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Cc: freebsd-net@freebsd.org
Subject: Re: dummynet dropping too many packets
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Robert Watson wrote:
> 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.
> 
In dev/bce/if_bcereg.h:
#define TX_PAGES        2
#define TOTAL_TX_BD_PER_PAGE  (BCM_PAGE_SIZE / sizeof(struct tx_bd))
#define USABLE_TX_BD_PER_PAGE (TOTAL_TX_BD_PER_PAGE - 1)
#define TOTAL_TX_BD (TOTAL_TX_BD_PER_PAGE * TX_PAGES)
#define USABLE_TX_BD (USABLE_TX_BD_PER_PAGE * TX_PAGES)
#define MAX_TX_BD (TOTAL_TX_BD - 1)

meaning that ifq_drv_maxlen is expected to end up smaller than 
MAX_TX_BD. What if MAX_TX_BD is itself way smaller than 1024?