Re: [RFC] AHCI Command Completion Coalescing(CCC) proposal

[Jeff Garzik <jgarzik@pobox.com>]

zhao, forrest wrote:
> Hello, all
> 
> 0 Why this RFC?
> Although AHCI spec 1.1 provides a detailed explanation about how to play
> with CCC-related registers to enable CCC, several CCC-policy-related
> parameters need to be defined(or the consensus need to be achieved)
> before we start to write the code.

To brag a bit, I pushed Intel heavily for this feature, in the 
pre-AHCI-1.0 development days.


>>From my understanding, the measurement of "IRQ numbers per second"
> should be based on per-port instead of all ports of a SATA controller.

No, it should be all ports of a SATA controller.

If an interrupt arrives while CCC is active, we should take the 
opportunity to check all ports for activity -- as the standard code does 
now.


> 4 What should the software specified timeout be?
> I don't have the strong reasoning of a specific timeout value. 500ms? or
> 1000ms? We should trade-off between the delay and overhead.

500ms is a lot of latency.

	Jeff