Re: [PATCH net v3] ixgbe: fix double clean of tx descriptors with xdp

[BjÃrn TÃpel]

On 2019-08-22 19:32, William Tu wrote:
> On Thu, Aug 22, 2019 at 10:21 AM Alexander Duyck
> <alexander.duyck@xxxxxxxxx> wrote:
> > On Thu, Aug 22, 2019 at 10:12 AM Ilya Maximets <i.maximets@xxxxxxxxxxx> wrote:
> > > Tx code doesn't clear the descriptors' status after cleaning.
> > > So, if the budget is larger than number of used elems in a ring, some
> > > descriptors will be accounted twice and xsk_umem_complete_tx will move
> > > prod_tail far beyond the prod_head breaking the completion queue ring.
> > >
> > > Fix that by limiting the number of descriptors to clean by the number
> > > of used descriptors in the tx ring.
> > >
> > > 'ixgbe_clean_xdp_tx_irq()' function refactored to look more like
> > > 'ixgbe_xsk_clean_tx_ring()' since we're allowed to directly use
> > > 'next_to_clean' and 'next_to_use' indexes.
> > >
> > > Fixes: 8221c5eba8c1 ("ixgbe: add AF_XDP zero-copy Tx support")
> > > Signed-off-by: Ilya Maximets <i.maximets@xxxxxxxxxxx>
> > > ---
> > >
> > > Version 3:
> > >    * Reverted some refactoring made for v2.
> > >    * Eliminated 'budget' for tx clean.
> > >    * prefetch returned.
> > >
> > > Version 2:
> > >    * 'ixgbe_clean_xdp_tx_irq()' refactored to look more like
> > >      'ixgbe_xsk_clean_tx_ring()'.
> > >
> > >   drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 29 ++++++++------------
> > >   1 file changed, 11 insertions(+), 18 deletions(-)
> >
> > Thanks for addressing my concerns.
> >
> > Acked-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
>
> Thanks.
>
> Tested-by: William Tu <u9012063@xxxxxxxxx>

Will, thanks for testing! For this patch, did you notice any performance
degradation?


Cheers,
BjÃrn