lowmem/highmem

Hello
I searched forums ,couldnot find a thread related to this.Can you explain what is this about? or can you offer few links I can read?
Thanks

Not absolutely shure what you mean.
Highmem ist the area within system memory that the kernel cannot address directly. on 32 Bit Systems this is above 4GB bcs the kernel uses 32 bit pointers to address the memory. Memory above 4GB is used in the manner of swap space.

Are you, by chance, looking at the output of the free command? If so, these are watermarks for the lowest and highest memory usage for the system.

I m preparing for an interview and reading article about kernel debugging ,crash dump analysis tool, "lowmem issues" is mentioned in the requirements.Anyone easily can guess it is about memory but I could not find any connection for these
How can I see these values rather than using free command? why are these values important?
Thanks