Is your profiler speaking the same language as you? -- Docklands JUG
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Profilers are absolute beasts. And profilers might prove useful to pinpoint the performance issues in your Java applications. By using profilers, developers are fortunate to find the root cause of an issue at hand. However, it requires effort to actually comprehend the data collected by the profiler. Due to the inherent complexity of the data, one has to understand how this data is collected. And thus understand how the profiler actually works. During this talk we will go through the classic profiler features. What is a hotspot? What is the difference between sampling and instrumentation from the profiler point of view? What are the problems with either of those methods? What is the time budget of the application? And more! I will also showcase a new kid on the block among the profiling tools: XRebel. This tool provides insight into application behaviour and permits the developers to discover application level issues.
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Is your profiler speaking the same language as you? -- Docklands JUG
- 1. Is your profiler speaking the same language as you? Simon Maple @sjmaple
- 3. Agenda • Performance Tools • Performance by numbers • Sampling vs Tracing • XRebel • JRebel 3
- 5. Performance Tools • Java Monitoring Tools • Java Profilers • Java Testing Tools 5
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- 16. The Journey of Performance 16
- 20. Profiling CPU Tracing Sampling Memory Usage Allocation We are only talking about this part today
- 21. JVM has ability to produce thread dump: Press Ctrl+Break on Windows kill -3 PID on *nix "http-nio-8080-exec-1"#40 daemon prio=5 os_prio=31 tid=0x00007fd7057ed800 nid=0x7313 runnable java.lang.Thread.State: RUNNABLE at o.s.s.p.w.OwnerController.processFindForm(OwnerController.java:89) at s.r.NativeMethodAccessorImpl.invoke0(Native Method) at s.r.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at s.r.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at j.l.r.Method.invoke(Method.java:497) What is a sample?
- 22. Sampling interval : 20 ms Sample count: 4
- 23. Sampling interval : 1 ms Sample count: 100+
- 27. Taming safepoint bias Java Mission Control Proprietary protocol Java 7u40 Honest Profiler https://github.com/RichardWarburton/honest-profiler AsyncGetCallTrace JVMTI NB! not documented
- 28. public void businessMethod() { long start = System.currentTimeMillis(); work(); Profiler.log(System.currentTimeMillis()-‐start); } Tracing (Instrumentation)
- 29. Tracing public void businessMethod() { long start = System.nanoTime(); work(); Profiler.log(System.nanoTime()-‐start); }
- 30. Tracing public void businessMethod() { Profiler.start(“businessMethod"); try { work(); } finally { Profiler.log("businessMethod"); } }
- 31. System.nanoTime System.currentTimeMillis Parallel thread updating easily accessible memory location sleep-wakeup-update yield-wakeup-update busy-loop-update
- 32. class Profiler { Loop loop; public static void start(String method) { long now = loop.getTime(); … }
- 33. public class Loop implements Runnable { private volatile long time; public void run() { while (running) { time = System.nanoTime(); sleep(); } } public final long getTime() { return time; } Busy Loop
- 34. Nano seconds put into perspective Reading memory is not free. It takes cycles = nanoseconds Each (software) layer is not free. JVM,JNI,OS,HW http://shipilev.net/blog/2014/nanotrusting-nanotime/ Nanotrusting the NanoTime
- 35. Nano seconds put into perspective http://shipilev.net/blog/2014/nanotrusting-nanotime/ Nanotrusting the NanoTime granularity_nanotime: 26.300 +-0.205 ns latency_nanotime: 25.542 +-0.024 ns granularity_nanotime: 29.322 +-1.293 ns latency_nanotime: 29.910 +-1.626 ns granularity_nanotime: 371,419 +-1,541 ns latency_nanotime: 14,415 +-0,389 ns Linux Solaris Windows
- 36. Sleep timer: time-slicing & scheduling Minimum sleep times: Win8: 1.7 ms (1.0 ms using JNI + socket poll) Linux: 0.1 ms OS X: 0.05 ms VirtualBox + Linux: don’t ask :) Still uses 25-50% of CPU core Yield? Windows scheduler skips yielded threads in case of CPU starvation
- 37. public class Loop implements Runnable { private volatile long time; public void run() { while (running) { time = System.nanoTime(); sleep(); } } private void sleep() { if (!MiscUtil.isWindows()) { Thread.yield(); } } Busy Loop
- 38. public class Loop implements Runnable { private volatile long time; public void run() { while (running) { time = System.nanoTime(); sleep(); } } private void sleep() { if (!MiscUtil.isWindows()) { Thread.yield(); } } Busy Loop
- 39. Busy Loop public class Loop implements Runnable { private volatile long time; public void run() { while (running) { time = System.nanoTime(); sleep(); } } private void sleep() { if (!MiscUtil.isWindows()) { Thread.yield(); } }
- 40. public class Loop implements Runnable { private volatile long time; public void run() { while (running) { time = System.nanoTime(); sleep(); } } private void sleep() { if (!MiscUtil.isWindows()) { Thread.yield(); } } Busy Loop
- 41. main() foo() bar() baz() Tracing relatively higher overhead for fast methods :(
- 42. Database access Web Services RMI Various application layers 3rd-party components HTTP session Exceptions Caches File system access View rendering Serialization GC What other performance considerations should we have?
- 43. Questions you should be asking …….. …….. …….. ……..
- 44. Questions you should be asking Where was most of the time spent? How many SQL queries were executed? How much time did the external calls take? What’s my HTTP session state? Is caching working properly? Is there any excessive work done by the app?
- 45. Most improvement gained here! This is where we should focus first! A B C D E
- 47. Download trials and get FREE shirts :) JRebel: http://0t.ee/docklandsjr XRebel: http://0t.ee/docklandsxr 47