netdev - Re: [PATCH bpf-next] libbpf: add xsk_ring_prod_

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Date:   Mon, 24 Jun 2019 11:37:40 +0200
From:   "Eelco Chaudron" <echaudro@...hat.com>
To:     "Andrii Nakryiko" <andrii.nakryiko@...il.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>
Cc:     Networking <netdev@...r.kernel.org>,
        "Alexei Starovoitov" <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        "Martin Lau" <kafai@...com>, "Song Liu" <songliubraving@...com>,
        "Yonghong Song" <yhs@...com>
Subject: Re: [PATCH bpf-next] libbpf: add xsk_ring_prod__free() function



On 21 Jun 2019, at 21:13, Andrii Nakryiko wrote:

> On Fri, Jun 21, 2019 at 8:26 AM Eelco Chaudron <echaudro@...hat.com> 
> wrote:
>>
>> When an AF_XDP application received X packets, it does not mean X
>> frames can be stuffed into the producer ring. To make it easier for
>> AF_XDP applications this API allows them to check how many frames can
>> be added into the ring.
>>
>> Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
>> ---
>>  tools/lib/bpf/xsk.h | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
>> index 82ea71a0f3ec..86f3d485e957 100644
>> --- a/tools/lib/bpf/xsk.h
>> +++ b/tools/lib/bpf/xsk.h
>> @@ -95,6 +95,12 @@ static inline __u32 xsk_prod_nb_free(struct 
>> xsk_ring_prod *r, __u32 nb)
>>         return r->cached_cons - r->cached_prod;
>>  }
>>
>> +static inline __u32 xsk_ring_prod__free(struct xsk_ring_prod *r)
>
> This is a very bad name choice. __free is used for functions that free
> memory and resources. One function below I see avail is used in the
> name, why not xsk_ring_prog__avail?

Must agree that free sound like you are freeing entries… However, I 
just kept the naming already in the API/file (see above, 
xsk_prod_nb_free()).
Reading the code there is a difference as xx_avail() means available 
filled entries, where xx_free() means available free entries.

So I could rename it to xsk_ring_prod__nb_free() maybe?

Forgot to include Magnus in the email, so copied him in, for some 
comments.

>> +{
>> +       r->cached_cons = *r->consumer + r->size;
>> +       return r->cached_cons - r->cached_prod;
>> +}
>> +
>>  static inline __u32 xsk_cons_nb_avail(struct xsk_ring_cons *r, __u32 
>> nb)
>>  {
>>         __u32 entries = r->cached_prod - r->cached_cons;
>> --
>> 2.20.1
>>