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

From: K. Macy <kmacy_at_freebsd.org>
Date: Wed, 19 Nov 2014 12:46:05 -0800
Hi Hans,

It mostly looks fine, but it's a large change and there are some
places in the patch where it isn't clear that the right thing is being
done by looking at the patch alone. Please give us some time to
review.


Thanks.

-K

On Wed, Nov 19, 2014 at 11:02 AM, 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!
>
>
> --HPS
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Received on Wed Nov 19 2014 - 19:46:06 UTC

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