.NET Async operation performance problems (no replies)

If I have a code that ExecuteNonQuery or ExecuteReader or ExecuteScalar they work just ok and the performance is... well, quite ok. Now, if I wan't to not eat up not so much resources, I run the async versions, ExecuteNonQueryAsync or ExecuteReaderAsync or ExecuteScalarAsync and I expect the business logic thread to be non-blocked while SQL is executing. For technical background details see: http://fsprojects.github.io/SQLProvider/core/async.html

Anyways, this is the expected result. Actual result is that if I run this with 10 of threads (like web servers usually do), not only the threads are not locked ( http://stackoverflow.com/questions/30551459/mysql-c-sharp-async-methods-doesnt-work ), but the whole server is jammed and I got SQL-deadlocks and everything.

Here is the sample source code in F#:

let cstr = "server = localhost; database = TestDB; uid = root;pwd = 12345"

let ExecuteSqlOld (query : string) parameters =
    use rawSqlConnection = new MySqlConnection(cstr)
    rawSqlConnection.Open() 
    use command = new MySqlCommand(query, rawSqlConnection)
    parameters |> List.iter(fun (par:string*string) -> command.Parameters.AddWithValue(par) |> ignore)
    let affectedRows = command.ExecuteNonQuery()
    ()

let ExecuteSql (query : string) parameters =
  async {
    use rawSqlConnection = new MySqlConnection(cstr)
    do! rawSqlConnection.OpenAsync() |> Async.AwaitTask
    use command = new MySqlCommand(query, rawSqlConnection)
    parameters |> List.iter(fun (par:string*string) -> command.Parameters.AddWithValue(par) |> ignore)
    let! affectedRows = command.ExecuteNonQueryAsync() |> Async.AwaitTask
    ()
  }

The problem is also reproducable with the source code in this repo, under Thread test, changing the last method to use SubmitUpdatesAsync:
https://github.com/fsprojects/SQLProvider/blob/master/tests/SqlProvider.Tests/scripts/MySqlTests.fsx