Product specifications

F–Useful Programs and Files
Summary and Descriptions of Useful Programs
F-10 IB6054601-00 H
S
ipath_mtrr
MTRR is used by the InfiniPath driver to enable write combining to the QLogic
on-chip transmit buffers. This option improves write bandwidth to the QLogic chip
by writing multiple words in a single bus transaction (typically 64 bytes). This
option applies only to x86_64 systems. It can often be set in the BIOS.
However, some BIOS’ do not have the MTRR mapping option. It may have a
different name, depending on the chipset, vendor, BIOS, or other factors. For
example, it is sometimes referred to as 32 bit memory hole. This setting must be
enabled.
If there is no setting for MTRR mapping or 32 bit memory hole, contact your
system or motherboard vendor and ask how to enable write combining.
You can check and adjust these BIOS settings using the BIOS Setup utility. For
specific instructions, follow the hardware documentation that came with your
system.
QLogic also provides a script, ipath_mtrr, which sets the MTRR registers,
enabling maximum performance from the InfiniPath driver. This Python script is
available as a part of the InfiniPath software download, and is contained in the
infinipath* RPM. It is installed in /bin.
To diagnose the machine, run it with no arguments (as a root user):
# ipath_mtrr
The test results will list any problems, if they exist, and provide suggestions on
what to do.
To fix the MTRR registers, use:
# ipath_mtrr -w
Restart the driver after fixing the registers.
This script needs to be run after each system reboot. It can be set to run
automatically upon restart by adding this line in
/etc/sysconfig/infinipath :
IPATH_MTRR_ACTIVE=1
See the ipath_mtrr(8) man page for more information on other options.
NOTE:
Use ipath_mtrr if you are not using the default PAT mechanism to enable
write combining.