This sample program show how to use cpumap and the associated
tracepoints.
It provides command line stats, which shows how the XDP-RX process,
cpumap-enqueue and cpumap kthread dequeue is cooperating on a per CPU
basis. It also utilize the xdp_exception and xdp_redirect_err
transpoints to allow users quickly to identify setup issues.
One issue with ixgbe driver is that the driver reset the link when
loading XDP. This reset the procfs smp_affinity settings. Thus,
after loading the program, these must be reconfigured. The easiest
workaround it to reduce the RX-queue to e.g. two via:
# ethtool --set-channels ixgbe1 combined 2
And then add CPUs above 0 and 1, like:
# xdp_redirect_cpu --dev ixgbe1 --prog 2 --cpu 2 --cpu 3 --cpu 4
Another issue with ixgbe is that the page recycle mechanism is tied to
the RX-ring size. And the default setting of 512 elements is too
small. This is the same issue with regular devmap XDP_REDIRECT.
To overcome this I've been using 1024 rx-ring size:
# ethtool -G ixgbe1 rx 1024 tx 1024
V3:
- whitespace cleanups
- bpf tracepoint cannot access top part of struct
V4:
- report on kthread sched events, according to tracepoint change
- report average bulk enqueue size
V5:
- bpf_map_lookup_elem on cpumap not allowed from bpf_prog
use separate map to mark CPUs not available
V6:
- correct kthread sched summary output
V7:
- Added a --stress-mode for concurrently changing underlying cpumap
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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