diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 000000000000..1f678a632560
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,3 @@
+[env]
+# Tune jemalloc (https://github.com/pola-rs/polars/issues/18088).
+JEMALLOC_SYS_WITH_MALLOC_CONF = "dirty_decay_ms:500,muzzy_decay_ms:-1"
diff --git a/.gitignore b/.gitignore
index 4e34b437a91f..3c03000ed764 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,7 +29,6 @@ __pycache__/
 .coverage
 
 # Rust
-.cargo/
 target/
 
 # Data
diff --git a/py-polars/Cargo.toml b/py-polars/Cargo.toml
index 7998cf714b81..e911d5c53e77 100644
--- a/py-polars/Cargo.toml
+++ b/py-polars/Cargo.toml
@@ -113,7 +113,11 @@ built = { version = "0.7", features = ["chrono", "git2", "cargo-lock"], optional
 [target.'cfg(all(any(not(target_family = "unix"), allocator = "mimalloc"), not(allocator = "default")))'.dependencies]
 mimalloc = { version = "0.1", default-features = false }
 
-[target.'cfg(all(target_family = "unix", not(allocator = "mimalloc"), not(allocator = "default")))'.dependencies]
+# Feature background_threads is unsupported on MacOS (https://github.com/jemalloc/jemalloc/issues/843).
+[target.'cfg(all(target_family = "unix", not(target_os = "macos"), not(allocator = "mimalloc"), not(allocator = "default")))'.dependencies]
+jemallocator = { version = "0.5", features = ["disable_initial_exec_tls", "background_threads"] }
+
+[target.'cfg(all(target_family = "unix", target_os = "macos", not(allocator = "mimalloc"), not(allocator = "default")))'.dependencies]
 jemallocator = { version = "0.5", features = ["disable_initial_exec_tls"] }
 
 [features]