Profile/Systemtap: Difference between revisions

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 If you install from git and from the repositories, in the same system, can have conflicts trying to run the probes.
+=== Adding your user to the needed groups ===
+To run stap as a user, you need add it to the following groups
+ # usermod -a -G stapusr gonzalo
+ # usermod -a -G stapsys gonzalo
+ # usermod -a -G stapdev gonzalo
+after that, you need restart your session.
+You always can run stap as root too.
 === Using systemtap ===
-Systemtap have
+Systemtap have "probes" already included in the kernel, and several libraries in user space too.
+Both GLib and python have probes, making it very useful for us.
+You can use it to monitor when files are read, or when objects are created or destroyed.
+To do it, have a language to create scripts. Several scripts are already created,
+and you can create new or modify them.
+Systemtap monitor events in all the process in the system, but you can define a filter
+to monitor only a specific process.
+This example show how to analyze memory use with SystemTap [http://blog.verbum.org/2011/03/19/analyzing-memory-use-with-systemtap/]
+=== Using with sugar-buid ===
+In sugar-build, we build glib, then we need move the global glib and gobject probes, to not have comflicts.
+I renamed the global probes:
+ # cd /usr/share/systemtap/tapset/
+ # mv 64-glib.stp 64-glib.stp.old
+ # mv 64-gobject.stp 64-gobject.stp.old
+Now we can download a sample test, like [http://people.gnome.org/~walters/glib-memtrace2.stp] and run it in our sugar-build session.
+To attach it to a running process, can use the -x parameter.
+To get the sugar process PID, can do:
+ $ ps ax | grep jarabe
+?        Sl     0:28 python2 -m jarabe.main
+The first number is the PID
+Running stap with the PID we found:
+ $ stap -v -x 24673 glib-memtrace2.stp
+This will show every 5 seconds, the memory use and if GObjects were created.
+Another probe you can use is [[File:Pyfuntime.stp]]
+ $ stap -v -x 24673 pyfuntime.stp
+Will show every time a python method start and finish, and the time spent.
+Finally, to have a "top" like of python functions, download [[File:Pyfuntop.stp]]
+== Troubleshoting ==
+* If your user can't run stap, execute the command "groups" and check if stapusr, stapsys and stapdev groups are present.
+* If you need check what directories is using systemtap to look for the probes, can do:
+ stap -p1 -vv 'probe begin  { }' > /dev/null
 == External links ==
-Analyzing memory use with SystemTap [http://blog.verbum.org/2011/03/19/analyzing-memory-use-with-systemtap/]
+Systemtap wiki https://sourceware.org/systemtap/wiki