Maximum number of TCQ commands per device


Linux Kernel Configuration
└─>Device Drivers
└─>SCSI device support
└─>SCSI low-level drivers
└─>Maximum number of TCQ commands per device
In linux kernel since version 2.6.12  
Specify the number of commands you would like to allocate per SCSI
device when Tagged Command Queueing (TCQ) is enabled on that device.

This is an upper bound value for the number of tagged transactions
to be used for any device. The aic7xxx driver will automatically
vary this number based on device behavior. For devices with a
fixed maximum, the driver will eventually lock to this maximum
and display a console message indicating this value.

Due to resource allocation issues in the Linux SCSI mid-layer, using
a high number of commands per device may result in memory allocation
failures when many devices are attached to the system. For this reason,
the default is set to 32. Higher values may result in higher performance
on some devices. The upper bound is 253. 0 disables tagged queueing.

Per device tag depth can be controlled via the kernel command line
"tag_info" option. See Documentation/scsi/aic79xx.rst for details.