[lkml]   [2002]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
    On 5 January 2002 10:59, M. Edward (Ed) Borasky wrote:

    > OK, here's some pseduo-code for a real-world test case. I haven't had a
    > chance to code it up, but I'm guessing I know what it's going to do. I'd
    > *love* to be proved wrong :).
    > # build and boot a kernel with "Magic SysRq" turned on
    > # echo 1 > /proc/sys/kernel/sysrq
    > # fire up "nice --19 top" as "root"
    > # read "MemTotal" from /proc/meminfo
    > # now start the next two jobs concurrently
    > # write a disk file with "MemTotal" data or more in it

    Like dd if=/dev/zero of=/tmp/file bs=... count=... ?

    > # perform a 2D in-place FFT of total size at least "MemTotal/2" but less
    > # than "MemTotal"

    I'm willing to try. What program can I use for FFT?

    > What's worse is if the page cache gets so big that the FFT has to start
    > swapping. For those who aren't familiar with 2D FFTs, they take two
    > passes over the data. The first pass will be unit strides -- sequential
    > addresses. But the second pass will be large strides -- a power of two.
    > That second pass is going to be brutal if every page it hits has to be
    > swapped in!

    Can you describe FFT memory access pattern in more detail?
    I'd like to write a simple testcase with similar 'bad' pattern.
    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: 2005-03-22 13:15    [W:0.022 / U:6.168 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site