Re: [PATCH] speed up SATA

[Jeff Garzik]

Jamie Lokier wrote:
> Jeff Garzik 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.
>
>
> Does TCQ-on-write allow you to do ordered write commits, as with barriers,
> but without needing full cache flushes, and still get good performance?

Nope, TCQ is just a bunch of commands rather than one.  There are no 
special barrier indicators you can pass down with a command.

	Jeff




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