Re: Link performance over NFS degraded in RHEL5. -- was : Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing

Steve Dickson
2009-06-05T13:33:15Z

Tom Talpey wrote:
> On 6/5/2009 7:35 AM, Steve Dickson wrote:
>> Brian R Cowan wrote:
>>> Trond Myklebust<trond.myklebust@fys.uio.no> wrote on 06/04/2009
>>> 02:04:58
>>> PM:
>>>
>>>> Did you try turning off write gathering on the server (i.e. add the
>>>> 'no_wdelay' export option)? As I said earlier, that forces a delay of
>>>> 10ms per RPC call, which might explain the FILE_SYNC slowness.
>>> Just tried it, this seems to be a very useful workaround as well. The
>>> FILE_SYNC write calls come back in about the same amount of time as the
>>> write+commit pairs... Speeds up building regardless of the network
>>> filesystem (ClearCase MVFS or straight NFS).
>>
>> Does anybody had the history as to why 'no_wdelay' is an
>> export default?
>
> Because "wdelay" is a complete crock?
>
> Adding 10ms to every write RPC only helps if there's a steady
> single-file stream arriving at the server. In most other workloads
> it only slows things down.
>
> The better solution is to continue tuning the clients to issue
> writes in a more sequential and less all-or-nothing fashion.
> There are plenty of other less crock-ful things to do in the
> server, too.
Ok... So do you think removing it as a default would cause
any regressions?

steved.