netdev - Re: [PATCH RFC 08/11] net/mlx5e: XDP fast RX drop bpf programs support

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Date:   Wed, 7 Sep 2016 23:55:42 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>
Cc:     iovisor-dev <iovisor-dev@...ts.iovisor.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tom Herbert <tom@...bertland.com>,
        Martin KaFai Lau <kafai@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Rana Shahout <ranas@...lanox.com>
Subject: Re: [PATCH RFC 08/11] net/mlx5e: XDP fast RX drop bpf programs support

On Wed, Sep 7, 2016 at 3:42 PM, Saeed Mahameed <saeedm@...lanox.com> wrote:
> From: Rana Shahout <ranas@...lanox.com>
>
> Add support for the BPF_PROG_TYPE_PHYS_DEV hook in mlx5e driver.
>
> When XDP is on we make sure to change channels RQs type to
> MLX5_WQ_TYPE_LINKED_LIST rather than "striding RQ" type to
> ensure "page per packet".
>
> On XDP set, we fail if HW LRO is set and request from user to turn it
> off.  Since on ConnectX4-LX HW LRO is always on by default, this will be
> annoying, but we prefer not to enforce LRO off from XDP set function.
>
> Full channels reset (close/open) is required only when setting XDP
> on/off.
>
> When XDP set is called just to exchange programs, we will update
> each RQ xdp program on the fly and for synchronization with current
> data path RX activity of that RQ, we temporally disable that RQ and
> ensure RX path is not running, quickly update and re-enable that RQ,
> for that we do:
>         - rq.state = disabled
>         - napi_synnchronize
>         - xchg(rq->xdp_prg)
>         - rq.state = enabled
>         - napi_schedule // Just in case we've missed an IRQ
>
> Packet rate performance testing was done with pktgen 64B packets and on
> TX side and, TC drop action on RX side compared to XDP fast drop.
>
> CPU: Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
>
> Comparison is done between:
>         1. Baseline, Before this patch with TC drop action
>         2. This patch with TC drop action
>         3. This patch with XDP RX fast drop
>
> Streams    Baseline(TC drop)    TC drop    XDP fast Drop
> --------------------------------------------------------------
> 1           5.51Mpps            5.14Mpps     13.5Mpps

This (13.5 M PPS) is less than 50% of the result we presented @ the
XDP summit which was obtained by Rana. Please see if/how much does
this grows if you use more sender threads, but all of them to xmit the
same stream/flows, so we're on one ring. That (XDP with single RX ring
getting packets from N remote TX rings) would be your canonical
base-line for any further numbers.