[mythtv-users] mythbackend CPU spikes in "watch recordings"?

Niklas Brunlid prefect47 at gmail.com
Mon Dec 28 12:24:04 UTC 2009


First of all, a big thanks to all developers and testers. I've used mythtv
since around 2003 and my VCR has been collecting dust ever since. My
harddrive expenses have gone up a bit though... =)

I run Fedora 11 on an Asus K8V with an AMD64 3000+ and an nVidia nnnn, using
DVI->HDMI to a FullHD LCD TV and the SP/DIF of the mainboard directly to the
amplifier. The system is somewhat regularly updated against the Fedora and
ATrpms repos. MythTV version is release-0-22-fixes 22973. Everything runs on
the same computer.

My problem is that the UI is extremely slow, like when I step around in the
"watch recordings" screen. It seems that mythbackend responds VERY slowly -
if I queue up 10-20 key presses up or down and switch to a console window,
"top" tells me that mythbackend is using a lot of CPU (at least 80-90%) when
these keypresses are handles by the frontend. It's only mythbackend and not
the mythfrontend or mysql processes though. It feels like each step up or
down takes seconds.
The effect is the same in the Terra, MythBuntu and blue-abstract themes.

I've read that constant regeneration of snapshot images could slow down the
system, but this happens in both panes of "watch recordings" and in the left
one no snapshots are shown. All my recording and mythvideo drives are
noatime/nodiratime but not my system drive:

/etc/fstab extract:
LABEL=myth1tb-disk1  /myth/bigdisk1 ext3  noatime,nodiratime,data=writeback
1 2
LABEL=myth1tb-disk2  /myth/bigdisk2 ext3  noatime,nodiratime,data=writeback
1 2
LABEL=myth1tb-disk3  /myth/bigdisk3 ext3  noatime,nodiratime,data=writeback
1 2
LABEL=myth1tb-disk4  /myth/bigdisk4 ext3  noatime,nodiratime,data=writeback
1 2

/ Niklas
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