On 6/5/2021 7:34 PM, Matteo Croce wrote:
On Sat, Jun 5, 2021 at 6:06 PM David Ahern <dsahern@xxxxxxxxx> wrote:
On 6/4/21 2:42 AM, Ilias Apalodimas wrote:
[...]
+ /* Driver set this to memory recycling info. Reset it on recycle.
+ * This will *not* work for NIC using a split-page memory model.
+ * The page will be returned to the pool here regardless of the
+ * 'flipped' fragment being in use or not.
+ */
I am not sure I understand how does the last part of comment related
to the code below, as there is no driver using split-page memory model
will reach here because those driver will not call skb_mark_for_recycle(),
right?
Yes the comment is there to prohibit people (mlx5 only actually) to add the
recycling bit on their driver. Because if they do it will *probably* work
but they might get random corrupted packets which will be hard to debug.
What's the complexity for getting it to work with split page model?
Since 1500 is the default MTU, requiring a page per packet means a lot
of wasted memory.
We could create a new memory model, e.g. MEM_TYPE_PAGE_SPLIT, and
restore the behavior present in the previous versions of this serie,
which is, save xdp_mem_info in struct page.
As this could slightly impact the performances, this can be added in a
future change when the drivers which are doing it want to use this
recycling api.
page-split model doesn't only help reduce memory waste, but increase
cache-locality, especially for aggregated GRO SKBs.
I'm looking forward to integrating the page-pool SKB recycling API into
mlx5e datapath. For this we need it to support the page-split model.
Let's see what's missing and how we can help making this happen.
Regards,
Tariq
