ARROW-6910. When loading the R package after that patch merged, I get this new message:
https://github.com/jemalloc/jemalloc/blob/3d84bd57f4954a17059bd31330ec87d3c1876411/src/background_thread.c#L884-L887 is where the message comes from. Tracing that further, have_background_thread comes from https://github.com/jemalloc/jemalloc/blob/21cfe59ff7b10a61dabe26cd3dbfb7a255e1f5e8/include/jemalloc/internal/jemalloc_preamble.h.in#L205-L211, which gets set in configure.ac here: https://github.com/jemalloc/jemalloc/blob/d2dddfb82aac9f2212922eb90324e84790704bfe/configure.ac#L2155-L2157
In sum, on my system, that flag doesn't get set, so have_background_thread is false, and when that is false and the background_thread option is true, I get that message printed. And I do not want to see that message.
cc Wes McKinney