Matrix Vision BVS CA-GX0 Serie Betriebsanleitung Seite 78

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4 FIRST STEPS
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7. Is the amount of the"Receive Descriptors"(RxDesc) of thenetwork controllerset to
the maximum (generally 2048)?
This amount depends on the MTU. You can get a feeling about values with following
formula (per camera and per network port):
RxDesc >= 1.1
---------------------------------
Example 1: 1500 with 1.6 megapixels
RxDesc >= 1.1
--------------
>= 1170
Example 2: 8192 with 1.6 megapixels
RxDesc >= 1.1
--------------
>= 214
NOTE
Both examples are showing the RxDesc values based on packag-
es per image per second. Now, if you increase the images per
second you will see that you reach the amount of "Receive De-
scriptors" very soon. Usually, the default values of the system are
between 64 and 256 and as a general rule too low. Also each use
of a "Receive Descriptor" will result in a certain amount of CPU
time needed, which is why larger packets result in a better overall
performance.
If you are using small MTU values or if there is only a small value
of "Receive Descriptors" possible, you have to enable "Interrupt
Throttling". Interrupt throttling enables the network controller to
combine packets thus lowering the amount of interrupts.
The "Receive Descriptors" a.k.a. "Receive Buffers" (Intel
PRO/1000 network interface) can be found under "Performance
Options":
* PixelPerImg * BytesPerPixel
MTU
* 1.6M * 1
1500
* 1.6M * 1
8192
30