Re: [RFC] Removal of M_FLOWID flag from m_flags [WAS: Add support for hardware transmit rate limiting queues]

From: Michael Tuexen <tuexen_at_freebsd.org>
Date: Wed, 19 Nov 2014 20:30:21 +0100
On 19 Nov 2014, at 20:02, Hans Petter Selasky <hps_at_selasky.org> wrote:

> Hi,
> 
> The M_FLOWID flag is marked as deprecated in the FreeBSD kernel code and the patch below completely removes it. I suggest we will now be using the "m_pkthdr.rsstype" also known as "M_HASHTYPE" to decide if the flowid value is valid or not. When the "rsstype" is set to "M_HASHTYPE_NONE" the "m_pkthdr.flowid" field is not valid. Else this field contains valid data for both TX and RX direction.
> 
> Background:
> ===========
> 
> The network drivers today use the "rsstype" field only when receiving traffic. After my patch it is also used when sending traffic, and probably we should rename it.
> 
> The reason for using the rsstype field for transmit, is to avoid introducing another field in the MBUF's packet header in order to steer outgoing traffic into special multiple purpose hardware FIFOs. This new feature should coexist with the existing flowid mechanism, and this is achieved by introducing a new hash type which I've named "M_HASHTYPE_HWRING" in my patch. This type can be selected by upper layers when generating traffic for lower layers, to indicate that the traffic is of a special kind and should have special treatment by the hardware, like rate-limiting. Hardware which doesn't support M_HASHTYPE_HWRING will send out the packets like usual.
> 
> 
> Patch is available from here:
> =============================
> http://home.selasky.org:8192/m_flowid_removal.diff
> 
> 
> Comments are appreciated!
Before finally committing this, drop me a note. All the SCTP changes need to be ported upstream.
Depending on the time and if it is OK for you, I would try to integrate this upstream and push
it down to FreeBSD. Then you can commit the rest. This is simpler for me than reintegrating your
changes upstream...

Best regards
Michael
> 
> 
> --HPS
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Received on Wed Nov 19 2014 - 18:30:27 UTC

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