Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 12 May 2003 15:42:43 -0400 | From | Jeff Garzik <> | Subject | Re: 2.5.69, IDE TCQ can't be enabled |
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On Mon, May 12, 2003 at 11:58:10AM -0600, Mudama, Eric wrote: > The only difference between SATA TCQ and PATA TCQ is that in PATA TCQ, the > drive doesn't report the active tag bitmap back to the host after each > command. Other than that they are functionally identical to my > understanding. (Yes, there are options like first-party DMA, but these are > not requirements)
That's from the "drive side." From the OS side, the ideal implementation isn't here yet :)
Ideally there is a DMA ring of taskfiles and scatterlists. The OS (producer) queues these up asynchrously, and the host+devices (consumer) executes the taskfiles in the ring. AHCI does this.
With PATA TCQ, we only have a single scatterlist, and are forced to have more OS-side infrastructure for command queueing, processing, etc.
As an aside, as drives and hosts get faster, we will actually want _fewer_ interrupts (i.e. interrupt coalescing).
All this points to making the host smarter. The drives are already pretty damn smart ;-)
Jeff
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