FxHashMap made me faster, memmap makes me slower, guess I'm using it wrong

src/main/rust/Cargo.toml

@@ -9,7 +9,7 @@ edition = "2021"
 bstr = "1.9.1"
 fast-float = "0.2.0"
 memchr = "2.7.4"
-memmap = "0.7.0"
+memmap2 = "0.9.4"
 polars = { version = "0.36.2", features = ["csv", "lazy", "nightly", "streaming"]}
 rayon = "1.10.0"
 rustc-hash = "2.0.0"
@@ -47,6 +47,7 @@ name = "phcs"
 harness = false
 
 [profile.release]
+debug = true
 lto = "fat"
-strip = "symbols"
+#strip = "symbols"
 panic = "abort"