Linux slow with more memory - solution & patch

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Hmm - so I probably should apologize for my previous postings. Not only that my mainboard is unable to cache > 16MB of RAM, it even prevents CPU to cache it in L1. Which is bad, bad, BAD.

I made following patch, which tries to solve the problem: You can specify amount of fastmem= on commandline, and it will try to use slow memory for buffers, and fast memory for everything else. This patch probably damages performance of __get_free_pages badly, otherwise it should be ok.

It helped to my machine: (Compilation of kernel:)
mem=20M                 32 minutes (if I recall correctly)
mem=20M fastmem=16M     24 minutes
mem=16M                 22 minutes

Note that there still is some performance loosage in there. But if something more than kernel compilation happened, performance might be better with this than with memory completely disabled.

Please, some wizard, take a look at this. (Patch is against 2.1.36)