waiting on sbwait

[Danny Braniss]

> 
> > Danny Braniss wrote:
> > 
> > >Hi,
> > >	We have a host running samba under -stable 4.10, and quiet frequently
> > >it becomes uresponsive, hitting ^T gives 
> > >
> > >load: 0.00  cmd: ls 12807 [sbwait] 0.00u 0.00s 0% 160k
> > >
> > >so my guess is that we are running out of some resource (socket buffer).
> > >
> > >so, if this is true, is there some sysctl to increase?
> > >
> > >danny
> 
> > I'm not sure if it's what you're hitting, but Perhaps the sysctl 
> > "kern.ipc.maxsockets" needs to be raised, though it seems like you'd 
> > need a decent amount of concurrent active sessions to reach this 
> > ceiling. Also it's read-only, so you'll want to tune it in loader.conf.
> > 
> > -mpf
> > 
> 
> sometimes we get 
> load: 0.04  cmd: dmesg 13453 [nfsrcvlk] 0.00u 0.00s 0% 148k
> 
> and looking through the code, there might be some connection between sbwait
> and nfsrcvlk, but i doubt that it's sockets that im running out off, neither
> mbufs, since:
> 
> foundation> netstat -m
> 326/1216/26624 mbufs in use (current/peak/max):
>         326 mbufs allocated to data
> 321/428/6656 mbuf clusters in use (current/peak/max)
> 1160 Kbytes allocated to network (5% of mb_map in use)
> 0 requests for memory denied
> 0 requests for memory delayed
> 0 calls to protocol drain routines
> 
> also, the process enters sbwait either in sosend or soreceive, make me
> believe that it's some resource, rather than data, that is missing.
> 
> the fact that this 'unresponsivness' happens sometimes is making this
> rather challenging, but try to tell this to the users :-)
> 
> danny

found the cause: NFS/amd
a user had several symlinks to /net/host/xyz, and host was down.
doing ls -F /net/host/xyz does the trick, the machine becomes
unresponsive.

now have to look for the reason :-(

danny