The attached patch makes the following enhancements to the kernel profiler:
- Dynamic allocation of the profile buffer.
This allows for profiling on a production system without the continuous
performance hit that the profiler causes. You can turn it on, get you
data, and then turn it off again....
I submitted this as a patch to 2.3.99pre8, but nobody commented, and it
didn't get applied. I'm resubmitting because the further enhancements
are impractical without this. Control of the buffer is via a
/proc/sys/kernel entry 'prof_shift'. you can write the same value to
this file as you would pass to the profile= parameter at boot time. To
turn off profiling, write a zero to the file. I have a second
implementation of this feature as a system call which I feel is
cleaner, though less practical. Any comments on this matter would be
- Selective profiling by context
This allows the kernel profiler to only be activated when the context
matches the constraints specified in the new files
/proc/sys/kernel/prof_pid and prof_name. The profiler is triggered when
the value in prof_pid equals the pid, or when the value in prof_name
matches the comm entry in the task_struct. If prof_name is NULL
(default) and prof_pid is -1 (default) the profiler acts as usual.
The benefit of this is being able to see what section of the kernel is
effecting the particular task you are trying to optimize.
I also am interested in hearing wether people would like the opposite of
this, i.e. all processes except one specified.... This would be a
simple addition. This would be useful for testing with a client and
server running on the same machine (if this is all you have to work
- Percentage readouts for readprofile
These aren't included in this patch, as it's not directly kernel
related. If anyone wants these they can e-mail me. Basically this adds
a column to the readprofile output that indicates the percentage of
time spent in each area.
Please review and test/apply this patch.
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