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

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Message-ID: <CAKgT0UeB_e_Z7LM1_r=en8JJdgLhoYFstWpCDQN6iawLYZJKDA@mail.gmail.com>
Date:   Mon, 13 Feb 2017 15:16:35 -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 1:09 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> On Mon, Feb 13, 2017 at 12:51 PM, Alexander Duyck
> <alexander.duyck@...il.com> wrote:
>> On Mon, Feb 13, 2017 at 11:58 AM, Eric Dumazet <edumazet@...gle.com> wrote:
>
>>> +                              PAGE_SIZE, priv->dma_dir);
>>>                 page = page_alloc->page;
>>>                 /* Revert changes done by mlx4_alloc_pages */
>>> -               page_ref_sub(page, page_alloc->page_size /
>>> +               page_ref_sub(page, PAGE_SIZE /
>>>                                    priv->frag_info[i].frag_stride - 1);
>>>                 put_page(page);
>>>                 page_alloc->page = NULL;
>>
>> You can probably simplify this by using __page_frag_cache_drain since
>> that way you can just doe the sub and test for the whole set instead
>> of doing N - 1 and 1.
>
> Well, we remove this anyway in following patch ;)

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.

- Alex