[mythtv-users] MythTV performance in a demanding real-life environment

Yeechang Lee ylee at pobox.com
Mon Apr 9 07:18:43 UTC 2007


Michael T. Dean <mtdean at thirdcontact.com> wrote in
<46115FDB.1090906 at thirdcontact.com>:
> What I wondered is if you mean it can do all of the above at once or
> any one of the above at once.  I.e. does it handle three HD
> recording stream while doing 2 HD playback streams and doing four
> (transcoding|realtime commflagging) jobs?

I've already replied to this message with a "yes," but here is more
detail. Right now, my setup is recording three streams (two FireWire
HD, one OTA non-HD [but which bitrate and resulting file size is
essentially HD-like]) while playing a fourth HD stream and running
three commflag jobs (two realtime) on "High."

My MythTV setup has two main parts, each running 0.20-fixes (ATrpms)
plus various patches (especially from SVN tickets 1457 [128-24-512],
1660, and 1744), both mine and from svn, on Fedora Core 6:
* frontend/master backend - 3.0GHz Pentium 4 with Hyper-Threading, 2GB
  RAM + using 500MB swap, 1.5TB JFS RAID 5 array, Nvidia 6200, 1080p
  and Bob deinterlacing, no XvMC.
* slave backend - 1.6GHz Quad-core "Clovertown" Xeon, 2GB RAM + using
  no swap, JFS RAID 6 array.
* Gigabit router, CIFS network file system.

As the the slave backend's ginormous RAID 6 array is sadly almost
full, all recordings, playback, and commflagging currently involve the
RAID 5 array on the frontend/master backend. The RAID 5 array also
holds the MySQL database and associated logfiles. All tuners are
located at the frontend/master backend. The slave backend runs all the
commflag jobs. The slave backend also runs a single VMware virtual
machine niced to -17, and two Apache sessions (one for MythWeb and one
for VMware monitoring).

My observations:
* First, and most-importantly: The playback is rock solid. I see no
  skips whatsoever.
* Jumps to different places in the playback occur in under one
  second. This is not appreciably different performance from that in
  less-stressful times.
* The frontend/backend's load is about 2.75. Top processes:
  mythfrontend (40-50%), Xorg/mythbackend/smbd (each about
  10%). Interestingly, Watch Recordings' live preview (I use the non
  CPU-light version) sends mythfrontend's CPU usage to 75-120% and the
  load up to 3.75.
* The slave backend's load is about 3.5-4.5. Top processes:
  mythcommflag/mythcommflag/mythcommflag (each about 40-100%),
  vmware-vmx (10%).
* Based on final elapsed times, the OTA recording finished 7 seconds
  short and one of the two FireWire recordings finished 12 seconds
  short, both within normal levels given typical startup times. (The
  other FireWire recording's elapsed time is inaccurate due to
  <URL:http://svn.mythtv.org/trac/ticket/799>, but the resulting false
  figure is well within the previously-observed range.)

-- 
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US


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