## page was renamed from Kernel/Reference/fwts/maxreadreq
== Firmware Test Suite - maxreadreq test ==

The Max``Read``Request feature is used to ensure a fairer bandwidth allocation of PCI Express. It specifies the largest read request any PCI Express device can generate. To reduce the way the bus is hogged by large reads one reduces the Max``Read``Request size.  Normally a BIOS will configure a system with suitable Max``Read``Request sizes for PCI Express devices and is set to ensure fairness rather than maximum performance.

This test checks to see if the Max``Read``Request size is configured too low. A value of less than 256 is considered too low as it impacts on throughput even though it reduces bus contention. Allowed values are 128, 256, 512, 1024, 2048 and 4096 bytes.

=== Examples: ===

{{{
sudo fwts maxreadreq - 
}}}

..runs the test on your machine and dumps the output to stdout. This test requires user interaction.

== Explanation of test results ==

Certain test results may require a little more explanation. This section will try and give some context to specific test failures.

||Error ID||Explanation||
||Low``Max``Read``Req||The Max``Read``Request size is set too low and will affect performance. It will provide excellent bus sharing at the cost of bus data transfer rates.  Although not a critical issue, it may be worth considering setting the Max``Read``Request size to 256 or 512 to increase throughput on the PCI Express bus. Some drivers (for example the Brocade Fibre Channel driver) allow one to override the firmware settings. Perhaps this is a BIOS configuration setting that can be modified, if so, it may be worth increasing it.||