Re: [PATCH] speed up SATA

Andrew Morton
2004-03-28T01:03:04Z

Jeff Garzik <jgarzik@pobox.com> 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.