Product specifications

5–Using QLogic MPI
Performance Tuning
IB6054601-00 H 5-21
A
To keep remote process checks but disable triggering quiescence for temporary
IB link failures, use the -disable-mpi-progress-check option with a
nonzero -q option. To disable quiescence triggering altogether, use -q 0. No
matter how these options are used, link failures (temporary or other) are always
logged to syslog.
If the link is down when the job starts and you want the job to continue blocking
until the link comes up, use the -t -1 option.
Performance Tuning
These methods may be used at runtime. Performance settings that are typically
set by the system administrator are listed in “Performance Settings and
Management Tips” on page 4-22.
Use sysctl to Configure Kernel Parameters
sysctl modifies kernel parameters at runtime. You can use the following
parameters to get better TCP/IPoIB performance; QLogic recommends that you
use all of them. Run /sbin/sysctl (as a root user):
# sysctl net.ipv4.tcp_low_latency=0
# sysctl net.ipv4.tcp_timestamps=0
# sysctl net.ipv4.tcp_sack=0
# sysctl net.ipv4.tcp_rmem=’4096 87380 8475988’
# sysctl net.ipv4.tcp_wmem=’4096 65536 8454144’
# sysctl net.ipv4.tcp_mem=’786432 1048576 1572864’
# sysctl net.ipv4.tcp_max_syn_backlog=3000
# sysctl net.core.rmem_max=8475988
# sysctl net.core.wmem_max=8454144
# sysctl net.core.rmem_default=524287
# sysctl net.core.wmem_default=524287
# sysctl net.core.optmem_max=524287
# sysctl net.core.netdev_max_backlog=3000
These settings are in effect until the next reboot. If you want the settings to take
effect on every reboot, add them at the end of the /etc/sysctl.conf file.
CPU Affinity
InfiniPath attempts to run each node program with CPU affinity set to a separate
logical processor, up to the number of available logical processors. If CPU affinity
is already set (with sched_setaffinity() or with the taskset utility), then
InfiniPath will not change the setting.
NOTE:
The sysctl tuning is not necessary for kernel versions 2.6.18 or higher.