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

Steve Malenfant smalenfant at gmail.com
Wed Mar 1 03:37:53 UTC 2006


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.

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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