Thanks Russell, On 09/23/2016 11:37 AM, Russell King - ARM Linux wrote: > On Fri, Sep 23, 2016 at 11:26:18AM -0700, Eric Nelson wrote: >> So the question is: should we just live with this and acknowledge a >> performance penalty of bad alignment or do something about it? > > Well, I've no interest in trying to do anything with the FEC driver > anymore, as I'll just generate another big patch stack which won't > make it into the kernel in a timely fashion - my last attempt at > improving the FEC driver was dogged with conflicting changes and I > gave up with it in the end. I ended up spending a full cycle > rebasing, re-testing, and re-evaluating their performance only to find > that I'd missed the merge window again, and other conflicting changes > got merged which meant that I had to start from the beginning again. >
That's sad. I recall reading your notes on that patch series and it was a model for how to structure and document a patch set. I hadn't noticed that you abandoned it and it's frustrating that the merge process prevented your efforts from being used. I'm also disheartened to hear your frustration about getting things pushed up-stream and the entire Linux community should take note. >> I'm not sure the cost (or the details) of Eric's proposed fix of allocating >> and copying the header to another skb. > > I had a quick look at this, and although Eric's idea may be a good > idea, it doesn't contain enough details for me to be able to > implement it - eg, I've no idea how to attach the 128-byte skb to the > beginning of a previously allocated skb containing the rest of the > packet. I've just looked through linux/skbuff.h and I can't see > anything that takes two sk_buff's that would do the job. > > However, I don't think that's necessary in this case, because the > iMX6 FEC supports the 16-bit alignment of the packet, if only it was > enabled in hardware and the driver caters for it. > Right. If the hardware supports placing things at a suitable address, that's the right approach. I'll try to review your earlier patch set and at least find a way to address the alignment issues. I'm a bit booked until LinuxCon but will try to get something out soon. Regards, Eric
