> > static __always_inline void
> > @@ -116,7 +120,8 @@ struct xdp_frame {
> > u16 len;
> > u16 headroom;
> > u32 metasize:8;
> > - u32 frame_sz:24;
> > + u32 frame_sz:23;
> > + u32 mb:1; /* xdp non-linear frame */
> > /* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time,
> > * while mem info is valid on remote CPU.
> > */
>
> So, it seems that these bitfield's are the root-cause of the
> performance regression. Credit to Alexei whom wisely already point
> this out[1] in V2 ;-)
>
> [1] https://lore.kernel.org/netdev/20200904010705.jm6dnuyj3oq4cpjd@xxxxxxxxxxxxxxxxxxxxxxxxxxxx/
yes, shame on me..yesterday I recalled email from Alexei debugging the issue
reported by Magnus.
In the current approach I am testing (not posted upstream yet) I reduced the
size of xdp_mem_info as proposed by Jesper in [0] and I added a flags field
in xdp_frame/xdp_buff we can use for multiple features (e.g. multi-buff or hw csum
hints). Doing so, running xdp_rxq_info sample on ixgbe 10Gbps NIC I do not have any
performance regressions for xdp_tx or xdp_drop. Same results have been reported by
Magnus off-list on i40e (we have a 1% regression on xdp_sock tests iiuc).
I will continue working on this.
Regards,
Lorenzo
[0] https://patchwork.kernel.org/project/netdevbpf/patch/20210409223801.104657-2-mcroce@xxxxxxxxxxxxxxxxxxx/
>
>
> > @@ -179,6 +184,7 @@ void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
> > xdp->data_end = frame->data + frame->len;
> > xdp->data_meta = frame->data - frame->metasize;
> > xdp->frame_sz = frame->frame_sz;
> > + xdp->mb = frame->mb;
> > }
> >
> > static inline
> > @@ -205,6 +211,7 @@ int xdp_update_frame_from_buff(struct xdp_buff *xdp,
> > xdp_frame->headroom = headroom - sizeof(*xdp_frame);
> > xdp_frame->metasize = metasize;
> > xdp_frame->frame_sz = xdp->frame_sz;
> > + xdp_frame->mb = xdp->mb;
> >
> > return 0;
> > }
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
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