netdev - Re: [PATCH bpf-next v4 8/8] net/mlx5e: Add AF_XDP need

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Message-ID: <FA76BD00-F81D-453D-AB70-BDE6A4E0950E@gmail.com>
Date:   Wed, 14 Aug 2019 08:40:00 -0700
From:   "Jonathan Lemon" <jonathan.lemon@...il.com>
To:     "Magnus Karlsson" <magnus.karlsson@...el.com>
Cc:     bjorn.topel@...el.com, ast@...nel.org, daniel@...earbox.net,
        netdev@...r.kernel.org, brouer@...hat.com, maximmi@...lanox.com,
        bpf@...r.kernel.org, bruce.richardson@...el.com,
        ciara.loftus@...el.com, jakub.kicinski@...ronome.com,
        xiaolong.ye@...el.com, qi.z.zhang@...el.com,
        sridhar.samudrala@...el.com, kevin.laatz@...el.com,
        ilias.apalodimas@...aro.org, kiran.patil@...el.com,
        axboe@...nel.dk, maciej.fijalkowski@...el.com,
        maciejromanfijalkowski@...il.com, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH bpf-next v4 8/8] net/mlx5e: Add AF_XDP need_wakeup support

On 14 Aug 2019, at 0:27, Magnus Karlsson wrote:

> From: Maxim Mikityanskiy <maximmi@...lanox.com>
>
> This commit adds support for the new need_wakeup feature of AF_XDP. The
> applications can opt-in by using the XDP_USE_NEED_WAKEUP bind() flag.
> When this feature is enabled, some behavior changes:
>
> RX side: If the Fill Ring is empty, instead of busy-polling, set the
> flag to tell the application to kick the driver when it refills the Fill
> Ring.
>
> TX side: If there are pending completions or packets queued for
> transmission, set the flag to tell the application that it can skip the
> sendto() syscall and save time.
>
> The performance testing was performed on a machine with the following
> configuration:
>
> - 24 cores of Intel Xeon E5-2620 v3 @ 2.40 GHz
> - Mellanox ConnectX-5 Ex with 100 Gbit/s link
>
> The results with retpoline disabled:
>
>        | without need_wakeup  | with need_wakeup     |
>        |----------------------|----------------------|
>        | one core | two cores | one core | two cores |
> -------|----------|-----------|----------|-----------|
> txonly | 20.1     | 33.5      | 29.0     | 34.2      |
> rxdrop | 0.065    | 14.1      | 12.0     | 14.1      |
> l2fwd  | 0.032    | 7.3       | 6.6      | 7.2       |
>
> "One core" means the application and NAPI run on the same core. "Two
> cores" means they are pinned to different cores.
>
> Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
> Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
> Reviewed-by: Saeed Mahameed <saeedm@...lanox.com>

Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>