Re: high load, no bottleneck

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

I was suggested this should be better posted on tech-kern. It happened
on NetBSD-6.0, and I tried to upgrade the kernel to -current, with the
same result.

On Tue, Sep 17, 2013 at 12:54:59PM +0000, Emmanuel Dreyfus wrote:
> I have a NFS server that exhibit a high load (20-30) when supporting
> about 30 clients, while there is no apparent bottleneck: low disck 
> activity, CPU idle most of the time, plenty of available RAM.
> 
> Of course service is crapy, with many timouts. Any hint of what can be
> going on?

I found the bottleneck. ps does not show it because it happens within
the differen threads of nfsd.  DDB tells me that almost all nfsd threads 
are waiting on tstile with this backtrace:

turnstile_block
rw_vector_enter
genfs_lock
VOP_LOCK
vn_lock
vget
ufs_ihashget
ffs_vget
ufs_fhtovp
VFS_FHTOVP
nfsrv_fhtovp
nfsrv_write
nfssvc_nfsd
sys_nfssvc


-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost