From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3CDAA320.1050707@embeddededge.com> Date: Thu, 09 May 2002 12:26:08 -0400 From: Dan Malek MIME-Version: 1.0 To: Paul Mackerras Cc: acurtis@onz.com, linuxppc-dev@lists.linuxppc.org Subject: Re: 8260 and skb implementation References: <3CD8BCF7.1090102@embeddededge.com> <15577.52276.175752.518900@argo.ozlabs.ibm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Paul Mackerras wrote: > Doing zero-copy receive requires intelligent adaptor firmware/hardware > that can look in the headers and put the packet in different places > depending on what it finds. ???? > .... Very few adaptors can do this and I > assume the CPM can't. Piece of cake with the CPM.....I just didn't know the Linux protocol stack wanted these separated and where to put them if it did. I can also assemble packets from fragments just as easily. I can even align the headers and data in separate cache lines if you want. When we discuss the 'zero-copy' I assumed (I guess incorrectly) that we DMA directly into the receive SK buffer. In the past on 8xx, we have allocated uncached memory for the CPM receive buffers and then copied into the receive SK buffer. We have to do this because of other data shared by the cache line and the SK buffer. > Cache coherence shouldn't be a problem on transmission .... It never has been and we have always used the sk buffer directly for DMA output. It's always been the ability to properly allocate the sk buffer for the received. In any case, none of this is an issue for the 82xx, which originally started this thread. Thanks. -- Dan ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/