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    SubjectRe: Raid 0 Swap?
    Date
    On Monday 04 September 2006 12:46, Jan Engelhardt wrote:
    > >> I thought kernel data weren't swapped at all?
    >
    > If the swap code was swapped, who would swap it in again?
    >
    > >Well, it's not that simple. Kernel uses both swappable and
    > >non-swappable memory internally. For some things, it's
    > >unswappable, for some, it's swappable. In general, it's
    > >impossible to say which parts of kernel will break (and
    > >in wich ways) if swap goes havoc.
    >
    > In general, everything you type in as C code (.bss, .data, .text) should be
    > unswappable. kmalloc()ed areas are resident too, and kmalloc has a
    > parameter which defines whether the allocation can/cannot push userspace
    > pages into the swap (GFP_ATOMIC/GFP_IO). So if there is some
    > kernel-allocation swapped out, it is most likely to be marked as
    > 'userspace' so that the same algorithms can be used for swapin and -out.

    What are you guys talking about? IIRC kernel doesn't use
    swap for its vital data structures. I recall only one
    kernel thing which goes into swap: tmpfs data. Caching network
    filesystems may also use swappable data, but currently grep
    catches only cifs.

    IOW swap is for dirtied userspace data. Please correct me
    if I am wrong here.
    --
    vda
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