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    DateMon, 23 Sep 2002 09:16:33 +0200
    FromJens Axboe <>
    SubjectRe: 2.5.38-mm2
    On Sun, Sep 22 2002, Andrew Morton wrote:
    > +read-latency.patch
    > 
    >  Fix the writer-starves-reader elevator problem.  This is basically
    >  the read_latency2 patch from -ac kernels.
    > 
    >  On IDE it provides a 100x improvement in read throughput when there
    >  is heavy writeback happening.  40x on SCSI.  You need to disable
    
    Ah interesting. I do still think that it is worth to investigate _why_
    both elevator_linus and deadline does not prevent the read starvation.
    The read-latency is a hack, not a solution imo.
    
    >  tagged command queueing on scsi - it appears to be quite stupidly
    >  implemented.
    
    Ahem I think you are being excessively harsh, or maybe passing judgement
    on something you haven't even looked at. Did you consider that you
    _drive_ may be the broken component? Excessive turn-around times for
    request when using deep tcq is not unusual, by far.
    
    -- 
    Jens Axboe
    
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