[Samba] How to profile a samba function

Alex Matthews qoole.samba at lillimoth.com
Thu Oct 17 08:18:11 MDT 2013

Hi all,

I am trying to track down what is causing the slow running of 
sysvolreset on my system.
I am aware that I have a great deal of files in my 'netlogon' directory 
which is why the problem is so apparent for me.

sysvolreset takes approx 5+ minutes to complete.

Tracing out samba-tool shows that the slowdown is caused by the samba 
function 'set_nt_acl'.
This function takes approx 120ms to run, which when multiplied up by a 
few thousand files (2,000 in my case) you very quickly end up in minutes.

running samba-tool using cProfile ('python2.7 -m cProfile 
/usr/bin/samba-tool ntacl sysvolreset') gives the following results: 

As you can see the only call that takes any 'significant' time is 
Because this function is part of the samba source rather than part of a 
python script cProfile cannot profile any further.
How can I profile this function in smbd (without having to recompile 
samba would be ideal).
I've seen 'perf' mentioned in other threads, is there any way this tool 
can be used?
If I have to recompile and add my own timing code I will, but only 
really as a last resort.

This problem can't be isolated to just sysvolreset as the 'set_nt_acl' 
function must be called quite frequently elsewhere.
I think 120ms for a call to return is quite a long time. I would expect 
to see an overall performance gain if it can be optimised a bit!



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