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CONFIG_SCSI_NCR53C8XX_DEFAULT_TAGS: default tagged command queue depth

General informations

The Linux kernel configuration item CONFIG_SCSI_NCR53C8XX_DEFAULT_TAGS has multiple definitions:

default tagged command queue depth found in drivers/scsi/Kconfig

The configuration item CONFIG_SCSI_NCR53C8XX_DEFAULT_TAGS:

Help text

"Tagged command queuing" is a feature of SCSI-2 which improves performance: the host adapter can send several SCSI commands to a device's queue even if previous commands haven't finished yet. Because the device is intelligent, it can optimize its operations (like head positioning) based on its own request queue. Some SCSI devices don't implement this properly; if you want to disable this feature, enter 0 or 1 here (it doesn't matter which).

The default value is 8 and should be supported by most hard disks. This value can be overridden from the boot command line using the 'tags' option as follows (example): 'ncr53c8xx=tags:4/t2t3q16/t0u2q10' will set default queue depth to 4, set queue depth to 16 for target 2 and target 3 on controller 0 and set queue depth to 10 for target 0 / lun 2 on controller 1.

The normal answer therefore is to go with the default 8 and to use a boot command line option for devices that need to use a different command queue depth.

There is no safe option other than using good SCSI devices.

default tagged command queue depth found in drivers/scsi/Kconfig

The configuration item CONFIG_SCSI_NCR53C8XX_DEFAULT_TAGS:

Help text

"Tagged command queuing" is a feature of SCSI-2 which improves performance: the host adapter can send several SCSI commands to a device's queue even if previous commands haven't finished yet. Because the device is intelligent, it can optimize its operations (like head positioning) based on its own request queue. Some SCSI devices don't implement this properly; if you want to disable this feature, enter 0 or 1 here (it doesn't matter which).

The default value is 8 and should be supported by most hard disks. This value can be overridden from the boot command line using the 'tags' option as follows (example): 'ncr53c8xx=tags:4/t2t3q16/t0u2q10' will set default queue depth to 4, set queue depth to 16 for target 2 and target 3 on controller 0 and set queue depth to 10 for target 0 / lun 2 on controller 1.

The normal answer therefore is to go with the default 8 and to use a boot command line option for devices that need to use a different command queue depth.

There is no safe option other than using good SCSI devices.

Hardware

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