Struggling to use future with profvis

@HenrikBengtsson try to run the following

```r
library(future)
library(furrr)

# 50,000 instances of `mtcars`
xs <- rep(list(mtcars), 50000)

# Two workers
plan(multisession, workers = 2)

profvis::profvis({
future_map(xs, identity)
})
```

or

```r
library(future)
library(future.apply)

# 50,000 instances of `mtcars`
xs <- rep(list(mtcars), 50000)

# Two workers
plan(multisession, workers = 2)

profvis::profvis({
future_lapply(xs, identity)
})
```

For me, both of these return something like

> profvis: code exited with error: Caught an unexpected error of class FutureError when trying to launch future () on backend of class MultisessionFutureBackend. The reason was: MultisessionFuture () failed to launch future on cluster RichSOCKnode futureverse/furrr#1 (PID 58154 on localhost ‘localhost’). The reason reported was ‘error writing to connection’. Post-mortem diagnostic: A process with this PID exists, which suggests that the localhost worker is still alive. The total size of the 5 globals exported is 89.19 MiB The three largest globals are ‘...furrr_chunk_args’ (89.19 MiB of class ‘list’), ‘...furrr_fn’ (185 bytes of class ‘function’) and ‘...furrr_dots’ (31 bytes of class ‘list’) [future (20fb4acd5a0a2950ebd05810b60d69d9-1); on 20fb4acd5a0a2950ebd05810b60d69d9@davisvaughan-01HQ<58109>]

Any ideas?