[mythtv-users] Random Stuttering
george_mythusers at mari1938.org
Sun Sep 16 19:35:44 UTC 2007
> Hi All,
> I have an issue with my myth system that i'm struggling to get working.
> I have a backend system thats an AMD Semperon 3000+ with 512MB Ram
> 10Gig boot disk and 2x200GB disks for media.
> This has a Dvico DVB card for free to air TV (in australia) and a PVR-500
> for foxtel.
Are your 2x200GB disks IDE or SATA?
> I then have a frontend system thats a Pentium D 2.8Ghz, 1Gb Ram
> The problem i get is that I get random stuttering of video recording. It
> might work fine for 30 mins then 2-3 seconds of stuttering or I might get
> stuttering ever few minutes. It seems random.
> I can't see anything happening out of the ordinary on either system when
> this occurs. the only thing is that if i have a terminal window open on my
> backend system and ping the frontend, during the stutering the ping times
> jump up to over 1000ms for that few seconds - but the terminal windows on
> the box don't freeze or anything like that.
> 64 bytes from 192.168.16.11: icmp_seq=249 ttl=64 time=0.326 ms
> 64 bytes from 192.168.16.11: icmp_seq=250 ttl=64 time=2156 ms
> 64 bytes from 192.168.16.11: icmp_seq=251 ttl=64 time=1156 ms
> 64 bytes from 192.168.16.11: icmp_seq=252 ttl=64 time=156 ms
> 64 bytes from 192.168.16.11: icmp_seq=253 ttl=64 time=0.132 ms
> But pinging other boxes, or pinging the backend from a 3rd box does not do
> I've also tried to play the videos via samba on my windows machine and it
> seems that its the actual videos that have the stuttering in them, not the
> playback, so that makes me think its probably a backend problem, not a
> frontend problem.
> The stutering happens on both high definition and foxtel.
> The backend does not seem to be working too hard:
> top - 13:49:51 up 14:49, 1 user, load average: 0.20, 0.10, 0.06
> Tasks: 58 total, 2 running, 56 sleeping, 0 stopped, 0 zombie
> Cpu(s): 0.3%us, 0.7%sy, 0.0%ni, 96.7%id, 0.7%wa, 1.0%hi, 0.7%si,
> Mem: 451472k total, 446396k used, 5076k free, 1356k buffers
> Swap: 500464k total, 116k used, 500348k free, 356172k cached
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 4569 mythtv 18 0 251m 20m 13m S 0.7 4.7 1:46.77 mythbackend
> 4360 mysql 15 0 140m 29m 4744 S 0.0 6.8 0:04.55 mysqld
> 71 root 10 -5 0 0 0 S 0.0 0.0 0:01.06 kswapd0
> 784 root 21 -4 1908 704 376 S 0.0 0.2 0:00.84 udevd
> 6568 root 23 0 0 0 0 S 0.0 0.0 0:00.55 nfsd
> 6564 root 15 0 0 0 0 S 0.0 0.0 0:00.51 nfsd
> 6565 root 15 0 0 0 0 S 0.0 0.0 0:00.44 nfsd
> I dont' see major conficts for interuppts
> wolverine ~ # cat /proc/interrupts
> 0: 13429809 XT-PIC-XT timer
> 1: 8 XT-PIC-XT i8042
> 2: 0 XT-PIC-XT cascade
> 5: 519423 XT-PIC-XT ivtv0
> 7: 89130 XT-PIC-XT cx88, cx88
> 8: 2 XT-PIC-XT rtc
> 10: 0 XT-PIC-XT ivtv1
> 11: 5155231 XT-PIC-XT sata_via, eth0
> 12: 130 XT-PIC-XT i8042
> 14: 34189 XT-PIC-XT ide0
> 15: 65054 XT-PIC-XT ide1
> NMI: 0
> LOC: 13430083
> ERR: 0
> Any advice or suggestions would be greatly appreciated.
If your media drives are SATA, the fact that your SATA controller shares
an interrupt with your ethernet device might explain your high ping
times during the episodes of stuttering, but may not explain the cause
of the stuttering in the first place. Any other network-intensive
activity happening on your backend during recording? I see it's running
the NFS daemon - any other boxes writing or reading a lot of data to
those drives? If so, you may want to work on separating those two
devices so they do not share an interrupt.
If your media devices are IDE, are you sure DMA is turned on? (See the
What level of logging are doing with mythbackend? I have an
underpowered backend that could not cleanly serve up one video stream to
a remote frontend client with mythbackend running verbose -all logging.
If I turned off all logging, it was fine. I've since upgraded the
disk I/O capabilities of the backend.
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