Endace DAG 3.7D, User Manual

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EDM01-06: DAG 3.7D Card User Guide
©2006 15 Version 1: March 2006
Chapter 4:
Running Data Capture Software
Starting a
Capture
Session
The various tools used for data capture are in the
tools
sub-directory.
For a typical measurement session follow the following steps:
•
First move to the
dag
directory,
•
Load the driver,
•
Then load the appropriate Xilinx receive image to each DAG card. For
example, with the DAG 3.7D card installed:
dagrom –ryvp –f xilinx/dag37dpci_erf.bi
t
The integrity of the card’s physical layer is then set and the integrity of the
physical layer to both DAG cards checked.
Follow the process below to set a data capture session:
•
Set and check integrity of card physical layer. For example:
dagthree –d0 dag0 default
•
Start capture sesson using:
tools/dagsnap d0 –v -o tracefile
Note: The option
-v
is used to provide user information during
capture; it may be wanted to omit it for automated trace runs. If the
–o tracefile
parameter is not specified the tool will write to
stdout
, which can be used to pipeline
dagsnap
with other tools
from the
dagtools
package.
By default
dagsnap
will run indefinitely but can be stopped using ctrl+C .
You can also configure dagsnap to run for a fixed number of seconds then
exit.
High Load
Performance
Overview
As the DAG 3.7D card captures packets from the network link, it writes a
record for each packet into a large buffer in the host PC’s main memory.
Avoiding packet Loss
To avoid packet loss, the user application reading the record, such as
dagsnap
, must be able to read records out of the buffer faster than they
arrive, otherwise the buffer eventually fills, and packet records are lost.
When the PC buffer fills, the message
kernel: dagN: pbm safety
net reached 0xNNNNNNNN
is displayed on the PC screen, and
printed to log
/var/log/messages.
The “Data capture” LED also
goes out. This may be visibly indicated as flashing or flickering.