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    SubjectRe: [PATCH] cfq-iosched: NCQ SSDs do not need read queue merging
    On 01/10/2010 04:04 PM, Corrado Zoccolo wrote:
    > NCQ SSDs' performances are not affected by
    > distance of read requests, so there is no point in having
    > overhead to merge such queues.
    >
    > Non-NCQ SSDs showed regression in some special cases, so
    > they are ruled out by this patch.
    >
    > This patch intentionally doesn't affect writes, so
    > it changes the queued[] field, to be indexed by
    > READ/WRITE instead of SYNC/ASYNC, and only compute proximity
    > for queues with WRITE requests.
    >
    > Signed-off-by: Corrado Zoccolo<czoccolo@gmail.com>

    That's not really true. Overhead always increases as the total number
    of ATA commands issued increases.

    Jeff






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