lkml.org 
[lkml]   [2002]   [Aug]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: large page patch (fwd) (fwd)


    On Sat, 3 Aug 2002, David Mosberger wrote:
    >
    > Your point about wanting databases have access to giant pages even
    > under memory pressure is a good one. I had not considered that
    > before. However, what we really are talking about then is a security
    > or resource policy as to who gets to allocate from a reserved and
    > pinned pool of giant physical pages.

    Absolutely. We can't allow just anybody to allocate giant pages, since
    they are a scarce resource (set up at boot time in both Ingo's and Intels
    patches - with the potential to move things around later with additional
    interfaces).

    > You don't need separate system
    > calls for that: with a transparent superpage framework and a
    > privileged & reserved giant-page pool, it's trivial to set up things
    > such that your favorite data base will always be able to get the giant
    > pages (and hence the giant TLB mappings) it wants. The only thing you
    > lose in the transparent case is control over _which_ pages need to use
    > the pinned giant pages. I can certainly imagine cases where this
    > would be an issue, but I kind of doubt it would be an issue for
    > databases.

    That's _probably_ true. There aren't that many allocations that ask for
    megabytes of consecutive memory that wouldn't want to do it. However,
    there might certainly be non-critical maintenance programs (with the same
    privileges as the database program proper) that _do_ do large allocations,
    and that we don't want to give large pages to.

    Guessing is always bad, especially since the application certainly does
    know what it wants.

    Linus

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:27    [W:0.022 / U:92.308 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site