I am writing a real time program to read data from a custom hardware and write the data and simultaneously provide display by reading the data from disk.
My read and write process are synchronised and are running with SCHED_FIFO scheduling with highest priority of 99 and 98 and my display is runnning with priority 95 under SCHED_FIFO scheduling only.

So now the display process is not in any critical section. My read should cater to the device with in 23.2 millisecs and it is not Interrupt driven but SCSI device.

Some time i see it does not cater to the read even though it is the highest priority proc. WHY?

2) Observation what i have seen is i am using 1GB memory and my system is having 2.0 GB Main memory.,but when some processes get scheduled before my process,they increase the cache in the system ,so when i get scheduled ,the processor puts others into swap and some times does paging when my real time process is running,which is very serious when real time programming is going on ,how to clear the cache and avoid the processor doing any paging when my process is running.