bge(4) sysctl tuneables -- a blast from the past.

[Bruce Evans]

On Tue, 16 Apr 2013, Sepherosa Ziehau wrote:

> On Tue, Apr 16, 2013 at 3:14 PM, Bruce Evans <brde at optusnet.com.au> wrote:
>
>> bge_rx_coal_ticks == 0 && bge_rx_max_coal_bds == 0 might work accidentally
>> if there are enough tx interrupts.  There is also the DEVICE_POLLING
>> mistake.
>> In polling mode, these parameters of course have no effect (Polling mode
>> disables interrupts, and the coal parameters have no effect when interrupts
>> are disabled).
>
> As far as I have tested, coalesce BDs and ticks also control how often
> status block is updated, so it does affect polling(4)

This might explain why polling worked even worse than expected for most
things.  However, I got reduced latency using it (from ~55 usec ping
latency to ~30 usec).  30 usec would be impossible with the default
parameters (normal is an average of at least half of bge_rx_coal_ticks).
Maybe I had the parameters reduced to bge_rx_coal_bds = 1 when I found
30 usec (then bge_rx_coal_ticks doesn't matter).  This is probably what
polling should use.

Bruce