[mythtv-users] IOBOUND error over cifs (to nslu2)

[Brian Wood]

On Feb 28, 2006, at 8:37 PM, Steve Malenfant wrote:

> WA is always using most of the CPU time...
>
> procs -----------memory---------- ---swap-- -----io---- --system--  
> ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs  
> us sy id wa
>  0  2    148  15012  20464 863052    0    0     0   216 3464  3993   
> 4  7  0 89
>  1  2    148  15012  20464 863052    0    0     0     0 3140  3462   
> 0  1  0 99
>  0  2    148  14996  20440 863108    0    0     0   208 3397  3688   
> 3  7  0 90
>  0  2    148  14968  20440 863108    0    0     0    16 3481  3695   
> 1  6  0 93
>  0  2    148  15036  20456 862996    0    0     0   208 3460  3758   
> 4  6  0 90
>
> Now I'm getting these nice messages :
> 2006-02-28 22:28:18.104 DevRdB(0) Error: Driver buffers overflowed
>
> I guess I can't use the NSLU2 for recording.  What I usually do is
> move the files I won't watch for a while on it, cause reading is fine.

What software/firmware are you using on the slug (NSLU2)? The stock  
Linksys firmware is not optimum as far as performance is concerned.  
Also, have you "de-underclocked" your slug? The CPU is in fact a  
266Mhz. chip, which Linksys has for some strange reason throttled  
down to 133. By removing one resistor you can get the speed back to  
266 for a bit of a performance boost.

Check out :
http://groups.yahoo.com/group/nslu2-linux/

For several options to the stock firmware, including a Debian port.  
There is also some information on optimizing performance as well as  
recording video. You might also be able to use NFS instead of samba  
for a bit of help as well.

I apologize if you were already aware of these options. I'm running  
several slugs, one as a mail server and another as a (somewhat slow)  
Apache box. It's a lot of machine for $90.

>
> Some high WA happens as well I try to watch 1 program and record 2
> programs at once on my backend.  Poor 1.6 Ghz server can't handle 50
> mbits recording/playing, but handles ftp at 400 mbits...
>
> Steve M.
>
> On 2/28/06, Brandon Stoll <mrmagoo at mrmagoo.org> wrote:
>> On 2/28/06, Steve Malenfant <smalenfant at gmail.com> wrote:
>>> I have a frontend and a backend.  My backend has 2 HD tuner that
>>> record on the local disk, that works just fine.
>>>
>>> My frontend has been transformed into slave backend, it has 1 HD  
>>> tuner
>>> in it.  I want to use it to record an extra program.  The problem is
>>> that I get IOBOUND error to the backend and that my frontend has  
>>> only
>>> a small 10G partition for linux (bad choice, I know).
>>>
>>> So I'm using my nslu2 mounted with cifs : //nslu2//public on
>>> /mnt/nslu2 type cifs (rw,mand)
>>>
>>> While I'm recording an HD program, top shows this :
>>>
>>> Cpu(s):  0.3% us,  3.0% sy,  0.0% ni,  0.0% id, 94.7% wa,  2.0%  
>>> hi,  0.0% si
>>>
>>> I've got a few errors in my log that looks like this :
>>> 2006-02-28 18:54:33.218 TFW, Error: Write() -- IOBOUND begin cnt 
>>> (9400) free(555)
>>> 2006-02-28 18:54:33.221 TFW, Error: Write() -- IOBOUND end
>>> 2006-02-28 18:54:33.315 TFW, Error: Write() -- IOBOUND begin cnt 
>>> (9400)
>>> free(3123)
>>> 2006-02-28 18:54:33.321 TFW, Error: Write() -- IOBOUND end
>>>
>>> They lasted only for 4 seconds and the rest of the recording  
>>> seems to
>>> have recorded just fine.
>>>
>>> I'm not sure that I would be able to use the frontend while I'm
>>> recording.  I know the nslu2 isn't fast, although it can handle at
>>> least 40 mbits/sec.
>>>
>>> Anybody knows why the "WA" is so high?
>>> A larger ring buffer would help here?
>>>
>>> Thanks.
>>>
>>> Steve M.
>>
>>
>> Have you tried increasing/decreasing the "HD Ringbuffer" setting in
>> the general settings (all backends have to be restarted if you change
>> this I believe)?  Also make sure the nics are at 100mb/full-duplex
>> (ethtool).
>>
>> running `vmstat 1` should give you a little bit better information on
>> resource usage.  The WA is how much time is being spent waiting for
>> disk read/writes.  Increasing the buffer size isn't going to help you
>> if you are seeing high WA times for the whole recording.
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