Constant PPROF_BACKEND_ENV 

pub const PPROF_BACKEND_ENV: &str = "PPROF_ALLOC_BACKEND";

Environment variable that selects the pprof backend when native jemalloc profiling support is compiled in.

Set this before process startup. Supported wrapper values are wrapper, pprof-alloc, and rust; any other value, including an unset variable, selects native jemalloc profiling when the allocator-jemalloc feature is enabled and the active allocator is jemalloc.