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    SubjectRe: [PATCH][RFC] simpler __alloc_pages{_limit}
    On Saturday den 25 August 2001 13:55, Stephan von Krawczynski wrote:
    > On Sat, 25 Aug 2001 02:48:28 +0200
    > Roger Larsson <> wrote:
    > > Hi again,
    > >
    > > [two typos corrected from the version at linux-mm]
    > > [...]
    > > Doing this - the code started to collaps...
    > > __alloc_pages_limit could suddenly handle all special cases!
    > > (with small functional differences)
    > >
    > > Comments?
    > Hi Roger,
    > I tested your page against straight 2.4.9 (where it applied mostly, the
    > rest I did manually) and experience the following:
    > 1) system gets slow, even in times where plenty of free memory is
    > available. There must be some overhead inside.

    It is not unlikely because it care too much about the higher order
    allocations. It needs a higher order page and really tries...

    > 2) It does not really work around the basic problem of too
    > many cached pages in case of heavy filesystem action, I do get the already
    > known "kernel: __alloc_pages: 2-order allocation failed." by simply copying
    > files a lot.

    Is this with raiserfs and/or nfs? And without highmem support?
    Why is 2-order allocations needed???
    Can anyone answer?
    Higher order allocs during normal operation is not that nice...

    > 3) Even in high load situations the CPU load seems to get
    > worse, I made it up to 7 with normal file copying on a SMP 1GHz 1GB RAM
    > machine.

    Might also be related to the higher order. Freeing too much inactive pages
    to satisfy the request...
    SMP might be a factor since the patch will go harder on the locks...

    > Hm, I guess that doesn't really work as you expected.

    Well, I make a version that gives up on higher order allocations more

    But the real problem might be - why are the higher order allocations
    needed anyway?


    Roger Larsson
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