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

[Alex Crow]

On 02/07/16 10:29, Alex Crow wrote:
> On 01/07/16 19:28, Jeremy Allison wrote:
>> 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 ?
> I'm afraid not, the priority was to get people working and I was fixing
> it remotely.
>
> I may be able to try it on a test setup.
>
> Thanks
>
> Alex

Here's the end of the winbindd process, this time on logoff:

fcntl(25, F_SETLKW, {type=F_UNLCK, whence=SEEK_SET, start=8, len=1}) = 0
open("/etc/group", O_RDONLY|O_CLOEXEC)  = 34
fstat(34, {st_mode=S_IFREG|0644, st_size=963, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x7f6e2ca09000
read(34, "root:x:0:\nbin:x:1:\ndaemon:x:2:\ns"..., 4096) = 963
read(34, "", 4096)                      = 0
close(34)                               = 0
munmap(0x7f6e2ca09000, 4096)            = 0
socket(PF_LOCAL, SOCK_STREAM, 0)        = 34
fcntl(34, F_GETFL)                      = 0x2 (flags O_RDWR)
fcntl(34, F_SETFD, FD_CLOEXEC|0x2)      = 0
connect(34, {sa_family=AF_LOCAL, sun_path="/var/run/nslcd/socket"}, 23) = 0
poll([{fd=34, events=POLLOUT}], 1, 10000) = 1 ([{fd=34, revents=POLLOUT}])
sendto(34, "\1\0\0\0\212\23\0\0\257&\0\0", 12, MSG_NOSIGNAL, NULL, 0) = 12
poll([{fd=34, events=POLLIN}], 1, 60000) = 1 ([{fd=34, 
revents=POLLIN|POLLHUP}])
read(34, "\1\0\0\0\212\23\0\0\3\0\0\0", 1024) = 12
close(34)                               = 0
fcntl(28, F_SETLKW, {type=F_RDLCK, whence=SEEK_SET, start=232, len=1}) = 0
fcntl(28, F_SETLKW, {type=F_UNLCK, whence=SEEK_SET, start=232, len=1}) = 0
fcntl(32, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=48, len=1}) = 0
fcntl(32, F_SETLKW, {type=F_UNLCK, whence=SEEK_SET, start=48, len=1}) = 0
writev(33, 
[{"\264\r\0\0\2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 
3496}, {"\0\0\0\0\0\0\0\0s\0\0\300", 12}], 2) = -1 EPIPE (Broken pipe)
--- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=31971, si_uid=0} ---
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=3661, ...}) = 0
geteuid()                               = 0
write(16, "[2016/07/02 15:12:16.209453,  0]"..., 95) = 95
geteuid()                               = 0
write(16, "  Could not write result\n", 25) = 25
close(11)                               = 0
close(35)                               = 0
exit_group(1)                           = ?


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