Michael Tokarev wrote:
/sys/block/sdX/device/queue_depth file is read-write with
libsata, but is read-only with SCSI controllers (at least
with the ones we have -- mostly aic7xxx or mptsas).
Googling for "disable tcq" gives results about {dis,en}abling
TCQ at boot time, and also mentions ipr (which we don't have).
Is there an option to control TCQ at runtime?
You have found the correct sysfs file -- but read/write access to it
requires the SCSI driver to implement the ->change_queue_depth() hook.
'grep -w' will show that not too many drivers have implemented this yet,
mostly the newer ones. For older drivers, poke around and see if there
is a driver-specific module option or somesuch.
Jeff
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