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

[William Tu]

On Thu, Aug 22, 2019 at 11:10 PM BjÃrn TÃpel <bjorn.topel@xxxxxxxxx> wrote:
>
> 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?
>

No noticeable performance degradation seen this time.
Thanks,
William