I have 4 systems, dual P4 2.2GHz w/2G memory each. We have a VMIC Reflective Memory Card in each system, which acts like global shared memory to each system using a fiber ring for communication.
Using RH 7.1, I had to set a few things in the 'xconfig' to get the cards to work. "CONFIG_HIGHMEM4G=y" and I had to reduce the virtual memory from the automatic 3G down to 1G to get these cards mapped into the system.
Now with RH 8, there is no longer a setting to adjust the virtual memory, and since I have 2G physical memory, the memory mapping fills up to the max of 4G before my cards are ever seen.
If I add "mem=800MB" to the boot-up options the system will see the VMIC cards and they work fine. Otherwise the driver for the cards will not open the device because it cannot map/find the memory.
I have two other questions about this issue posted, 60 people have read them, no one has responded? I need to talk to someone that is savvy with the memory scheme of RH/Linux.....