[Fwd: Re: bge Ierr rate increase from 5.3R -> 6.1R]

[Bruce Evans]

On Sun, 31 Dec 2006, Bruce Evans wrote:

> [cc changed from developers to net]
>
> On Wed, 13 Dec 2006, Bruce Evans wrote:
>
>> On Tue, 12 Dec 2006, Doug Barton wrote:
>> 
>>> This guy's first message about this problem was very detailed, and he
>>> seems highly motivated. Anyone want to help him out?
>> 
>> This might be because bge now actually reports error statistics correctly
>> (so the larger counts are correct, or because the fixes in -current
>> aren't all in RELENG_6 (so the larger and smaller counts may both be
>> incorrect).
>
> I now think that this is a bug in mii (brgphy_service()) introduced
> or enlarged since FreeBSD-5.early.  Under loads that can be handled,
> my 5701 often gets a small number of input errors every second, and
> returning immediately from brgphy_service() fixes these.  bge uses the
> same logic as most NIC drivers for mii_tick(), and this is bad for
> interrupt latency, but the problem here seems to be mangling of packets
> and unrelated to interrupt latency (high loads just usually give a
> packet in flight for brgphy_service() to mangle?).

More debugging showed that almost any of the reads of the phy in mii
cause an input error, and the problem is apparently not present in
FreeBSD-5.early because a bug maintaining sc->bge_link causes mii_tick()
to almost never be called.  The bug seems to have been fixed in if_bge.c
1.102.  FreeBSD-5.early also seems to negotiate the link a bit faster
than -current, but still too slowly.

Bruce