[CentOS] pdflush kernel thread pops up every 10 seconds or so and video decoding grinds to a halt for 1/2 a second

Tue Oct 19 01:25:41 UTC 2010
Aleksey Tsalolikhin <atsaloli.tech at gmail.com>

Hi. A friend of mine was doing real-time video decoding on
Fedora Core 13 and he had a performance glitch (1/2 a second
freeze) every 5-10 seconds.  "top" showed flush-253:0
process at the moment of the freeze.

Major device number 253 corresponds to device-mapper.  I advised my
friend to re-install his FC13 without LVM, to see if the glitch
is related to LVM.

After re-installing FC13 without LVM, he is seeing the glitch
every 10 seconds, and it shows flush-8:16 where before it said
flush-253:0.  8 is scsi disk driver. So it's not an LVM thing...
maybe a kernel thing?

I suggested he try Fedora 14 beta, as it has a newer kernel.
Maybe this kernel thing is fixed in the newer kernel.

He also tried CentOS 5.5, and saw a "pdflush" process popping
up with the same frequency, and resulting in a similar glitch.

Any other suggestions?