linux-kernel - Re: [2.6.34-rc2 NFS4 oops] open error path failure...

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Message-ID: <y2p6278d2221004020334lfb6513e9w776e33435888f686@mail.gmail.com>
Date:	Fri, 2 Apr 2010 11:34:26 +0100
From:	Daniel J Blueman <daniel.blueman@...il.com>
To:	Chuck Lever <chuck.lever@...cle.com>
Cc:	Trond Myklebust <trond.myklebust@....uio.no>,
	Al Viro <viro@...iv.linux.org.uk>, linux-nfs@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.34-rc2 NFS4 oops] open error path failure...

On Wed, Mar 31, 2010 at 3:21 PM, Chuck Lever <chuck.lever@...cle.com> wrote:
> On 03/31/2010 07:20 AM, Daniel J Blueman wrote:
>>
>> Talking of expensive, I see latencytop show>16000ms latency for
>> writing pages when I have a workload that does large buffered I/O to
>> an otherwise uncongested server. The gigabit network is saturated, and
>> reads often stall for 1000-4000ms (!). Client has the default 16 TCP
>> request slots, and server has 8 nfsds - the server is far from disk or
>> processor-saturated. I'll see if there is any useful debugging I can
>> get about this.
>
> That latency is pretty much guaranteed to be due to a long RPC backlog queue
> on the client.  Bumping the size of the slot table to 128 and increasing the
> number of NFSD threads may help.

Increasing these values did help quite a bit, though I was still
seeing 5000-8000ms at nfs_wait_bit_uninterruptible()  [1] and close().
Then again, I also was seeing 'Scheduler waiting for cpu' taking up to
3000ms! I suspect processor throttling, due to exceeding thermal
limits.

Thanks,
  Daniel

--- [1]

nfs_wait_bit_uninterruptible
nfs_wait_on_request
nfs_wait_in_requests_locked
nfs_sync_mapping_wait
nfs_write_mapping
nfs_wb_nocommit
nfs_getattr
vfs_getattr
vfs_fstat
sys_newfstat
system_call_fastpath
-- 
Daniel J Blueman
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