Re: [PATCH v3 net-next 08/14] mlx4: use order-0 pages for RX

On Tue, Feb 14, 2017 at 10:46 AM, Jesper Dangaard Brouer
[off-list ref] wrote:

With this Intel driver page count based recycle approach, the recycle
size is tied to the size of the RX ring.  As Eric and Tariq discovered.
And for other performance reasons (memory footprint of walking RX ring
data-structures), don't want to increase the RX ring sizes.  Thus, it
create two opposite performance needs.  That is why I think a more
explicit approach with a pool is more attractive.

How is this approach doing to work for XDP?
(XDP doesn't "share" the page, and in-general we don't want the extra
atomic.)

We absolutely need recycling with XDP, when transmitting out another
device, and the other devices DMA-TX completion need some way of
returning this page.
What is basically needed is a standardized callback to allow the remote
driver to return the page to the originating driver.  As we don't have
a NDP for XDP-forward/transmit yet, we could pass this callback as a
parameter along with the packet-page to send?

mlx4 already has a cache for XDP.
I believe I did not change this part, it still should work.

commit d576acf0a22890cf3f8f7a9b035f1558077f6770
Author: Brenden Blanco [off-list ref]
Date:   Tue Jul 19 12:16:52 2016 -0700

    net/mlx4_en: add page recycle to prepare rx ring for tx support

I have not checked if recent Tom work added core infra for this cache.

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