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    SubjectRe: Problem with 1G RAM
    On Fri, 4 Dec 1998, Neil Conway wrote:

    > OK, who wants to volunteer to insert a check in the kernel: STOP if
    > __PAGE_OFFSET is incompatible with the amount of RAM specified by
    > "mem=xxxM" ? Failing that, print a warning, and reduce the RAM to
    > (say) 960MB or whatever.

    mirkwood:~/linux/arch/i386/kernel# grep MAXMEM *
    setup.c:#define MAXMEM ((unsigned long)(-PAGE_OFFSET-VMALLOC_RESERVE))
    setup.c: if (memory_end > MAXMEM)
    setup.c: memory_end = MAXMEM;
    mirkwood:~/linux/arch/i386/kernel#

    It looks to me that there already is code like this inside
    kernel 2.1.131. Question is why it doesn't work correctly.

    Let's see what happens:

    MAXMEM = -0xC0000000-(64<<20)

    The only reason this could go wrong is when something fouls
    up with the conversion from a signed to an unsigned number.

    In that case:

    #define MAXMEM (MAX_INT - PAGE_OFFSET - VMALLOC_RESERVE + 1)

    then again, I may have overlooked something silly :)

    cheers,

    Rik -- the flu hits, the flu hits, the flu hits -- MORE
    +-------------------------------------------------------------------+
    | Linux memory management tour guide. H.H.vanRiel@phys.uu.nl |
    | Scouting Vries cubscout leader. http://www.phys.uu.nl/~riel/ |
    +-------------------------------------------------------------------+


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