support measuring peak memory usage on mac

[rszymanski]

First of all, thank you for making this package!

I have noticed that measuring peak memory usage on macOS is not yet supported. I think I figured out a way how to achieve that.

Let me know if there is anything else I should include in the Pull Request!

Change Description

Adds support for measuring peak memory usage on macOS using the MACH API.

The solution was inspired by this Stack Overflow thread.

How I checked if it is measuring peak memory usage correctly

I compared it with the output of /usr/bin/time which also measures peak memory usage.

Here is the R script I used for testing:

# test_memuse.R

simulate_large_mem_call <- function(n = 1e7) {
  df <- data.frame(x = runif(n), y = runif(n))
  return(list(mean(c(df$x, df$y))))
}

result <- simulate_large_mem_call()

measured_memory_usage <- memuse::Sys.procmem()

# convert to numeric to compare with /usr/bin/time output
peak_memory_usage <- as.numeric(measured_memory_usage$peak)

print(measured_memory_usage)

print(paste0("Peak memory usage: ", peak_memory_usage))

And here is the output of /usr/bin/time -l Rscript test_memuse.R

Size:  223.234 MiB 
Peak:  375.828 MiB 
[1] "Peak memory usage: 394084352"
        0.42 real         0.34 user         0.05 sys
           394084352  maximum resident set size
                   0  average shared memory size
                   0  average unshared data size
                   0  average unshared stack size
               26015  page reclaims
                   0  page faults
                   0  swaps
                   0  block input operations
                   0  block output operations
                   0  messages sent
                   0  messages received
                   1  signals received
                  10  voluntary context switches
                  54  involuntary context switches
          4237421686  instructions retired
          1144689724  cycles elapsed
           379619392  peak memory footprint

The maximum resident set size reported by /usr/bin/time matches the peak memory usage reported by memuse.