CONFIG_AIC79XX_CMDS_PER_DEVICE: Maximum number of TCQ commands per device

General informations

The Linux kernel configuration item CONFIG_AIC79XX_CMDS_PER_DEVICE:

• prompt: Maximum number of TCQ commands per device
• type: int
• depends on: CONFIG_SCSI_AIC79XX
• defined in drivers/scsi/aic7xxx/Kconfig.aic79xx
• found in Linux kernels: 2.5.53–2.5.75, 2.6.0–2.6.39, 3.0–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.12, 6.13-rc+HEAD

Help text

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.

Hardware

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The data is retrived from:

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• Linux Kernel Driver DataBase (LKDDb)

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