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Subject: [OMPI users] Excessive Use of CPU System Resources with OpenMPI 1.2.4 using TCP only ..
From: Graham Jenkins (Graham.Jenkins_at_[hidden])
Date: 2008-01-22 00:48:32


We've observed an excessive use of CPU system resources with OpenMPI
1.2.4 using TCP connections only on our SL5 x86_64 Cluster. Typically,
for a simple Canonical Ring Program, we're seeing between 30 and 70%
system usage.

Has anybody else noticed this sort of behaviour?
And does anybody have some suggestions for resolving the issue?

Present values we have are:

--
ompi_info --param btl tcp |grep MCA
                 MCA btl: parameter "btl_base_debug" (current value: "0")
                 MCA btl: parameter "btl" (current value: <none>)
                 MCA btl: parameter "btl_base_verbose" (current value: "0")
                 MCA btl: parameter "btl_tcp_if_include" (current value:
"eth0")
                 MCA btl: parameter "btl_tcp_if_exclude" (current value:
"lo")
                 MCA btl: parameter "btl_tcp_free_list_num" (current
value: "8")
                 MCA btl: parameter "btl_tcp_free_list_max" (current
value: "-1")
                 MCA btl: parameter "btl_tcp_free_list_inc" (current
value: "32")
                 MCA btl: parameter "btl_tcp_sndbuf" (current value:
"131072")
                 MCA btl: parameter "btl_tcp_rcvbuf" (current value:
"131072")
                 MCA btl: parameter "btl_tcp_endpoint_cache" (current
value: "30720")
                 MCA btl: parameter "btl_tcp_exclusivity" (current
value: "0")
                 MCA btl: parameter "btl_tcp_eager_limit" (current
value: "65536")
                 MCA btl: parameter "btl_tcp_min_send_size" (current
value: "65536")
                 MCA btl: parameter "btl_tcp_max_send_size" (current
value: "131072")
                 MCA btl: parameter "btl_tcp_min_rdma_size" (current
value: "131072")
                 MCA btl: parameter "btl_tcp_max_rdma_size" (current
value: "2147483647")
                 MCA btl: parameter "btl_tcp_flags" (current value: "122")
                 MCA btl: parameter "btl_tcp_priority" (current value: "0")
                 MCA btl: parameter "btl_base_warn_component_unused"
(current value: "1")
-- 
Graham Jenkins
Senior Software Specialist, eResearch
Monash University
Email: Graham.Jenkins_at_[hidden]
Tel:   +613 9905-5942 (office)   +614 4850-2491 (mobile)