DenkzeitWiki

Profiling

PrematureOptimization

JavaSprache
PythonSprache

Java

• JavaTools
  
• http://www.ej-technologies.com/products/jprofiler/overview.html --JProfiler
• http://www.yourkit.com/
• http://ejp.sourceforge.net/ --open source
• http://www.manageability.org/blog/stuff/open-source-profilers-for-java/view --Liste

misc notes

• http://stackoverflow.com/questions/1043817/java-xms-xmx-options-and-speed-trade-off
• http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html
  • It's a good idea to set the minimum and maximum heap size to the same value.
  • In any case, don't let the minimum heap size exceed the maximum heap size.
  
  
• http://www.caucho.com/resin-3.0/performance/jvm-tuning.xtp
  • It is good practice with server-side Java applications like Resin to set the minimum -Xms and maximum -Xmx heap sizes to the same value.
  • For efficient garbage collection, the -Xmn value should be lower than the -Xmx value.
  • If you monitor your java process with an OS tool like top or taskmanager, you may see the amount of memory you use exceed the amount you have specified for -Xmx. -Xmx limits the java heap size, java will allocate memory for other things, including a stack for each thread. It is not unusual for the total memory consumption of the VM to exceed the value of -Xmx.

Python

• http://docs.python.org/lib/profile.html
• http://www.python.org/doc/current/lib/module-hotshot.html
  Nachfolger von profile.py
• http://wingware.com/doc/howtos/performance-profiling-python-code --short intro
• http://webpages.charter.net/erburley/pprofui.html --UI
  
• http://www.onlamp.com/pub/a/python/2005/12/15/profiling.html
  • using hotshot and timeit

user-, sys-, real-time

• http://www.sunmanagers.org/pipermail/summaries/2006-October/007596.html

The user counters show time spent in user mode; the system counters show time spent in system mode.

When operating on user data, a process (or thread) has limited access to other processes, memory, devices, etc. CPU used by such a thread is counted as "user time". If it needs to interact with the system, it makes a kernel or system call (like read()). When the call starts, it has to have extra privileges, so it operates in kernel or system context. Time accumulated by the thread is counted as system time.

• http://stackoverflow.com/questions/556405/what-do-real-user-and-sys-mean-in-the-output-of-time1
  • real - wall-clock-time