lkml.org 
[lkml]   [1998]   [Dec]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: mmap() is slower than read() on SCSI/IDE on 2.0 and 2.1
    On Fri, Dec 18, 1998 at 09:05:26PM +0100, Rik van Riel wrote:

    > Some form of read-behind will give us optimal performance
    > when the tiles are a lot smaller (say 1/4th) than the VM
    > 'stripe size' we are using.

    Still wearning my "I'm not sure its always a good idea to second
    guess the application hat" -- do we actually have any applications
    that would make use of this?

    The only one I can think of is that I have large databases (well, 1
    GB or so) that have sequentially grown and at time, we do queries
    that requires us walking backwards though the data here, but I don't
    think it uses mmap.

    I know other `theorietical applications' exist that produce this
    pattern, but then I can find `theorietical applications' that have
    any kind of screwy access pattern.

    > The actual disk I/O, of course, is still done in forward
    > direction :)

    True... but if this is an issue, gobs of disk and RAID can help,
    especially when it comes to random seeks.



    -cw

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

    \
     
     \ /
      Last update: 2005-03-22 13:46    [W:4.157 / U:0.180 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site