1. If I have 1 gig physical memory and CONFIG_HIGHMEM disabled, would
the user processes be able to see the high memory?
Only 256 meg (this is on BCM1250; so 256 meg is expected) shows up in
/proc/meminfo and I couldn't malloc more than that much from user processes.
2. With highmem enabled, is there a penalty to the user processes? From
what I understood, highmem mappings are needed for the kernel to access
that memory. For the pages belonging to user processes, does it still
3. How do I measure the penalty of highmem on kernel modules? Since the
code and data for modules resides in highmem, the kernel has to
constantly map and unmap while running inside the modules? Is there a
way to quantify the overhead of running with highmem enabled versus not?
thanks in advance!