[lkml]   [2007]   [Mar]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear)
    On Wednesday 07 March 2007 10:44, Bill Irwin wrote:
    > On Wed, Mar 07, 2007 at 10:28:21AM +0100, Nick Piggin wrote:
    > > Depending on whether anyone wants it, and what features they want, we
    > > could emulate the old syscall, and make a new restricted one which is
    > > much less intrusive.
    > > For example, if we can operate only on MAP_ANONYMOUS memory and specify
    > > that nonlinear mappings effectively mlock the pages, then we can get
    > > rid of all the objrmap and unmap_mapping_range handling, forget about
    > > the writeout and msync problems...
    > Anonymous-only would make it a doorstop for Oracle, since its entire
    > motive for using it is to window into objects larger than user virtual
    > address spaces (this likely also applies to UML, though they should
    > really chime in to confirm).

    We need it for shared file mappings (for tmpfs only).

    Our scenario is:
    RAM is implemented through a shared mapped file, kept on tmpfs (except by dumb
    users); various processes share an fd for this file (it's opened and
    immediately deleted).

    We maintain page tables in x86 style, and TLB flush is implemented through

    Having a VMA per each 4K is not the intended VMA usage: for instance, the
    default /proc/sys/vm/max_map_count (64K) is saturated by a UML process with
    64K * 4K = 256M of resident memory.

    > Restrictions to tmpfs and/or ramfs would
    > likely be liveable, though I suspect some things might want to do it to
    > shm segments (I'll ask about that one).

    > There's definitely no need for a
    > persistent backing store for the object to be remapped in Oracle's case,
    > in any event. It's largely the in-core destination and source of IO, not
    > something saved on-disk itself.
    > -- wli

    Inform me of my mistakes, so I can add them to my list!
    Paolo Giarrusso, aka Blaisorblade
    Chiacchiera con i tuoi amici in tempo reale!*

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-03-08 13:43    [W:0.021 / U:150.444 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site