netdev - Re: [PATCH v2 net-next 00/14] mlx4: order-0 allocations and page recycling

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Date:   Thu, 9 Feb 2017 08:44:02 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Tariq Toukan <ttoukan.linux@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v2 net-next 00/14] mlx4: order-0 allocations and page recycling

On Thu, Feb 9, 2017 at 8:41 AM, Tariq Toukan <ttoukan.linux@...il.com> wrote:
> Hi Eric,
>
> Thanks again for your series.
>
> On 09/02/2017 3:58 PM, Eric Dumazet wrote:
>
> As mentioned half a year ago, we better switch mlx4 driver to order-0
> allocations and page recycling.
>
> This reduces vulnerability surface thanks to better skb->truesize
> tracking and provides better performance in most cases.
>
> v2 provides an ethtool -S new counter (rx_alloc_pages) and
> code factorization, plus Tariq fix.
>
> I see that you made significant changes to the previous series, especially
> patch 14 (RX CQE processing).
> Please notice that our work week has just finished here in Israel.
> I will review the series, especially the new patches (10 to 14), on Sunday.
>
> We need to test this series again in our functional and performance
> regression systems.
> It will be running during the weekend, so we can analyze the results and
> update you on Sunday.
>
> Previous performance results showed a degradation, especially in:
> - TCP single stream at 64KB length.

What RX ring size are you using ? I have not seen this at all.

> - TCP 16 streams at 1KB length.

TCP does not really care, it coalesces all these into TSO skbs, full size...

>
> This was probably because cache was too short, and many page allocations
> were needed.
> In CX4, we saw the same kind of degradation, much clearer and amplified as
> it's 2.5 times faster (100G).
>
> Regards,
> Tariq Toukan