Dear Björn,
On 01/21/19 17:33, bjorn.to...@gmail.com wrote: > From: Björn Töpel <bjorn.to...@intel.com> > > GCC will generate jump tables for switch-statements with more than 5 > case statements. An entry into the jump table is an indirect call, > which means that for CONFIG_RETPOLINE builds, this is rather > expensive. > > This commit replaces the switch-statement that acts on the XDP program > result with an if-clause. Maybe mention the performance improvement already here. I’d also put it into the commit message summary. Something like: > i40e: Speed up retpoline case by using if-clause If that jump tables are a common problem, I wonder, why the compiler cannot be adapted to generate better performing code or an option passed to the compiler. > The if-clause was also refactored into a common function that can be > used by AF_XDP zero-copy and non-zero-copy code. > > Performance prior this patch: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 18983018 0 > XDP-RX CPU total 18983018 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 18983012 0 > rx_queue_index 20:sum 18983012 > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0@enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 14,641,496 144,751,092 > tx 0 0 > > And after: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 24000986 0 > XDP-RX CPU total 24000986 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 24000985 0 > rx_queue_index 20:sum 24000985 > > +26% > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0@enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 17,623,578 163,503,263 > tx 0 0 > > +20% > > Signed-off-by: Björn Töpel <bjorn.to...@intel.com> > --- > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 31 ++++--------------- > .../ethernet/intel/i40e/i40e_txrx_common.h | 27 ++++++++++++++++ > drivers/net/ethernet/intel/i40e/i40e_xsk.c | 24 ++------------ > 3 files changed, 35 insertions(+), 47 deletions(-) […] Kind regards, Paul
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