[Samba] optimizing and scaling ntlm_auth

[Volker Lendecke]

On Tue, Sep 09, 2014 at 06:12:34PM -0400, Louis Munro wrote:
> On 2014-09-09, at 5:52 , Volker Lendecke <Volker.Lendecke at SerNet.DE> wrote:
> >> 
> > 
> > winbind *should* balance between all children, at least we
> > have code to do this. If it does not work, there might be a
> > bug or else it might be that 38 out of 39 children sit in
> > requests that block against the DC. Then only one child is
> > used because it's the only responsive one.
> > 
> > In that situation, can you figure out the call stack of an
> > unused child? Fedora has a "gstack" script that might be
> > helpful here.
> 
> 
> Hi Volcker,
> Here's a stack trace for a process that's idle. 
> The process itself was forked off about 4 days ago and yet it does not seem to be doing anything.
> It still has one connection open to the DC on port 445.
> 
> #gstack 25501
> 
> #0  0x00007f3e66c67218 in poll () from /lib64/libc.so.6
> #1  0x00007f3e69995990 in sys_poll ()
> #2  0x00007f3e699079aa in fork_domain_child ()
> #3  0x00007f3e699087e5 in wb_child_request_trigger ()
> #4  0x00007f3e699cf4ff in tevent_common_loop_immediate ()
> #5  0x00007f3e699cd78c in run_events_poll ()
> #6  0x00007f3e699cdef2 in s3_event_loop_once ()
> #7  0x00007f3e699ce300 in _tevent_loop_once ()
> #8  0x00007f3e698dff03 in main ()
> 
> 
> Does that help?

Yes, it does. This winbind child is really idle. If at the same time
you have multiple ntlm_auth processes asking for attention, we have a
scheduling problem in the winbind parent. Just to make sure: Was this
really under load while one child was busy and ntlm_auth processes were
not being served?

Volker

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