Re: Re: How to use IP/UDP/TCP checksum offload HW?
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On 07.06.2011 04:18, Laurie Gellatly wrote: > > On 07/06/2011, at 10:57 AM, Grant Edwards <grant.b.edwards@xxxxxxxxx> wrote: > >> On 2011-06-07, Laurie Gellatly <laurie.gellatly@xxxxxxxxx> 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. >> >> -- >> Grant >> >> >> -- >> 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? Ilija. -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss