Re: [PATCH net v2] ixgbe: fix double clean of tx descriptors with xdp

On Thu, Aug 22, 2019 at 5:30 AM Ilya Maximets [off-list ref] 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 comletion queue ring.

s/comletion/completion/

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 don't need most of the
complications implemented in the regular 'ixgbe_clean_tx_irq()'
and 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 <redacted>
---

Tested-by: William Tu <redacted>

Instead of measuring tx performance at the tx machine, I measured the TX
performance at the other side (the traffic generating machine).  This time it
is more consistent and showing not much difference with (5.9Mpps) and
without this patch (6.1Mpps).

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 | 34 ++++++++------------
 1 file changed, 13 insertions(+), 21 deletions(-)

<snip>