[ECOS] How to use IP/UDP/TCP checksum offload HW?

[ECOS] How to use IP/UDP/TCP checksum offload HW?

[Grant Edwards]

How do you tell the eCos network API that IP/TCP/UDP checksumming is
handled by hardware?  I've found the if_data.ifi_hwassist field, but
I'm not positive it really does what I want, and it only seems to
affect the tx side of the stack.

Does if_data.ifi_hwassist tell ip_output.c to skil checkums in tx
packets and let the hardware do it?

How do you tell the rx side of the stack that it doesn't need to check
IP, UDP, and TCP checksums (the hardware will discard any packets with
invalid checksums).

It seems a shame to not support for HW checksum offloading when it's
gotten to the point where even a $4 uController has IP checksum
offloading HW.

-- 
Grant Edwards               grant.b.edwards        Yow! Eisenhower!!  Your
                                  at               mimeograph machine upsets
                              gmail.com            my stomach!!


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Re: [ECOS] How to use IP/UDP/TCP checksum offload HW?

[Laurie Gellatly]

Hi Grant,
I tried to enable this before without success. I agree that its a waste of processor time when it can be performed in hardware. Must we look at the latest BSD code to see how to implement this?

        ...Laurie:{)


On 07/06/2011, at 5:34 AM, Grant Edwards <grant.b.edwards@gmail.com> wrote:

> How do you tell the eCos network API that IP/TCP/UDP checksumming is
> handled by hardware?  I've found the if_data.ifi_hwassist field, but
> I'm not positive it really does what I want, and it only seems to
> affect the tx side of the stack.
> 
> Does if_data.ifi_hwassist tell ip_output.c to skil checkums in tx
> packets and let the hardware do it?
> 
> How do you tell the rx side of the stack that it doesn't need to check
> IP, UDP, and TCP checksums (the hardware will discard any packets with
> invalid checksums).
> 
> It seems a shame to not support for HW checksum offloading when it's
> gotten to the point where even a $4 uController has IP checksum
> offloading HW.
> 
> -- 
> Grant Edwards               grant.b.edwards        Yow! Eisenhower!!  Your
>                                  at               mimeograph machine upsets
>                              gmail.com            my stomach!!
> 
> 
> -- 
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
> 

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[ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Grant Edwards]

On 2011-06-07, Laurie Gellatly <laurie.gellatly@netic.com> 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


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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Laurie Gellatly]

On 07/06/2011, at 10:57 AM, Grant Edwards <grant.b.edwards@gmail.com> wrote:

> On 2011-06-07, Laurie Gellatly <laurie.gellatly@netic.com> 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)?

...Laurie:{)

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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Ilija Kocho]

On 07.06.2011 04:18, Laurie Gellatly wrote:
>
> On 07/06/2011, at 10:57 AM, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>
>> On 2011-06-07, Laurie Gellatly <laurie.gellatly@netic.com> 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.


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[ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Grant Edwards]

On 2011-06-07, Ilija Kocho <ilijak@siva.com.mk> wrote:

>>>> 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.
>>
>> So how do we progress this? Should we offline exchange the mods we've
>> each tried (code and CDL)?

I won't have any hardware available until Q4.  So I probably won't be
ble to spend much time on it for a few months.

> 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?

There are a number of svn/git/hg/whatever hosting sites that could be
used.  IIRC, somebody had set up a site to host eCos-related stuff, I
guess this is it:

  http://ecosx.sourceforge.net/

It doesn't look like it's been touched for 5 years, but the guy who
set it up is still active on other projects on sourceforge.

One question in my mind is whether it needs to be run-time
configurable on a per-interface basis, or can it be a global,
build-time option.

-- 
Grant Edwards               grant.b.edwards        Yow! Don't hit me!!  I'm in
                                  at               the Twilight Zone!!!
                              gmail.com            


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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Jay Foster]

On 6/7/2011 7:41 AM, Grant Edwards wrote:
> On 2011-06-07, Ilija Kocho<ilijak@siva.com.mk>  wrote:
>
>>>>> 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.
>>> So how do we progress this? Should we offline exchange the mods we've
>>> each tried (code and CDL)?
> I won't have any hardware available until Q4.  So I probably won't be
> ble to spend much time on it for a few months.
>
>> 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?
> There are a number of svn/git/hg/whatever hosting sites that could be
> used.  IIRC, somebody had set up a site to host eCos-related stuff, I
> guess this is it:
>
>    http://ecosx.sourceforge.net/
>
> It doesn't look like it's been touched for 5 years, but the guy who
> set it up is still active on other projects on sourceforge.
>
> One question in my mind is whether it needs to be run-time
> configurable on a per-interface basis, or can it be a global,
> build-time option.
>
My view is that it should be either (or both) run-time or CDL 
configurable on a per-interface basis.  When using more than one network 
interface, one cannot assume that the each have the same capabilities.

Jay

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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Ilija Kocho]

On 07.06.2011 16:41, Grant Edwards wrote:
> On 2011-06-07, Ilija Kocho <ilijak@siva.com.mk> wrote:
>
>>>>> 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.
>>> So how do we progress this? Should we offline exchange the mods we've
>>> each tried (code and CDL)?
> I won't have any hardware available until Q4.  So I probably won't be
> ble to spend much time on it for a few months.

I have just started with the driver. My first step is to make plain
driver without acceleration so it will take some time.
But before we start coding there are many questions to answer...

>> 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?
> There are a number of svn/git/hg/whatever hosting sites that could be
> used.  IIRC, somebody had set up a site to host eCos-related stuff, I
> guess this is it:
>
>   http://ecosx.sourceforge.net/
>
> It doesn't look like it's been touched for 5 years, but the guy who
> set it up is still active on other projects on sourceforge.

I guess this is fresher regarding lwIP:
http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
Only it might be stalled. John, is this an active project?

> One question in my mind is whether it needs to be run-time
> configurable on a per-interface basis, or can it be a global,
> build-time option.

We need to raise and resolve a number of questions indeed. What parts of
stack are going to be affected, etc.
Needless to say, device code must work with all (both) stacks that shall
support new features.
It could be that different devices support different (subsets of) IP
features, so I guess some per device configuration shall be necessary.
Regarding run-time configureability I doubt it. It will add complexity +
both memory and performance penalty. Run-time user is (most often) the
end user or her admin).Shall (s)he benefit? Or want to deal with it?

Ilija


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[ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[John Dallaway]

Hi Ilija

Ilija Kocho wrote:

>> It doesn't look like it's been touched for 5 years, but the guy who
>> set it up is still active on other projects on sourceforge.
> 
> I guess this is fresher regarding lwIP:
> http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
> Only it might be stalled. John, is this an active project?

Yes. Simon Kallweit is working on the lwIP 1.4.0 port.

John Dallaway
eCos maintainer
http://www.dallaway.org.uk/john

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RE: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Laurie Gellatly]

Hi Simon,
Are you doing anything about enabling hardware CRC in the new port
that we should align to?

			...Laurie:{)

> -----Original Message-----
> From: ecos-discuss-owner@ecos.sourceware.org [mailto:ecos-discuss-
> owner@ecos.sourceware.org] On Behalf Of John Dallaway
> Sent: Wednesday, 8 June 2011 5:48 AM
> To: Ilija Kocho
> Cc: ecos-discuss@ecos.sourceware.org; Simon Kallweit
> Subject: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?
> 
> Hi Ilija
> 
> Ilija Kocho wrote:
> 
> >> It doesn't look like it's been touched for 5 years, but the guy who
> >> set it up is still active on other projects on sourceforge.
> >
> > I guess this is fresher regarding lwIP:
> > http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
> > Only it might be stalled. John, is this an active project?
> 
> Yes. Simon Kallweit is working on the lwIP 1.4.0 port.
> 
> John Dallaway
> eCos maintainer
> http://www.dallaway.org.uk/john
> 
> --
> Before posting, please read the FAQ:
> http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss


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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Ilija Kocho]

Regarding lwIP we have been knocking on open door.
Look for: CYGPKG_LWIP_CHECKSUMS

Ilija


On 07.06.2011 22:17, Laurie Gellatly wrote:
> Hi Simon,
> Are you doing anything about enabling hardware CRC in the new port
> that we should align to?
>
> 			...Laurie:{)
>
>> -----Original Message-----
>> From: ecos-discuss-owner@ecos.sourceware.org [mailto:ecos-discuss-
>> owner@ecos.sourceware.org] On Behalf Of John Dallaway
>> Sent: Wednesday, 8 June 2011 5:48 AM
>> To: Ilija Kocho
>> Cc: ecos-discuss@ecos.sourceware.org; Simon Kallweit
>> Subject: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?
>>
>> Hi Ilija
>>
>> Ilija Kocho wrote:
>>
>>>> It doesn't look like it's been touched for 5 years, but the guy who
>>>> set it up is still active on other projects on sourceforge.
>>> I guess this is fresher regarding lwIP:
>>> http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
>>> Only it might be stalled. John, is this an active project?
>> Yes. Simon Kallweit is working on the lwIP 1.4.0 port.
>>
>> John Dallaway
>> eCos maintainer
>> http://www.dallaway.org.uk/john
>>
>> --
>> Before posting, please read the FAQ:
>> http://ecos.sourceware.org/fom/ecos
>> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>


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RE: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Laurie Gellatly]

Google only knows of CYGPKG_LWIP_CHECKSUMS in the email you sent.
I suspect it won't be much use to those of us that are using FreeBSD stack
either. Or will it?

			...Laurie:{)

-----Original Message-----
From: ecos-discuss-owner@ecos.sourceware.org
[mailto:ecos-discuss-owner@ecos.sourceware.org] On Behalf Of Ilija Kocho
Sent: Thursday, 7 July 2011 5:18 AM
To: ecos-discuss@ecos.sourceware.org
Subject: Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

Regarding lwIP we have been knocking on open door.
Look for: CYGPKG_LWIP_CHECKSUMS

Ilija


On 07.06.2011 22:17, Laurie Gellatly wrote:
> Hi Simon,
> Are you doing anything about enabling hardware CRC in the new port 
> that we should align to?
>
> 			...Laurie:{)
>
>> -----Original Message-----
>> From: ecos-discuss-owner@ecos.sourceware.org [mailto:ecos-discuss- 
>> owner@ecos.sourceware.org] On Behalf Of John Dallaway
>> Sent: Wednesday, 8 June 2011 5:48 AM
>> To: Ilija Kocho
>> Cc: ecos-discuss@ecos.sourceware.org; Simon Kallweit
>> Subject: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?
>>
>> Hi Ilija
>>
>> Ilija Kocho wrote:
>>
>>>> It doesn't look like it's been touched for 5 years, but the guy who 
>>>> set it up is still active on other projects on sourceforge.
>>> I guess this is fresher regarding lwIP:
>>> http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
>>> Only it might be stalled. John, is this an active project?
>> Yes. Simon Kallweit is working on the lwIP 1.4.0 port.
>>
>> John Dallaway
>> eCos maintainer
>> http://www.dallaway.org.uk/john
>>
>> --
>> Before posting, please read the FAQ:
>> http://ecos.sourceware.org/fom/ecos
>> and search the list archive: 
>> http://ecos.sourceware.org/ml/ecos-discuss
>


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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Ilija Kocho]

Hi John

On 07.06.2011 21:48, John Dallaway wrote:
> Hi Ilija
>
> Ilija Kocho wrote:
>
>>> It doesn't look like it's been touched for 5 years, but the guy who
>>> set it up is still active on other projects on sourceforge.
>> I guess this is fresher regarding lwIP:
>> http://sourceware.org/ml/ecos-devel/2011-05/msg00003.html
>> Only it might be stalled. John, is this an active project?
> Yes. Simon Kallweit is working on the lwIP 1.4.0 port.

Nice news. Thank you.

Ilija

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[ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Grant Edwards]

On 2011-06-07, Laurie Gellatly <laurie.gellatly@netic.com> wrote:

> Hi Simon, Are you doing anything about enabling hardware CRC in the
> new port that we should align to?

Just to clarify, we're talking about the IP 1's compliment checksum,
not the Ethernet CRC, right?

AFAIK, the network stacks all assume the CRC is done in hardware -- or
at least by the driver code. [Yes, I've used controllers where you had
to do the CRC in software.]

-- 
Grant Edwards               grant.b.edwards        Yow! I'm having a BIG BANG
                                  at               THEORY!!
                              gmail.com            


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Re: [ECOS] Re: How to use IP/UDP/TCP checksum offload HW?

[Ilija Kocho]

On 07.06.2011 22:28, Grant Edwards wrote:
> On 2011-06-07, Laurie Gellatly <laurie.gellatly@netic.com> wrote:
>
>> Hi Simon, Are you doing anything about enabling hardware CRC in the
>> new port that we should align to?
> Just to clarify, we're talking about the IP 1's compliment checksum,
> not the Ethernet CRC, right?

Sure. And optionally some other IP (layer 3) processing.

> AFAIK, the network stacks all assume the CRC is done in hardware -- or
> at least by the driver code. [Yes, I've used controllers where you had
> to do the CRC in software.]
>


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