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From: Ilija Kocho <>
	 eCos developers <>
Subject: Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?
Date: Tue, 07 Jun 2011 08:55:00 -0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 07.06.2011 04:18, Laurie Gellatly wrote:
> On 07/06/2011, at 10:57 AM, Grant Edwards <> wrote:
>> On 2011-06-07, Laurie Gellatly <> 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:
>> and search the list archive:
> 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?


           reply	other threads:[~2011-06-07  8:55 UTC|newest]

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
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