Date: Tue, 17 Jul 2001 20:41:19 -0400 From: Sergey Babkin <babkin@bellatlantic.net> To: Julian Elischer <julian@elischer.org> Cc: Soren Kristensen <soren@soekris.com>, Bsdguru@aol.com, hackers@FreeBSD.ORG Subject: Re: NatSemi DP83820 gigE driver kit for 4.2 and 4.3 Message-ID: <3B54DB2F.90621945@bellatlantic.net> References: <Pine.BSF.4.21.0107161836400.84815-100000@InterJet.elischer.org>
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Julian Elischer wrote: > > The proble is that teh ethernet header is 14 bytes so you must choose > to allighn either the whole packet, or the IP header, but you cannot do > both. Hm, it seems to be a waste of CPU time memory bandwidth: only the IP and TCP headers have to be aligned but the payload in most cases will be copied over once again to the user space anyway. So, theoretically speaking, this can be solved at the level of the upper protocols: IP and TCP and UDP and NFS are doing m_pullup() anyway (if neccessary), so a call named like m_pullup_align(mp, len, alignment) can be implemented and used instead of m_pullup() to both ensure the minimal length of the buffer chunk and its proper alignment. The difficult thing in such an implementation will be to make sure that all the protocols have been updated to use it. -SB > On Mon, 16 Jul 2001, Soren Kristensen wrote: > > > Hi, > > > > Bsdguru@aol.com wrote: > > > > > > In a message dated 07/16/2001 1:11:09 PM Eastern Daylight Time, > > > tlambert2@mindspring.com writes: > > > > > > > > How do these perform compared to the more expensive gigabit cards? > > > > > > > > Read the driver. > > > > > > > > In general, they require an extra copy because of the inability > > > > of the card to DMA on a reasonable boundry. > > > > > > > > Bill's commentary in his drivers is frequently enlightening, > > > > and often amusing... 8-). To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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