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Kernel: Implement a simple process time profiler

The kernel now supports basic profiling of all the threads in a process
by calling profiling_enable(pid_t). You finish the profiling by calling
profiling_disable(pid_t).

This all works by recording thread stacks when the timer interrupt
fires and the current thread is in a process being profiled.
Note that symbolication is deferred until profiling_disable() to avoid
adding more noise than necessary to the profile.

A simple "/bin/profile" command is included here that can be used to
start/stop profiling like so:

    $ profile 10 on
    ... wait ...
    $ profile 10 off

After a profile has been recorded, it can be fetched in /proc/profile

There are various limits (or "bugs") on this mechanism at the moment:

- Only one process can be profiled at a time.
- We allocate 8MB for the samples, if you use more space, things will
  not work, and probably break a bit.
- Things will probably fall apart if the profiled process dies during
  profiling, or while extracing /proc/profile
This commit is contained in:
Andreas Kling 2019-12-11 20:36:56 +01:00
parent adb1870628
commit b32e961a84
13 changed files with 388 additions and 135 deletions

View file

@ -16,4 +16,15 @@ int module_unload(const char* name, size_t name_length)
__RETURN_WITH_ERRNO(rc, rc, -1);
}
int profiling_enable(pid_t pid)
{
int rc = syscall(SC_profiling_enable, pid);
__RETURN_WITH_ERRNO(rc, rc, -1);
}
int profiling_disable(pid_t pid)
{
int rc = syscall(SC_profiling_disable, pid);
__RETURN_WITH_ERRNO(rc, rc, -1);
}
}

View file

@ -41,4 +41,7 @@ __BEGIN_DECLS
int module_load(const char* path, size_t path_length);
int module_unload(const char* name, size_t name_length);
int profiling_enable(pid_t);
int profiling_disable(pid_t);
__END_DECLS