I understand a bit of Eth and skb code of linux. One of my concerns
was interrupts.
In this case, the system can potentially be interrupted too
often(assuming an interrupt per frame received and transmitted,
it comes to nearly interrupt every few 10s of uSecs). So, though the
packet processing doesnt take much time(involving movement of skbs
and modifying few fields), there is a hidden cost of context
swaps(kernel isr, bh, user space)
I am not sure of the effect of this on performance..
thanx
gopi
On Fri, 31 Jan 2003, Allen Curtis wrote:
quoted
interfaces: hdlc interfaces (external hdlc controller connected
to 8260 which
can write to SDRAM directly. Hence 8260 wont be
involved in packet copying).
routing:
+------------+
Ethernet | 8260 based |hdlc
External world <===========> | embedded |----- 40 systems
| system |-----
| |-----
+------------+
As you can see, the systems on hdlc are connected to external world
through the 8260 based embedded system.
At peak, 8260 will have to get/send of all the hdlc interfaces and
route them to external world over Ethernet.
The only processor overhead you should have is inspecting the HDLC packets
and repackaging them for routing purposes. Take some time and learn the
Ethernet and SKB portions of Linux. You should be able to preallocate all
your buffers. The HDLC ASIC will DMA into RAM, the 8260 will DMA out the
Ethernet packets. Achievable CPU utilization should be very low.
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