7. Linux Sockets Acceleration (LSA)
NetXen, Inc.
Intelligent NIC Installation and Tuning Guide
37
To offload an application with zero copy enabled, type the following:
./nxoffload -a -z -n <application-name>
.
Zero copy is a way to significantly reduce CPU utilization in the send path for some
applications. Not all applications may benefit from using zero copy, and some
reduction in throughput may be observed. Applications that do well with zero copy are
those that have large write sizes and a large number of individual connections.
7.2.3
nxoffload Caveats
nxoffload has the following caveats:
To add or remove offload rules, nxoffload requires root access
Rules may be added or removed at any time. The addition or removal of a rule,
however, will not affect connections that have already been established. For example,
if the user starts a non-offloaded iperf application and then types
./nxoffload -a -n
iperf
, this instantiation of iperf will NOT be subsequently offloaded. Future
instantiations, however, will be offloaded.
7.3
Running LSA
Once the appropriate rule has been entered into nxoffload, no further user intervention is
required. The offload occurs automatically. The offload statistics can be monitored by
reading the file /proc/net/nx_nic/lsa_x/stats, where 'x' is NetXen card number.
7.4
LSA Statistics
Table 12
lists the different types of LSA statistics, along with the current support status for
each type.
Table 12 LSA Statistics
Name
Description
Status
TCP Statistics
TcpMaxConn
The limit on the total number of TCP connections
the entity can support. In entities where the
maximum number of connections is dynamic, this
object should contain the value -1.
Supported.
TcpActiveOpens
The number of times TCP connections have made
a direct transition to the SYN-SENT state from the
CLOSED state.
Supported.
TcpPassiveOpens
The number of times TCP connections have made
a direct transition to the SYN-RCVD state from the
LISTEN state.
Supported.
TcpAttemptFails
The number of times TCP connections have made
a direct transition to the CLOSED state from either
the SYN-SENT state or the SYN-RCVD state, plus
the number of times TCP connections have made a
direct transition to the LISTEN state from the SYN-
RCVD state.
Supported.
