Product specifications

4–InfiniPath Cluster Setup and Administration
Performance Settings and Management Tips
IB6054601-00 H 4-23
A
 Use a PCIe Max Read Request size of at least 512 bytes with the
QLE7240 and QLE7280. QLE7240 and QLE7280 adapters can support
sizes from 128 bytes to 4096 byte in powers of two. This value is typically
set by the BIOS.
 Use PCIe Max Payload size of 256, where available, with the QLE7240
and QLE7280. The QLE7240 and QLE7280 adapters can support 128, 256,
or 512 bytes. This value is typically set by the BIOS as the minimum value
supported both by the PCIe card and the PCIe root complex.
 Make sure that write combining is enabled. The x86 Page Attribute Table
(PAT) mechanism that allocates Write Combining (WC) mappings for the
PIO buffers has been added and is now the default. If PAT is unavailable or
PAT initialization fails for some reason, the code will generate a message in
the log and fall back to the MTRR mechanism. See “Write Combining” on
page E-1 for more information.
 Check the PCIe bus width. If slots have a smaller electrical width than
mechanical width, lower than expected performance may occur. Use this
command to check PCIe Bus width:
$ ipath_control -iv
This command also shows the link speed.
Remove Unneeded Services
The cluster administrator can enhance application performance by minimizing the
set of system services running on the compute nodes. Since these are presumed
to be specialized computing appliances, they do not need many of the service
daemons normally running on a general Linux computer.
Following are several groups constituting a minimal necessary set of services.
These are all services controlled by chkconfig. To see the list of services that
are enabled, use the command:
$ /sbin/chkconfig --list | grep -w on
Basic network services are:
 network
 ntpd
 syslog
 xinetd
 sshd
For system housekeeping, use:
 anacron
 atd
 crond