Subject: Re: Ethernet frame padding changes
To: None <firstname.lastname@example.org>
From: David Laight <email@example.com>
Date: 07/07/2004 00:15:06
> > There's no absolute guarantee of that, but that doesn't prevent making the
> > common case optimal.
> I'm not sure it would be more efficient. Even for small packets, you may have
> a mbuf chain (and this may be the common case, in fact).
If a small packet is in a long mbuf chain it could easily be a 'win' to copy
the fragments into a single buffer (of some form). Indeed the 'gather'
DMA may not be also to copy with a large number of small fragments (due to
bus loading reading the descriptors) even if you have reserved enough
space for a descriptor per byte.
I have seen a sytem where an ethernet driver was given a 1500 byte message
that was in over 1400 fragments...
(and if it dropped it, the same packet would be presented again)
David Laight: firstname.lastname@example.org