The mlx4 driver by default allocates order-3 pages for the ring to
consume in multiple fragments. When the device has an xdp program, this
behavior will prevent tx actions since the page must be re-mapped in
TODEVICE mode, which cannot be done if the page is still shared.
Start by making the allocator configurable based on whether xdp is
running, such that order-0 pages are always used and never shared.
Since this will stress the page allocator, add a simple page cache to
each rx ring. Pages in the cache are left dma-mapped, and in drop-only
stress tests the page allocator is eliminated from the perf report.
Note that setting an xdp program will now require the rings to be
reconfigured.
Before:
26.91% ksoftirqd/0 [mlx4_en] [k] mlx4_en_process_rx_cq
17.88% ksoftirqd/0 [mlx4_en] [k] mlx4_en_alloc_frags
6.00% ksoftirqd/0 [mlx4_en] [k] mlx4_en_free_frag
4.49% ksoftirqd/0 [kernel.vmlinux] [k] get_page_from_freelist
3.21% swapper [kernel.vmlinux] [k] intel_idle
2.73% ksoftirqd/0 [kernel.vmlinux] [k] bpf_map_lookup_elem
2.57% swapper [mlx4_en] [k] mlx4_en_process_rx_cq
After:
31.72% swapper [kernel.vmlinux] [k] intel_idle
8.79% swapper [mlx4_en] [k] mlx4_en_process_rx_cq
7.54% swapper [kernel.vmlinux] [k] poll_idle
6.36% swapper [mlx4_core] [k] mlx4_eq_int
4.21% swapper [kernel.vmlinux] [k] tasklet_action
4.03% swapper [kernel.vmlinux] [k] cpuidle_enter_state
3.43% swapper [mlx4_en] [k] mlx4_en_prepare_rx_desc
2.18% swapper [kernel.vmlinux] [k] native_irq_return_iret
1.37% swapper [kernel.vmlinux] [k] menu_select
1.09% swapper [kernel.vmlinux] [k] bpf_map_lookup_elem
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
d576acf0a2