> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of Maciej > Fijalkowski > Sent: Thursday, August 19, 2021 5:30 PM > To: intel-wired-lan@xxxxxxxxxxxxxxxx > Cc: joamaki@xxxxxxxxx; Lobakin, Alexandr <alexandr.lobakin@xxxxxxxxx>; > netdev@xxxxxxxxxxxxxxx; toke@xxxxxxxxxx; bjorn@xxxxxxxxxx; kuba@xxxxxxxxxx; > bpf@xxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; Karlsson, Magnus > <magnus.karlsson@xxxxxxxxx> > Subject: [Intel-wired-lan] [PATCH v7 intel-next 8/9] ice: introduce XDP_TX fallback > path > > Under rare circumstances there might be a situation where a requirement of having > XDP Tx queue per CPU could not be fulfilled and some of the Tx resources have > to be shared between CPUs. This yields a need for placing accesses to xdp_ring > inside a critical section protected by spinlock. > These accesses happen to be in the hot path, so let's introduce the static branch > that will be triggered from the control plane when driver could not provide Tx queue > dedicated for XDP on each CPU. > > Currently, the design that has been picked is to allow any number of XDP Tx > queues that is at least half of a count of CPUs that platform has. > For lower number driver will bail out with a response to user that there were not > enough Tx resources that would allow configuring XDP. The sharing of rings is > signalled via static branch enablement which in turn indicates that lock for xdp_ring > accesses needs to be taken in hot path. > > Approach based on static branch has no impact on performance of a non-fallback > path. One thing that is needed to be mentioned is a fact that the static branch will > act as a global driver switch, meaning that if one PF got out of Tx resources, then > other PFs that ice driver is servicing will suffer. However, given the fact that HW > that ice driver is handling has 1024 Tx queues per each PF, this is currently an > unlikely scenario. > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx> > --- > drivers/net/ethernet/intel/ice/ice.h | 3 ++ > drivers/net/ethernet/intel/ice/ice_lib.c | 4 +- > drivers/net/ethernet/intel/ice/ice_main.c | 53 ++++++++++++++++--- > drivers/net/ethernet/intel/ice/ice_txrx.c | 16 +++++- > drivers/net/ethernet/intel/ice/ice_txrx.h | 1 + > drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 7 ++- > 6 files changed, 75 insertions(+), 9 deletions(-) > Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@xxxxxxxxx>
