From: Lorenzo Bianconi <lorenzo@kernel•org>
To: Saeed Mahameed <saeed@kernel•org>
Cc: bpf@vger•kernel.org, netdev@vger•kernel.org, davem@davemloft•net,
kuba@kernel•org, ast@kernel•org, daniel@iogearbox•net,
brouer@redhat•com, lorenzo.bianconi@redhat•com,
alexander.duyck@gmail•com, maciej.fijalkowski@intel•com
Subject: Re: [PATCH v2 bpf-next 2/2] net: xdp: introduce xdp_prepare_buff utility routine
Date: Sat, 12 Dec 2020 15:34:27 +0100 [thread overview]
Message-ID: <20201212143427.GA180288@lore-desk> (raw)
In-Reply-To: <59bc3e140cfb859bb8451a1e87da5125b956d778.camel@kernel.org>
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On Dec 11, Saeed Mahameed wrote:
> On Fri, 2020-12-11 at 20:28 +0100, Lorenzo Bianconi wrote:
> > Introduce xdp_prepare_buff utility routine to initialize per-
> > descriptor
> > xdp_buff fields (e.g. xdp_buff pointers). Rely on xdp_prepare_buff()
> > in
> > all XDP capable drivers.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel•org>
> >
> ...
> > +static inline void
> > +xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
> > + int headroom, int data_len)
> > +{
> > + xdp->data_hard_start = hard_start;
> > + xdp->data = hard_start + headroom;
> > + xdp->data_end = xdp->data + data_len;
> > + xdp->data_meta = xdp->data;
>
> You might want to compute data = hard_start + headroom; on a local var,
> and hopefully gcc will put it into a register, then reuse it three
> times instead of the 2 xdp->data de-references you got at the end of
> the function.
>
> unsigned char *data = hard_start + headroom;
>
> xdp->data_hard_start = hard_start;
> xdp->data = data;
> xdp->data_end = data + data_len;
> xdp->data_meta = data;
ack, I will fix it in v3.
Regards,
Lorenzo
>
>
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prev parent reply other threads:[~2020-12-12 14:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-11 19:28 [PATCH v2 bpf-next 0/2] introduce xdp_init_buff/xdp_prepare_buff Lorenzo Bianconi
2020-12-11 19:28 ` [PATCH v2 bpf-next 1/2] net: xdp: introduce xdp_init_buff utility routine Lorenzo Bianconi
2020-12-11 19:28 ` [PATCH v2 bpf-next 2/2] net: xdp: introduce xdp_prepare_buff " Lorenzo Bianconi
2020-12-12 1:00 ` Saeed Mahameed
2020-12-12 14:34 ` Lorenzo Bianconi [this message]
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