Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?
On 07.06.2011 04:18, Laurie Gellatly wrote:
> On 07/06/2011, at 10:57 AM, Grant Edwards <[hidden email]> wrote:
>> On 2011-06-07, Laurie Gellatly <[hidden email]> wrote:
>>> I tried to enable this before without success.
>> Ah yes, I saw your (unanswered) post from a few years back asking
>> about this. I was hoping there had been some progress since then.
>>> I agree that its a waste of processor time when it can be performed
>>> in hardware.
>> The last time I did some profiling, IP checksum calculation was a
>> pretty significant bottleneck for TCP throughput. Back in the NetBSD
>> stack days, I got about a 20% improvement in throughput by writing my
>> own assembly-language IP checksum routine for ARM7. The FreeBSD C
>> implementation and more recent versions of gcc do almost as well as
>> hand-tuned assembly, but it's still a big percentage of CPU usage in
>> TCP communications -- and it will be even worse now that I have a chip
>> that does scatter-gather DMA. A part for US $4 that has IP checksum
>> offloading and scatter-gather DMA. Back when I was a new grad...
>>> Must we look at the latest BSD code to see how to implement this?
>> Maybe. Or there might be a simpler way to do it. I would guess that
>> the current FreeBSD has an API to configure this on a per-interface
>> basis at run-time.
>> If we can assume that there is only one external interface, then we
>> don't need any API or runtime checks, just a few strategic #if/#endif
>> pairs and some CDL to control them.
>> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos >> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss >>
> So how do we progress this?
> Should we offline exchange the mods we've each tried (code and CDL)?
I am going to need the same soon only with lwIP. Recent on-chip Ethernet
controllers provide for some IP processing so IMO we should address this
issue generally. Is there place for some community project?