IL3 User’s Guide
11S-3002B
page 73
Reserving Memory for Fas
M
otion
FasMotion reserves some amount of PC memory when it starts. The default values is 200 “buffers”,
which translates to about 1GB. On systems that have less than the 4GB recommended minimum
installed memory, this value may be too high, while on systems with 6GB or 8GB of installed memory,
the value may be bumped up for better performance. The argument for memory allocation is -n
x,
where
x,
represents the number of buffers (about 5MB each) to be used.
Examples:
To lower the memory allocation to 500MB:
“...\FasMotion\FasMotion.exe” -n 100
To increase memory allocation to 1.5GB
“...\FasMotion\FasMotion.exe” -n 300
Note: 300 buffers is the maximum Windows will allow.
Using Multiple Switches:
If you are adding the -n switch, you will likely be using the -s “stats” switch as well. Multiple switches
may be used, separated only by a space (the order does not matter):
“...\FasMotion\FasMotion.exe” -n 300 -s
In “Figure 7-10: FasMotion Shortcut” notice there are three memory arguments:
“...\FasMotion\FasMotion.exe” -s -n 250 -b 200
The last argument is the backoff parameter.
Changing the “Backoff” Parameter
The -n x buffers are used to store incoming image data before being written to the target drive. This is
done because the target drive will not read at a consistent rate, especially as it deals with file system
overheads and other housekeeping tasks. The drive will tend to get a little behind, then catching up.
If the drive gets too far behind, the system may run out of buffers before it gets caught up. Fas
M
otion
can tell the camera to stop temporarily while the system catches up, but it takes a while for that
message to get to the camera, and there may be quite a few images already in the pipeline when the
message is sent. FasMotion needs to send the message well before it runs out of buffers or it will start
missing packets.
The default backoff is 1/2 the buffer value. If you have designated 200 buffers, the default backoff will
be 100, meaning that when there are fewer than 100 buffers remaining, the system tells the camera
to stop sending data for a while.
On a very fast system that has the packet delay set very low, the system will use its buffers very
quickly, so it may be good to set the backoff to a value higher than the default. An example of the is
the system used for “Table 7-1: Table Stats.txt High-Performance System” on page 72. This system
has 8GB of memory, is a dedicated system for camera downloads, and is operating with a very small
packet delay. Notice that for some of the saves at 512 x 512, the Min (minimum buffers) goes quite
low--one goes all the way down to 18. Had the all of the buffers been exhausted, the system would
have missed frames and lost a lot of time with retries.
One way to avoid this would be to change the packet delay to a higher number. Another way to avoid
this would be to set the buffers up higher (there is plenty of RAM available) and set the backoff higher
as well, so the system has a little more time to recover when it gets a little behind:
“...\FasMotion\FasMotion.exe” -s -n 300 -b 200
