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?
Best, -at