dummynet dropping too many packets

[Julian Elischer]

rihad wrote:
> Robert Watson wrote:
> 
>> I would suggest making just the HZ -> 4000 change for now and see how 
>> it goes.
>>
> OK, I will try testing HZ=4000 tomorrow morning, although I'm pretty 
> sure there still will be some drops.
> 
>>> Can someone please say how to increase the "ifnet transmit queue sizes"?
>>
>> Unfortunately, I fear that this is driver-specific, and in the case of 
>> bce requires a recompile.  In the driver init code in if_bce, the 
>> following code appears:
>>
>>         ifp->if_snd.ifq_drv_maxlen = USABLE_TX_BD;
>>         IFQ_SET_MAXLEN(&ifp->if_snd, ifp->if_snd.ifq_drv_maxlen);
>>         IFQ_SET_READY(&ifp->if_snd);
>>
>> Which evaluates to a architecture-specific value due to varying 
>> pagesize.  You might just try forcing it to 1024.
>>
> I think I'll try this too, if HZ=4000 doesn't help, thanks a lot.
> In the long run we'll switch to some high-quality 10 GiGE cards.

for output..

It may still be possible for the output queues to be overrun as teh 
bursts from dummynet can be much faster than even 10G hardware can 
dispose of the data.