netdev - Re: [PATCH 4/6 bfp-next] Simplify AF_XDP umem allocation path for Intel drivers.

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Date:   Thu, 27 Jun 2019 19:36:42 -0700
From:   "Jonathan Lemon" <jonathan.lemon@...il.com>
To:     "Jakub Kicinski" <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, bjorn.topel@...el.com,
        magnus.karlsson@...el.com, saeedm@...lanox.com,
        maximmi@...lanox.com, brouer@...hat.com, kernel-team@...com
Subject: Re: [PATCH 4/6 bfp-next] Simplify AF_XDP umem allocation path for
 Intel drivers.

On 27 Jun 2019, at 15:42, Jakub Kicinski wrote:

> On Thu, 27 Jun 2019 15:08:34 -0700, Jonathan Lemon wrote:
>> Now that the recycle stack is always used for the driver umem path, the
>> driver code path can be simplified.
>>
>> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>
>
> I guess it's a question to Bjorn and Magnus whether they want Intel
> drivers to always go through the reuse queue..

I did pass this by them earlier.

> Could you be more explicit on the motivation?  I'd call this patch set
> "make all drivers use reuse queue" rather than "clean up".

The motivation is to have packets which were received on a zero-copy
AF_XDP socket, and which returned a TX verdict from the bpf program,
queued directly on the TX ring (if they're in the same napi context).

When these TX packets are completed, they are placed back onto the
reuse queue, as there isn't really any other place to handle them.

It also addresses Maxim's concern about having buffers end up sitting
on the rq after a ring resize.

I was going to send the TX change out as part of this patch, but
figured it would be better split unto its own series.

> Also when you're changing code please make sure you CC the author.

Who did I miss?
-- 
Jonathan