mlx4: allow order-0 memory allocations in RX path

mlx4: allow order-0 memory allocations in RX path

Signed-off-by: Eric Dumazet <[email protected]>
mlx4 exclusively uses order-2 allocations in RX path, which are
likely to fail under memory pressure.

We therefore drop frames more than needed.

This patch tries order-3, order-2, order-1 and finally order-0
allocations to keep good performance, yet allow allocations if/when
memory gets fragmented.

By using larger pages, and avoiding unnecessary get_page()/put_page()
on compound pages, this patch improves performance as well, lowering
false sharing on struct page.

Also use GFP_KERNEL allocations in initialization path, as allocating 12
MB (390 order-3 pages) can easily fail with GFP_ATOMIC.

Signed-off-by: Eric Dumazet <[email protected]>
Cc: Amir Vadai <[email protected]>
Acked-by: Or Gerlitz <[email protected]>
Signed-off-by: David S. Miller <[email protected]>