When sending moderate amounts of ReconnectingPTY traffic to coderd, we observe high memory usage that eventually is released once the load drops.

This is the result of sending approximately 4MiB/s of ReconnectingPTY traffic to coderd (4096 kB @ 10Hz).

We see memory usage rise up to approx 5GiB and then drop off after the traffic subsides.

A pprof sample taken at 15:36 (indicated by the blue line) shows a high proportion of memory usage by device.PopulatePools:

github.com/tailscale/wireguard-go/device.(*WaitPool).Get
/home/runner/go/pkg/mod/github.com/tailscale/wireguard-go@v0.0.0-20221219190806-4fa124729667/device/pools.go

  Total:           0     3.92GB (flat, cum) 97.76%
     36            .     3.92GB           ??? 

Pprof available here:

cian-jun12-heap.pprof.gz
cian-jun12-goroutine.pprof.gz