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    SubjectRe: 2.4.22pre6aa1
    On Friday 18 July 2003 00:50, Andrea Arcangeli wrote:

    Hi Andrea,

    > Can you try to change include/linux/blkdev.h like this:
    > -#define MAX_QUEUE_SECTORS (4 << (20 - 9)) /* 4 mbytes when full sized */
    > +#define MAX_QUEUE_SECTORS (16 << (20 - 9)) /* 4 mbytes when full sized */
    > This will raise the queue from 4 to 16M. That is the first(/only) thing
    > that can explain a drop in performnace while doing contigous I/O.
    > However I didn't expect it to make a difference, or at least not so
    > relevant.
    > If this doesn't help at all, it might not be an elevator/blkdev thing.
    > At least on my machines the contigous I/O still at the same speed.
    well, it doesn't help at all. I/O gets more worse with that change. (8mb/s
    less). How can this happen? *wondering*

    > You also where the only one reporting a loss of performance with
    > elevator-lowlatency, it could be still the same problem that you've
    > seen at that time.
    The only one? Surely not. Also Con tested your elevator-lowlatency and we both
    saw performance degration :)

    > can you try with data=writeback (or ext2) or hdparm -W1 and see if you
    > can still see the same delta between the two kernels? (careful with -W1
    > as it invalidates journaling)
    Yes, I'll do it later this day.

    Sorry for my late reply. I've been very busy.

    ciao, Marc

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