[Samba] How to profile a samba function

[Michael Wood]

It looks like you fogot to Cc Nikos :)

On 17 October 2013 23:53, Andrew Bartlett <abartlet at samba.org> wrote:

> On Thu, 2013-10-17 at 15:18 +0100, Alex Matthews wrote:
> > 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:
> > http://pastebin.com/98rYXRxe
> >
> > As you can see the only call that takes any 'significant' time is
> > "samba.samba3.smbd.set_nt_acl".
> > 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!
>
> Perf is ideal for this, and has quickly become my favourite profiling
> tool, because it's the first one I've found that I can just pick up and
> use!.  'perf record -g /usr/bin/samba-tool ntacl sysvolreset' and then
> 'perf report -g' will give a lot of really useful output, in particular
> call graphs to isolate not only where the time is spent, but who is
> requesting the time be spent.
>
> I've CC'ed Nikos, who needs help profiling samba-tool dbcheck.  I wonder
> if you could help each other out with the profiling?
>
> Thanks,
>
> Andrew Bartlett
>
> --
> Andrew Bartlett
> http://samba.org/~abartlet/
> Authentication Developer, Samba Team           http://samba.org
> Samba Developer, Catalyst IT                   http://catalyst.net.nz
>
>
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-- 
Michael Wood <esiotrot at gmail.com>