zhao, forrest wrote:
On Thu, 2006-06-08 at 11:01 -0400, Jeff Garzik wrote:
>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.
Maybe I didn't state my ideas clearly. Let me explain it by an example.
1 Assume there are 2 active ports(P0 and P1) on a system, they all run
under non-NCQ mode
2 During a certain period, P0 is heavily loaded, which generates >1000
interrupts per second; P1 is idle, which generates no interrupt
3
3.1 If the measurement of "IRQ numbers per second" is based on all
active ports of a SATA controller, CCC is activated by CCC_PORTS being
set to 0x3, CCC_CTL.CC being set to 64(32*2). Then the problem comes:
the CCC interrupt will be raised only when the timeout expires, this is
because P1 is in idle, thus hCccComplete can never be greater than or
equal to 64, the maximum of hCccComplete is 32.
3.2 If the measurement of "IRQ numbers per second" is based on per-port,
we can know that P0 is heavily-loaded, then CCC is activated by
CCC_PORTS being set to 0x1, CCC_CTL.CC being set to 32. Then CCC can
take effect as we have expected :)
NOTE: hCccComplete is the term used in section 11 of AHCI spec1.1
I'm still not sure I follow you?
When AHCI runs out of commands to execute, it transitions from H:Idle to
Ccc:SetIS.
IMPORTANT NOTE: In order for CCC to be effective on AHCI, ahci.c and
libata (and sata_sil24) must be updated to support queuing a list of
non-NCQ commands onto the controller, and recovering from errors in the
case where a command list full of non-NCQ commands is present.
Also, you should scale up CCC_CTL.CC really based on "commands in
flight" across all ports.
Jeff
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