Re: [PATCH] speed up SATA

[Jeff Garzik]

Andrew Morton wrote:
> 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.

If the disk is smart there are surely opportunities for latency 
optimization as well...


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

rotfl ;-)  True that...

"IOPs" are what make a lot of storage peeps excited these days, so they 
are being pushed in a low-latency direction anyway.

	Jeff



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