[Beowulf] RHEL5 network throughput/scalability

Walid walid.shaari at gmail.com
Fri Jun 13 12:55:23 PDT 2008

Dear All,

It is lame, however i managed to get the following kernel paramter to scale
well in terms of both performance per node, and scalability over  a high
bandwidth low latency network

net.ipv4.tcp_workaround_signed_windows = 1

net.ipv4.tcp_congestion_control = vegas

net.ipv4.tcp_tso_win_divisor = 8

net.ipv4.tcp_rmem = 4096      87380   174760

net.ipv4.tcp_wmem = 4096      16384   131072

net.ipv4.tcp_mem = 786432     1048576 1572864

net.ipv4.route.max_size = 8388608

net.ipv4.route.gc_thresh = 524288

net.ipv4.icmp_ignore_bogus_error_responses = 0

net.ipv4.icmp_echo_ignore_broadcasts = 0

net.ipv4.tcp_max_orphans = 262144

net.core.netdev_max_backlog = 2000



2008/6/13 Walid <walid.shaari at gmail.com>:

> 2008/6/13 Jason Clinton <jclinton at advancedclustering.com>:
>> We've seen fairly erratic behavior induced by newer drivers for NVidia
>> NForce-based NIC's with forcedeth. If that's your source NIC in the above
>> scenario, that could be the source of the issue as congestion timing has
>> probably changed. Have you tried updating your source NIC driver to
>> whichever is the newest? Nearly all NIC vendors that are incorporated on
>> server motherboards put out updated drivers on their websites.
>> Jason,
> The NIC is broadcom (Bnx2 driver), I have, however i had to go to the
> RHEL5.1 kernel as it does not want to compile on the new kernels. however it
> did not change much, i have also played with the different congestion
> settings, and even though Vegas seems to be the most performance capable,
> it still did not solve it, I had one test that i did not write down where it
> did perform well, I have saved the sysctl and will check what parameters
> have made the difference.
> regards
> Walid
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