SuSE Linux: Versions up to (including) 7.0
This article refers to an older version of SuSE Linux.
Therefore some of the informations given in this article may
be outdated or the article may contain stale links.
CONFIG_AIC7XXX_TCQ_ON_BY_DEFAULT This option causes the aic7xxx driver to attempt to use tagged command queueing on any devices that claim to support it. If this is set to yes, you can still turn off TCQ on troublesome devices with the use of the tag_info boot parameter. See /usr/src/linux/drivers/scsi/README.aic7xxx for more information on that and other aic7xxx setup commands. If this option is turned off, you may still enable TCQ on known good devices by use of the tag_info boot parameter. If you are unsure about your devices then it is safest to say N here. However, TCQ can increase performance on some hard drives by as much as 50% or more, so I would recommend that if you say N here, that you at least read the README.aic7xxx file so you will know how to enable this option manually should your drives prove to be safe in regards to TCQ. Conversely, certain drives are known to lock up or cause bus resets when TCQ is enabled on them. If you have a Western Digital Enterprise SCSI drive for instance, then don't even bother to enable TCQ on it as the drive will become unreliable, and it will actually reduce performance.It seems like having this option not turned on by default severely impacts the hard disk performance on IBM hard disk drives - we did not experience such bad values on other systems so far. For this reason and since it still can be disabled with a boot parameter, we have now enabled this feature by default for all future SuSE kernel packages (from 7.1 on).
zgrep TCQ /proc/config.gzOn older versions, please check the kernel configuration file.
# CONFIG_AIC7XXX_TCQ_ON_BY_DEFAULT is not setSuSE Linux 7.1 and other systems with this feature enabled will show:
CONFIG_AIC7XXX_TCQ_ON_BY_DEFAULT=yFortunately, it is not necessary to recompile the kernel to enable this feature. You can pass a boot parameter to enable TCQ on specific drives.
"aic7xxx=tag_info:{{8,8..},{8,8..},..}" This option is used to disable or enable Tagged Command Queueing (TCQ) on specific devices. As of driver version 5.1.11, TCQ is now either on or off by default according to the setting you choose during the make config process. In order to en/disable TCQ for certian devices at boot time, a user may use this boot param. The driver will then parse this message out and en/disable the specific device entries that are present based upon the value given. The param line is parsed in the following manner: { - first instance indicates the start of this parameter values second instance is the start of entries for a particular device entry } - end the entries for a particular host adapter, or end the entire set of parameter entries , - move to next entry. Inside of a set of device entries, this moves us to the next device on the list. Outside of device entries, this moves us to the next host adapter . - Same effect as , but is safe to use with insmod. x - the number to enter into the array at this position. 0 = Enable tagged queueing on this device and use the default queue depth 1-254 = Enable tagged queueing on this device and use this number as the queue depth 255 = Disable tagged queueing on this device. Note: anything above 32 for an actual queue depth is wasteful and not recommended. A few examples of how this can be used: tag_info:{{8,12,,0,,255,4}} This line will only effect the first aic7xxx card registered. It will set scsi id 0 to a queue depth of 8, id 1 to 12, leave id 2 at the default, set id 3 to tagged queueing enabled and use the default queue depth, id 4 default, id 5 disabled, and id 6 to 4. Any not specified entries stay at the default value, repeated commas with no value specified will simply increment to the next id without changing anything for the missing values. tag_info:{,,,{,,,255}} First, second, and third adapters at default values. Fourth adapter, id 3 is disabled. Notice that leading commas simply increment what the first number effects, and there are no need for trailing commas. When you close out an adapter, or the entire entry, anything not explicitly set stays at the default value. A final note on this option. The scanner I used for this isn't perfect or highly robust. If you mess the line up, the worst that should happen is that the line will get ignored. If you don't close out the entire entry with the final bracket, then any other aic7xxx options after this will get ignored. So, in general, be sure of what you are entering, and after you have it right, just add it to the lilo.conf file so there won't be any mistakes. As a means of checking this parser, the entire tag_info array for each card is now printed out in the /proc/scsi/aic7xxx/x file. You can use that to verify that your options were parsed correctly.Enabling TCQ via the boot parameter dramatically increased the performance on the tested systems.
liloHint: Our customer Herr Griem told us, that you may run into difficulties when using an initial ramdisk caused by the delimeter comma (,). In /usr/src/linux/drivers/scsi/README.aic7xxx is stated:
Module Loading command options ------------------------------ When loading the aic7xxx driver as a module, the exact same options are available to the user. However, the syntax to specify the options changes slightly. For insmod, you need to wrap the aic7xxx= argument in quotes and replace all ',' with '.'. So, for example, a valid insmod line would be: insmod aic7xxx aic7xxx='verbose.irq_trigger:1.extended'Please replace all commas with periods.