netdev - Re: XDP performance regression due to CONFIG

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Date:   Mon, 16 Apr 2018 23:15:50 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "xdp-newbies@...r.kernel.org" <xdp-newbies@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        David Woodhouse <dwmw2@...radead.org>,
        William Tu <u9012063@...il.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: XDP performance regression due to CONFIG_RETPOLINE Spectre V2

On Mon, Apr 16, 2018 at 11:07:04PM +0200, Jesper Dangaard Brouer wrote:
> On X86 swiotlb fallback (via get_dma_ops -> get_arch_dma_ops) to use
> x86_swiotlb_dma_ops, instead of swiotlb_dma_ops.  I also included that
> in below fix patch.

x86_swiotlb_dma_ops should not exist any mor, and x86 now uses
dma_direct_ops.  Looks like you are applying it to an old kernel :)

> Performance improved to 8.9 Mpps from approx 6.5Mpps.
> 
> (This was without my bulking for net_device->ndo_xdp_xmit, so that
> number should improve more).

What is the number for the otherwise comparable setup without repolines?