lkml.org 
[lkml]   [2004]   [Nov]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: Suspend 2 merge: 43/51: Utility functions.
    From
    Date
    Hi.

    On Sun, 2004-11-28 at 03:11, Dave Hansen wrote:
    > On Thu, 2004-11-25 at 16:04, Nigel Cunningham wrote:
    > > On Fri, 2004-11-26 at 10:46, Pavel Machek wrote:
    > > > How many bits do you need? Two? I'd rather use thow two bits than have
    > > > yet another abstraction. Also note that it is doing big order
    > > > allocation.
    > >
    > > Three if checksumming is enabled IIRC. I'll happily use normal page
    > > flags, but we only need them when suspending, and I understood they were
    > > rarer than hen's teeth :>
    > >
    > > MM guys copied so they can tell me I'm wrong :>
    >
    > Please remember that, in almost all cases, any use of page->flags can be
    > replaced by a simple list. Is a page marked foo? Well, just traverse
    > this data structure and see if the page is in there. It might be a
    > stinking slow check, but it will *work*.
    >
    > I think we're up to using 1 bit in the memory hotplug code, but we don't
    > even need that if some operations can be implemented more slowly.

    Yes. That's the way suspending did things initially like checking which
    pages were free. The bitmap was added to turn O(n^2) into O(n). Since
    the calculations can potentially be done a few times (as memory is freed
    so we can suspend), it was a big gain to use a bitmap.

    Regards,

    Nigel
    --
    Nigel Cunningham
    Pastoral Worker
    Christian Reformed Church of Tuggeranong
    PO Box 1004, Tuggeranong, ACT 2901

    You see, at just the right time, when we were still powerless, Christ
    died for the ungodly. -- Romans 5:6

    -
    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 14:08    [W:4.120 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site