Re: [PATCH] speed up SATA

[Andrew Morton]

Jeff Garzik <jgarzik@xxxxxxxxx> wrote:
>
>  TCQ-on-write for ATA disks is yummy because you don't really know what 
>  the heck the ATA disk is writing at the present time.  By the time the 
>  Linux disk scheduler gets around to deciding it has a nicely merged and 
>  scheduled set of requests, it may be totally wrong for the disk's IO 
>  scheduler.  TCQ gives the disk a lot more power when the disk integrates 
>  writes into its internal IO scheduling.

Slightly beneficial for throughput, disastrous for latency.

It appears the only way we'll ever get this gross misdesign fixed is to add
a latency test to winbench.

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