Date: Wed, 28 Apr 1999 19:41:25 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Bill Paul <wpaul@skynet.ctr.columbia.edu> Cc: Matthew Dillon <dillon@apollo.backplane.com>, hackers@freebsd.org, current@freebsd.org Subject: Re: NFS Patch #8 for current available - new TCP fixes Message-ID: <Pine.BSF.4.05.9904281941040.41254-100000@herring.nlsystems.com> In-Reply-To: <199904281327.JAA29467@skynet.ctr.columbia.edu>
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On Wed, 28 Apr 1999, Bill Paul wrote: > Of all the gin joints in all the towns in all the world, Matthew Dillon > had to walk into mine and say: > > > (fanfair!) > > (Darth Vader's imperial march theme) > > > NFS Patch #8 for -current is now available. This patch fixes serious bugs > > w/ NFS/TCP. Probably not *all* the failure conditions, but hopefully > > most of them. > [...] > > > Neither the 'de' nor the 'xl' ethernet drivers align the packet. The 'xl' > > driver conditionally aligns it for the alpha. Part of the patch fixes > > the 'xl' driver to unconditionally align the packet buffer in order to > > improve NFS performance. I could not do the same for the 'de' driver > > because I am unsure if the dec chipset can handle an unaligned start > > address. > > >From what I can tell, the DEC parts make you specify an RX DMA buffer > address that is longword aligned. There are actually not that many devices > where you're allowed to use arbitrary byte-aligned addresses for receive > buffers (the 3Com XL and Intel 'speedo' chips let you do it, as well as the > ThunderLAN, and the Alteon Tigon NIC; I _think_ the AMD PCnet/LANCE > devices let you do it, but that's about it). > > For parts that don't support arbitrary alignment, you have to copy. > Now, in some of the drivers that I ported to the alpha, I only copied > the first small section of the packet in order to get the IP header > aligned (since failing to do this causes an unaligned access trap in > the IP code). This is faster than copying the entire packet to fix > the alignment, but I'm not sure what effect it has on NFS. > > That said, although I haven't looked too closely at the de driver (it > scares me -- a lot), it should have some sort of gimmick to fix the > packet alignment otherwise it wouldn't work on the alpha. The de driver copies the entire packet. -- Doug Rabson Mail: dfr@nlsystems.com Nonlinear Systems Ltd. Phone: +44 181 442 9037 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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