09-17-2011
poll is waiting on the socket to get something sent to it. If there are a lot of waits, there can be a network latency issue. Usually I suspect the code as the culprit first, then look at the network.
And yes, if you routinely have 1+ second waits on receiving data, then something somewhere is way wrong.
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LEARN ABOUT CENTOS
rstream
RSTREAM(1) librdmacm RSTREAM(1)
NAME
rstream - streaming over RDMA ping-pong test.
SYNOPSIS
rstream [-s server_address] [-b bind_address] [-B buffer_size]
[-I iterations] [-C transfer_count]
[-S transfer_size] [-p server_port] [-T test_option]
DESCRIPTION
Uses the streaming over RDMA protocol (rsocket) to connect and exchange data between a client and server application.
OPTIONS
-s server_address
The network name or IP address of the server system listening for connections. The used name or address must route over an RDMA
device. This option must be specified by the client.
-b bind_address
The local network address to bind to.
-B buffer_size
Indicates the size of the send and receive network buffers.
-I iterations
The number of times that the specified number of messages will be exchanged between the client and server. (default 1000)
-C transfer_count
The number of messages to transfer from the client to the server and back again on each iteration. (default 1)
-S transfer_size
The size of each send transfer, in bytes. (default 1000) If 'all' is specified, rstream will run a series of tests of various
sizes.
-p server_port
The server's port number.
-T test_option
Specifies test parameters. Available options are:
s | socket - uses standard socket calls to transfer data
a | async - uses asynchronous operation (e.g. select / poll)
b | blocking - uses blocking calls
f | fork - fork server processing (forces -T s option)
n | nonblocking - uses non-blocking calls
v | verify - verifies data transfers
NOTES
Basic usage is to start rstream on a server system, then run rstream -s server_name on a client system. By default, rstream will run a
series of latency and bandwidth performance tests. Specifying a different iterations, transfer_count, or transfer_size will run a user
customized test using default values where none have been specified.
Because this test maps RDMA resources to userspace, users must ensure that they have available system resources and permissions. See the
libibverbs README file for additional details.
SEE ALSO
rdma_cm(7)
librdmacm 2011-11-16 RSTREAM(1)