This is an amended excerpt from Scott Wlaschin: https://gist.github.com/swlaschin/348b6b9e64d4b150cf86#file-typesafe-performance-with-compiler-directives-5-fsx-L224

Time.fsx

let time countN label f =
  let stopwatch = System.Diagnostics.Stopwatch()

  System.GC.Collect()
  printfn "Started"

  let getGcStats() =
    let gen0 = System.GC.CollectionCount(0)
    let gen1 = System.GC.CollectionCount(1)
    let gen2 = System.GC.CollectionCount(2)
    let mem = System.GC.GetTotalMemory(false)
    gen0, gen1, gen2, mem

  printfn "========================"
  printfn "%s" label
  printfn "========================"

  for iteration in [1..countN] do
    let gen0, gen1, gen2, mem = getGcStats()
    stopwatch.Restart()
    f()
    stopwatch.Stop()
    let gen0', gen1', gen2', mem' = getGcStats()

    let changeInMem = (mem'-mem)/1000L
    printfn "#%2i elapsed:%6ims gen0:%3i gen1:%3i gen2:%3i mem:%6iK" iteration stopwatch.ElapsedMilliseconds (gen0'-gen0) (gen1'-gen1) (gen2'-gen2) changeInMem