netdev - Re: [PATCH v3 net-next 08/14] mlx4: use order-0 pages for RX

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Date:   Mon, 13 Feb 2017 15:26:22 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Saeed Mahameed <saeedm@...lanox.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 v3 net-next 08/14] mlx4: use order-0 pages for RX

On Mon, Feb 13, 2017 at 3:22 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> On Mon, Feb 13, 2017 at 3:16 PM, Alexander Duyck
> <alexander.duyck@...il.com> wrote:
>
>> Any plans to add the bulk page count updates back at some point?  I
>> just got around to adding it for igb in commit bd4171a5d4c2 ("igb:
>> update code to better handle incrementing page count").  I should have
>> patches for ixgbe, i40e, and i40evf here pretty soon.  That was one of
>> the reasons why I implemented __page_frag_cache_drain in the first
>> place.  As I'm sure Jesper will probably point out the atomic op for
>> get_page/page_ref_inc can be pretty expensive if I recall correctly.
>
> As a matter of fact I did this last week, but could not show any
> improvement on one TCP flow,
> so decided to not include this in this patch series.
>
> Maybe the issue was more a sender issue, I might revisit this later.

Odds are for a single TCP flow you won't notice.  This tends to be
more of a small packets type performance issue.  If you hammer on he
Rx using pktgen you would be more likely to see it.

Anyway patch looks fine from a functional perspective so I am okay
with it.  The page count bulking is something that can be addressed
later.

Thanks.

- Alex