[Click] buffersizes

[Wenjun Hu]

A few things to try:

Assuming your wireless interface is called ath0,

ifconfig ath0 txqueuelen 1
ifconfig ath0raw txqueuelen 1 (if you're using the raw device)

Then in if_athvar.h within the madwifi source code, there's a constant called 
ATH_TXBUF that's probably set to 200. That's the default value for txqueuelen 
when you load the driver module. You could reduce this number, but beware that 
it might cause packet (frame) drops on the card if you make it too small.

There's also a linked list structure in the driver (e.g., you'll see 
netif_wake_queue and netif_sleep_queue in a few functions in if_ath.c) that 
contains frames to be sent. You could make sure there's only ever one frame in 
the list (i.e., call sleep queue as soon as one frame is there), but this 
could cause a lot of interrupts, and I'm not sure about the general 
implications for performance.

If your packets will go through some socket buffer in the kernel, then you 
might want to change the size of that too.

There's probably some buffer on the card too, but you probably can't change 
that unless you can access the firmware.

Hope this helps,

Wenjun


> Hello list,
> 
> Not really a Click issue, but maybe you came across the same problem.
> 
> I'm using 2 queues in a script and merge them with a priorityscheduler. The
> high priority queueu will contain L2 management packets (beacons, asso reqs
> etc) while all other traffic will pass the low priority queue.
> 
> The problem I encounter now is that packets will be delivered to the device
> and will be queued there (in the driver/kernel ?) too. So I can only
> prioritize the management packets to a certain extend. I suppose I could
> iptimize things if I could cut the buffers outside of Click to size one,
> thus forcing the FromDevice only to pull from the queue when a packet has
> been send and as a consequence doing all buffering inside click.
> 
> Does anyone know how I could do this? I'm using the madwifi driver , but
> maybe there are also some general kernel networking parameters to change.
> 
> Any suggestions are welcome!
> 
> Peter De Cleyn
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