[Samba] Winbind process stuck at 100% after changing use_mmap to no

[Jeremy Allison]

On Fri, Jul 01, 2016 at 10:00:21AM +0100, Alex Crow wrote:
> Hi,
> 
> We've had a strange issue after following the recommendations at
> https://wiki.samba.org/index.php/Ping_pong, particularly the part
> about mmap coherence. We are running CTDB/Samba over a MooseFS
> clustered FS, and we'd not done the ping-pong before. After finding
> that the mmap coherence test did not pass, we changed "use mmap" to
> "no" in smb.conf.
> 
> This morning as users began to access their drives and profiles,
> performance tanked to such a degree that most people could not
> complete loading profiles and even where successful, windows drive
> mappings were taking minutes to complete per share.
> 
> When looking at the active CTDB servers, on each a single Winbindd
> process was taking up 100% of CPU. After reverting the "use_mmap" to
> yes, performance returned completely to normal.
> 
> We found this very odd as this is a recommended setting according to
> the page above.

Hmmm. I know very little about MooseFS. Did you get an strace
on the winbindd process to try and figure out what it was doing ?