On Linux batching.Conn will now write a vector of
coalesced buffers via sendmmsg(2) instead of copying
fragments into a single buffer.
Scatter-gather I/O has been available on Linux since the
earliest days (reworked in 2.6.24). Kernel passes fragments
to the driver if it supports it, otherwise linearizes
upon receiving the data.
Removing the copy overhead from userspace yields up to 4-5%
packet and bitrate improvement on Linux with GSO enabled:
46Gb/s 4.4m pps vs 44Gb/s 4.2m pps w/32 Peer Relay client flows.
Updates tailscale/corp#36989
Change-Id: Idb2248d0964fb011f1c8f957ca555eab6a6a6964
Signed-off-by: Alex Valiushko <alexvaliushko@tailscale.com>
330a17b7d7