netdev - RE: [PATCH v8 06/11] net/mlx4_en: add page recycle to prepare rx ring for tx support

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Date:	Tue, 12 Jul 2016 12:09:56 +0000
From:	Tariq Toukan <tariqt@...lanox.com>
To:	Brenden Blanco <bblanco@...mgrid.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	Jamal Hadi Salim <jhs@...atatu.com>,
	Saeed Mahameed <saeedm@....mellanox.co.il>,
	Martin KaFai Lau <kafai@...com>,
	"Jesper Dangaard Brouer" <brouer@...hat.com>,
	Ari Saha <as754m@....com>,
	"Alexei Starovoitov" <alexei.starovoitov@...il.com>,
	Or Gerlitz <gerlitz.or@...il.com>,
	"john.fastabend@...il.com" <john.fastabend@...il.com>,
	"hannes@...essinduktion.org" <hannes@...essinduktion.org>,
	Thomas Graf <tgraf@...g.ch>, Tom Herbert <tom@...bertland.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Tariq Toukan <ttoukan.linux@...il.com>
Subject: RE: [PATCH v8 06/11] net/mlx4_en: add page recycle to prepare rx ring
 for tx support

>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@...mgrid.com>

Reviewed-by: Tariq Toukan <tariqt@...lanox.com>