Re: Slow NFS loop performance.

["dE ." <de.techno@gmail.com>]

On 11/26/12 21:38, J. Bruce Fields wrote:
> On Mon, Nov 26, 2012 at 09:28:06PM +0530, dE . wrote:
>> On 11/23/12 22:53, J. Bruce Fields wrote:
>>> On Fri, Nov 23, 2012 at 04:31:55PM +0530, dE . wrote:
>>>> Humm... The last thing I expected was no response even in the mailing list.
>>>>
>>>> So I'm filing a bug on this.
>>>>
>>>> On Oct 23, 2012 2:19 PM, "dE ."<de.techno@gmail.com>   wrote:
>>>>> Hi!
>>>>>
>>>>> Great job with NFS server, it surely is fast, but not on loop devices.
>>>>>
>>>>> If I loop mount a file and share the mount point over NFS3 or NFS4, the
>>>>> write performance of the client on the loop mounted share is pretty bad.
>>>>>
>>>>> On a 100 Mbps (or 12.5MBps) full duplex Ethernet link, I get ~8MBps
>>>>> speeds, whereas on the loop mounted device, I get at best 6MBps.
>>> What exactly is your test?
>>>
>>> --b.
>> Sorry for the late response. I'd 200+ unread mails.
>>
>> I'm writing a large file to the mounted loop device.
> How large, and do you have the exact command you're using for that?
>
> Also, what are the client and server versions?
>
> I don't have any good idea off the top of my head.  I doubt anyone's
> worked on optimizing exports of loop devices.  I guess the first step
> would be to collect some statistics in the two cases (loop device and
> non-loop device), compare them, and see if you can see any patterns.
> /proc/self/mountstats on the client, and /proc/fs/nfsd/pool_stats, on
> the server, would be starting points.  Maybe perf on the server could
> also show up something.  Just running "top" on the server might be
> interesting.  (E.g.  is the CPU obviously busier in the slow case?)
>
> --b.

I'll try it out, but I've see no CPU usage problem here. This time I'll 
use dd (I did that previously also).