to analyze the results Finest granularity: Methods 12/14 6

7 Profiling TPTP Eclipse Menu Run Profile Configurations 13/14 Profiling TPTP Advantages Convenient to use No changes in program code GUI allows detailed analysis Disadvantages Eclipse plugin (dependent on Eclipse) Finest granularity: Methods 14/14 7