netdev - Re: [PATCH v2 bpf-next 3/8] cpumap: formalize map value as a named struct

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Date:   Mon, 22 Jun 2020 11:33:13 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net,
        ast@...nel.org, daniel@...earbox.net, toke@...hat.com,
        lorenzo.bianconi@...hat.com, dsahern@...nel.org, brouer@...hat.com
Subject: Re: [PATCH v2 bpf-next 3/8] cpumap: formalize map value as a named
 struct

On Sat, 20 Jun 2020 00:57:19 +0200
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> As it has been already done for devmap, introduce 'struct bpf_cpumap_val'
> to formalize the expected values that can be passed in for a CPUMAP.
> Update cpumap code to use the struct.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  include/uapi/linux/bpf.h       |  9 +++++++++
>  kernel/bpf/cpumap.c            | 25 +++++++++++++------------
>  tools/include/uapi/linux/bpf.h |  9 +++++++++
>  3 files changed, 31 insertions(+), 12 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 19684813faae..a45d61bc886e 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3774,6 +3774,15 @@ struct bpf_devmap_val {
>  	} bpf_prog;
>  };
>  
> +/* CPUMAP map-value layout
> + *
> + * The struct data-layout of map-value is a configuration interface.
> + * New members can only be added to the end of this structure.
> + */
> +struct bpf_cpumap_val {
> +	__u32 qsize;	/* queue size */
> +};
> +

Nitpicking the comment: /* queue size */
It doesn't provide much information to the end-user.

What about changing it to: /* queue size to remote target CPU */
?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer