+ Herbert

On 3/16/2019 7:14 PM, Toke Høiland-Jørgensen wrote:
Felix Fietkau <[email protected]> writes:

When using iTXQ, tx sequence number allocation and statistics are run at
dequeue time. Because of that, it is safe to enable NETIF_F_LLTX, which
allows tx handlers to run on multiple CPUs in parallel.

Cool, didn't know about that flag.

It is water under the bridge as this patch got applied already, but I stumbled upon it just recently and didn't know about that flag either. So I looked for more information about it and found the definition [1], but the comment seemed important enough to send this reply.

        NETIF_F_LLTX_BIT,       /* LockLess TX - deprecated. Please */
                                /* do not use LLTX in new drivers */

Here is the commit that marked it deprecated:

commit e24eb521fbf2a350ce879dfc1d8e56d4ffa2aa22
Author: Christian Borntraeger <[email protected]>
Date:   Tue Sep 25 19:42:02 2007 -0700

    [NET]: note that NETIF_F_LLTX is deprecated

So I am not sure we should really do this in mac80211. Maybe Herbert can comment although it has been over a decade ago.

Regards,
Arend

[1] https://elixir.bootlin.com/linux/latest/source/include/linux/netdev_features.h#L32

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