netdev - Re: [PATCH v2 net-next] net: ethernet: enetc: unlock XDP

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Message-ID: <Y5L4niz1l9ytUsf8@lore-desk>
Date:   Fri, 9 Dec 2022 09:58:06 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, claudiu.manoil@....com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, lorenzo.bianconi@...hat.com
Subject: Re: [PATCH v2 net-next] net: ethernet: enetc: unlock XDP_REDIRECT
 for XDP non-linear buffers

> On Fri, Dec 09, 2022 at 01:19:44AM +0100, Lorenzo Bianconi wrote:
> > Even if full XDP_REDIRECT is not supported yet for non-linear XDP buffers
> > since we allow redirecting just into CPUMAPs, unlock XDP_REDIRECT for
> > S/G XDP buffer and rely on XDP stack to properly take care of the
> > frames.
> > 
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > Changes since v1:
> > - drop Fixes tag
> > - unlock XDP_REDIRECT
> > - populate missing XDP metadata
> > 
> > Please note this patch is just compile tested
> > ---
> 
> How would you like me to test this patch?

Hi Vladimir,

you can use xdp_redirect_cpu sample available in the kernel source tree.

> 
> >  drivers/net/ethernet/freescale/enetc/enetc.c | 27 +++++++++-----------
> >  1 file changed, 12 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> > index 8671591cb750..9fd15e1e692d 100644
> > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > @@ -1412,6 +1412,16 @@ static void enetc_add_rx_buff_to_xdp(struct enetc_bdr *rx_ring, int i,
> >  	/* To be used for XDP_TX */
> >  	rx_swbd->len = size;
> >  
> > +	if (!xdp_buff_has_frags(xdp_buff)) {
> > +		xdp_buff_set_frags_flag(xdp_buff);
> > +		shinfo->xdp_frags_size = size;
> > +	} else {
> > +		shinfo->xdp_frags_size += size;
> > +	}
> > +
> > +	if (page_is_pfmemalloc(rx_swbd->page))
> > +		xdp_buff_set_frag_pfmemalloc(xdp_buff);
> > +
> >  	skb_frag_off_set(frag, rx_swbd->page_offset);
> >  	skb_frag_size_set(frag, size);
> >  	__skb_frag_set_page(frag, rx_swbd->page);
> > @@ -1601,22 +1611,7 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring,
> >  			}
> >  			break;
> >  		case XDP_REDIRECT:
> > -			/* xdp_return_frame does not support S/G in the sense
> > -			 * that it leaks the fragments (__xdp_return should not
> > -			 * call page_frag_free only for the initial buffer).
> > -			 * Until XDP_REDIRECT gains support for S/G let's keep
> > -			 * the code structure in place, but dead. We drop the
> > -			 * S/G frames ourselves to avoid memory leaks which
> > -			 * would otherwise leave the kernel OOM.
> > -			 */
> > -			if (unlikely(cleaned_cnt - orig_cleaned_cnt != 1)) {
> > -				enetc_xdp_drop(rx_ring, orig_i, i);
> > -				rx_ring->stats.xdp_redirect_sg++;
> > -				break;
> > -			}
> > -
> >  			tmp_orig_i = orig_i;
> > -
> >  			while (orig_i != i) {
> >  				enetc_flip_rx_buff(rx_ring,
> >  						   &rx_ring->rx_swbd[orig_i]);
> > @@ -1628,6 +1623,8 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring,
> >  				enetc_xdp_free(rx_ring, tmp_orig_i, i);
> >  			} else {
> >  				xdp_redirect_frm_cnt++;
> > +				if (xdp_buff_has_frags(&xdp_buff))
> > +					rx_ring->stats.xdp_redirect_sg++;
> 
> Ideally we'd remove this counter altogether. Nothing interesting to see.

ok, I will get rid of it in the next version.

Regards,
Lorenzo

> 
> >  				rx_ring->stats.xdp_redirect++;
> >  			}
> >  		}
> > -- 
> > 2.38.1
> >

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