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    SubjectRe: dynamically changing available memory
    Date
    > 
    > David Ford wrote:
    > > it would please me to no end to be able to pull out a failing/failed
    > > memory module and replace it and the kernel continue on it's merry little
    > > way.
    > sure and the simm-dimmdaemon with the knowledge of yer chipset,
    > will tell ye which rammodule of Bank(0..x) to replace,
    > 'cause of sig11 and similar HW/Mem_Errors.
    >
    > Har, har

    well, one day, yes...
    it doesn't take much, really

    as a solution to the how-can-i-use-discontiguous-memory thread, too,
    one day we should have in-memory images implicitly resident on the 'swapfile'
    /dev/mem (with a swap_priority of 0, as distinct from the current -1, -2, ...)
    then we could implement the above proposal with swapoff-like semantics,
    removing an address range.

    what happens to the procs/kernel_structures/etc living there?
    same as what happens when a swap-space develops errors!
    if you'rre paranoid enuff, you use mem as a RAID device.
    not easy, to implement, but that's the generalisation you base it on.

    but the easy part which comes with this generalisation is that one can
    *add* memory --- the gap-at-16Mb and mem-bigger-than-64Mb problems
    go away when you can just boot a vanilla kernel using at most 15Mb,
    and then do a "swapon -priority=0 -lo=15Mb -hi=192Mb /dev/mem"
    from the usual /etc/rc*.

    anything with swap-prio >= 0 is real mem!

    i can imagine handling that scarce resource of L2 cache as prio==1
    and L1 cache as prio==2, and the goodness() function deriving its
    current-proc-is-favoured policy from posession of a prio==3 resource
    representing running-on-this-processor.
    the using-fpu property is similar.

    play with it.
    i suspect linus et al already have this in mind,
    that's what the -ve swap priorities immediately suggested to me....


    Peter Swain ^..^ +61 2 9698 2322 (office)
    swine@softway.com.au (00) +61 419 431 088 (mobile)
    Evolutionary software, revolutionary results +61 2 9519 0171 (home)

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