Re: high load, no bottleneck

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

On Sep 17, 2013, at 5:39 PM, Emmanuel Dreyfus <manu%netbsd.org@localhost> wrote:

> 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

What are your clients doing?

Which vnode(s) are your nfsd threads waiting on (first arg to vn_lock)?

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)