[lkml]   [2007]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [00/17] Large Blocksize Support V3
    Mel Gorman wrote:
    > On (26/04/07 16:50), Nick Piggin didst pronounce:

    >>Fragmentation is the problem. The anti-frag patches don't actually
    >>guarantee anything about fragmentation, and even if they did, then
    > The grouping pages by mobility do not guarantee anything but the memory
    > partition (kernelcore= boot parameter) does give hard guarantees about
    > the amount of memory that is "movable". Of course, the partition requires
    > configuration at boot-time so it's less than ideal but it does give hard
    > guarantees.

    For the hugepages people, I can understand that's a solution. But that's
    the last thing you want to do on a system with a limited amount of memory,
    or a regular Joe's desktop/server.

    > Indeed but then you have to deal with internal fragmentation
    > for pages-larger-than-TLB-page. I'm not saying it's wrong but it does
    > come with it's own set of issues.

    None of them is perfect (the ways to increase the size of pagecache pages,
    that is).

    I think in the long term, TLB page sizes will probably increase a little
    bit... but if a given page size is "good enough" for a CPU, they really
    should be good enough for other hardware. I mean, come on, the CPU's TLB
    has to have a good hit ratio and handle several lookups per cycle with a
    3-cycle latency on 3GHz+ hardware... surely a an IO controller's
    scatter-gather engine or IOMMU that has to do a few lookups per disk IO
    is nowhere near so critical as a CPU's datapath: just add a few more
    entries to it, they've already got hundreds of megs of cache, so that
    isn't an issue either.

    SUSE Labs, Novell Inc.
    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: 2007-04-26 10:57    [W:0.020 / U:2.640 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site