Date: Tue, 11 Mar 1997 02:24:01 -0800 From: David Greenman <dg@root.com> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: msmith@atrad.adelaide.edu.au (Michael Smith), bde@zeta.org.au, bag@sinbin.demos.su, hackers@freebsd.org Subject: Re: performance (was: 100 Mb/s cards) Message-ID: <199703111024.CAA19472@root.com> In-Reply-To: Your message of "Tue, 11 Mar 1997 10:24:13 %2B0100." <199703110924.KAA29182@labinfo.iet.unipi.it>
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>For incoming data, a bit of care in the allocation of buffers is >probably necessary (so that the ethernet header goes into a separate >mbuf). I have no idea if any of our drivers does this, but probably it >would be a nice thing to have. > >David, do you know something about this ? The de driver doesn't copy the packet unless it's being compiled on an Alpha. Both the de and fxp drivers DMA the packet with the ethernet header aligned on a 32bit boundry, which means that the packet minus the ether header is not 32bit aligned (only 16bit alignment). Due to the architecture of the DC21x4x, it's not possible to work around this. It is possible to use different alignment with the Pro/100B chip (82557), but I don't currently do that in the driver - it was easier not to bother. I might change this in the future. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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