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    SubjectRe: What to expect with the 2.6 VM
    On Wed, Jul 02, 2003 at 03:15:51PM -0700, William Lee Irwin III wrote:
    >> What complexity? Just unmap it if you can't allocate a pte_chain and
    >> park it on the LRU.

    On Thu, Jul 03, 2003 at 12:26:41AM +0200, Andrea Arcangeli wrote:
    > the complexity in munlock to rebuild what you destroyed in mlock, that's
    > linear at best (and for anonymous mappings there's no objrmap, plus
    > objrmap isn't even linear but quadratic in its scan [hence the problem
    > with it], though in practice it would be normally faster than the linear
    > of the page scanning ;)

    Computational complexity; okay.

    It's not quadratic; at each munlock(), it's not necessary to do
    anything more than:

    for each page this mlock()'er (not _all_ mlock()'ers) maps of this thing
    grab some pagewise lock
    if pte_chain allocation succeeded
    add pte_chain
    else
    /* you'll need to put anon pages in swapcache in mlock() */
    unmap the page
    decrement lockcount
    if lockcount vanished
    park it on the LRU
    drop the pagewise lock

    Individual mappers whose mappings are not mlock()'d add pte_chains when
    faulting the things in just like before.


    -- wli
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