On 2021/1/9 上午10:49, Charlie Somerville wrote:
This patch series introduces a new flag XDP_FLAGS_NO_TX which prevents the allocation of additional send queues for XDP programs.
This part I don't understand. Is such flag a must? I think the answer is probably not.
Why not simply do: 1) if we had sufficient TX queues, use dedicated TX queues for XDP_TX 2) if we don't, simple synchronize through spin_lock[1] Thanks [1] https://www.spinics.net/lists/bpf/msg32587.html
Included in this patch series is an implementation of XDP_FLAGS_NO_TX for the virtio_net driver. This flag is intended to be advisory - not all drivers must implement support for it. Many virtualised environments only provide enough virtio_net send queues for the number of processors allocated to the VM: # nproc 8 # ethtool --show-channels ens3 Channel parameters for ens3: Pre-set maximums: RX: 0 TX: 0 Other: 0 Combined: 8 In this configuration XDP is unusable because the virtio_net driver always tries to allocate an extra send queue for each processor - even if the XDP the program never uses the XDP_TX functionality. While XDP_TX is still unavailable in these environments, this new flag expands the set of XDP programs that can be used. This is my first contribution to the kernel, so apologies if I've sent this to the wrong list. I have tried to cc relevant maintainers but it's possible I may have missed some people. I'm looking forward to receiving feedback on this change. Charlie Somerville (2): xdp: Add XDP_FLAGS_NO_TX flag virtio_net: Implement XDP_FLAGS_NO_TX support drivers/net/virtio_net.c | 17 +++++++++++++---- include/uapi/linux/if_link.h | 5 ++++- 2 files changed, 17 insertions(+), 5 deletions(-)
