Mark Lord wrote:
Gwendal Grignou wrote:
Jeff, you're right, I made some mistakes:
- Reading SiI3132 doc again, it only supports 32 command per port, so
the tags must be share among all the drives behind the same port.
But other chipset does support up to 128 commands per port.
- Jens' patch is working when all disks support NCQ. Only when we have
a mix of drives with or without NCQ we have a problem.
..
Along those lines, the newer Marvell chipsets support up to 128 commands
per host port.
I seem to recall that the Pacific Digital Qstor chip
can manage an insane number of commands -- something like
32 per device per PM port [eg. (15 * 32) in total per host port].
Seems to be a widespread kind of thing for non-legacy chipsets.
Someday we really ought to beef up libata to allow host-chipset queuing
of non-NCQ commands, too.
SAS+SATA chips do not necessarily have per-port limits at all, even.
The limit may instead be a host-wide command queue size limit, rather
than a per-port limit.
Jeff
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