Samba swamps the server's CPU

[Jeremy Allison]

On Sat, Nov 03, 2001 at 04:17:36AM -0500, Eric P. McCoy wrote:
> Hi.  I'm running Samba 2.2.2 and Linux 2.4.7 on a dual PPro-200/256KB
> server.  The relevant NIC is an Intel EtherExpress PRO/100+.  The
> problem I'm having is that certain programs will swamp the server; the
> load will spike immediately to 50% (i.e., 100% on one CPU) and
> performance will, naturally, bite.  Having another active connection
> to the server at the same time causes _monster_ slowdowns.  I didn't
> think much of this until I ran vmstat and noticed that when I ran one
> of these programs, the context switches per second would jump from
> about 300 to over 10000.  I pulled out strace and this is what I got:
> 
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
>  41.82   12.716340         638     19934           select
>  19.31    5.870802         294     19935           send
>  14.33    4.357302          91     47760           read
>   5.15    1.567179          51     30435           fcntl64
>   5.03    1.530087        9162       167           write
>   4.03    1.226924         201      6110           getdents64
>   2.85    0.867619          40     21692           gettimeofday
>   2.84    0.864095          72     12044      2812 stat64
>   1.55    0.470409          44     10642           _llseek
>   1.12    0.339316          80      4263       192 open
>   0.91    0.276100          45      6190           fstat64
>   0.74    0.226241          55      4084         3 close
>   0.12    0.036709         243       151           ftruncate64
>   0.03    0.009962          39       255           geteuid32
>   0.03    0.009618          38       253           getegid32
> [snipped for brevity]
> ------ ----------- ----------- --------- --------- ----------------
> 100.00   30.407128                184547      3021 total
> 
> I have no idea where to go from here, really.  There's nothing in the
> SMB log.  The client on the other end is a Windows 2000 box (Server,
> but the same thing happens with Pro).  Samba is running as a daemon
> rather than from inetd.
> 
> The odd thing is that 98% of programs work just fine.  (Winamp, most
> noticeably, but I can also copy files and do regular things without
> this problem.)  I'm certain that this problem exists in both 2.2.1 and
> 2.2.2, but I believe that, in some previous version, it didn't exist;
> at least, Alpha Centauri (one of the offending programs) now runs
> unacceptably slowly and it used to work just fine.
> 
> Can anyone point me in the right direction or provide a solution?

Can you test something for me - add the line "kernel oplocks = no"
to the [global] section of the smb.conf. 

Is the slowdown 100% reproducible with certain apps ? If so, a
debug level 10 trace would alsio help.

Thanks,

	Jeremy.