>
> Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx> writes:
>
> > >
> > > Lorenzo Bianconi <lorenzo@xxxxxxxxxx> writes:
> > >
> > > > ...
> > > > diff --git a/drivers/net/ethernet/marvell/mvneta.c
> > > > b/drivers/net/ethernet/marvell/mvneta.c
> > > > index 9d460a270601..0c7b84ca6efc 100644
> > > > --- a/drivers/net/ethernet/marvell/mvneta.c
> > > > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > > > ...
> > > > @@ -2320,8 +2325,12 @@ mvneta_swbm_build_skb(struct > mvneta_port
> > > *pp,
> > > > struct page_pool *pool,
> > > > struct xdp_buff *xdp, u32 desc_status)
> > > > {
> > > > struct skb_shared_info *sinfo = >
> > > xdp_get_shared_info_from_buff(xdp);
> > > > - int i, num_frags = sinfo->nr_frags;
> > > > struct sk_buff *skb;
> > > > + u8 num_frags;
> > > > + int i;
> > > > +
> > > > + if (unlikely(xdp_buff_is_mb(xdp)))
> > > > + num_frags = sinfo->nr_frags;
> > >
> > > Hi,
> > > nit, it seems that the num_frags assignment can be moved after the
> > > other
> > > 'if' condition you added (right before the 'for' for num_frags), or
> > > even be
> > > eliminated completely so that sinfo->nr_frags is used directly.
> > > Either way it looks like you can remove one 'if'.
> > >
> > > Shay
> >
> > Hi Shay,
> >
> > we can't move nr_frags assignement after build_skb() since this field
> > will be
> > overwritten by that call.
> >
> > Regards,
> > Lorenzo
> >
>
> Sorry, silly mistake of me.
>
> Guess this assignment can be done anyway since there doesn't seem to be new
> cache misses introduced by it.
> Anyway, nice catch, sorry for misleading you
actually we probably have a cache miss in this case for the single-buffer use case
since skb_shared_info will not be in the same cache-line.
Regards,
Lorenzo
>
> > >
> > > > skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
> > > > if (!skb)
> > > > @@ -2333,6 +2342,9 @@ mvneta_swbm_build_skb(struct > mvneta_port
> > > *pp,
> > > > struct page_pool *pool,
> > > > skb_put(skb, xdp->data_end - xdp->data);
> > > > skb->ip_summed = mvneta_rx_csum(pp, desc_status);
> > > > + if (likely(!xdp_buff_is_mb(xdp)))
> > > > + goto out;
> > > > +
> > > > for (i = 0; i < num_frags; i++) {
> > > > skb_frag_t *frag = &sinfo->frags[i];
> > > > @@ -2341,6 +2353,7 @@ mvneta_swbm_build_skb(struct >
> > > mvneta_port *pp,
> > > > struct page_pool *pool,
> > > > skb_frag_size(frag), PAGE_SIZE);
> > > > }
> > > > +out:
> > > > return skb;
> > > > }
> > >
>
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