alloc: add force-jemalloc-macos feature

src/alloc/Cargo.toml

@@ -12,21 +12,7 @@ workspace = true
 [dependencies]
 mz-ore = { path = "../ore", default-features = false }
 workspace-hack = { version = "0.0.0", path = "../workspace-hack", optional = true }
-
-# Disable jemalloc on macOS, as it is not well supported [0][1][2]. The issues
-# present as runaway latency on load test workloads that are comfortably handled
-# by the macOS system allocator. Consider re-evaluating if jemalloc's macOS
-# support improves.
-#
-# [0]: https://github.com/jemalloc/jemalloc/issues/26
-# [1]: https://github.com/jemalloc/jemalloc/issues/843
-# [2]: https://github.com/jemalloc/jemalloc/issues/1467
-#
-# Furthermore, as of August 2022, some engineers are using profiling tools, e.g.
-# `heaptrack`, that only work with the system allocator.
-[target.'cfg(not(target_os = "macos"))'.dependencies]
 mz-prof = { path = "../prof", default-features = false }
-mz-prof-http = { path = "../prof-http", default-features = false }
 # According to jemalloc developers, `background_threads` should always be
 # enabled, except in "esoteric" situations that don't apply to Materialize
 # (namely, if the application relies on new threads not being created for
@@ -35,10 +21,32 @@ mz-prof-http = { path = "../prof-http", default-features = false }
 # See: https://github.com/jemalloc/jemalloc/issues/956#issuecomment-316224733
 tikv-jemallocator = { version = "0.5.0", features = ["profiling", "stats", "unprefixed_malloc_on_supported_platforms", "background_threads"], optional = true }
 
+[target.'cfg(not(target_os = "macos"))'.dependencies]
+mz-prof-http = { path = "../prof-http", default-features = false }
+
 [features]
 default = ["workspace-hack"]
 # Whether to enable the use of jemalloc on platforms that support it.
 jemalloc = ["tikv-jemallocator", "mz-prof/jemalloc", "mz-prof-http/jemalloc"]
+# By default disable jemalloc on macOS, as it is not well supported [0][1]. The issues
+# present as runaway latency on load test workloads that are comfortably handled
+# by the macOS system allocator. Consider re-evaluating if jemalloc's macOS
+# support improves.
+#
+# [0]: https://github.com/jemalloc/jemalloc/issues/26
+# [1]: https://github.com/jemalloc/jemalloc/issues/843
+#
+# Furthermore, as of August 2022, some engineers are using profiling tools, e.g.
+# `heaptrack`, that only work with the system allocator.
+#
+# Note that profiling as provided by `mz-prof-http` is not enabled for macos, as it
+# appears to not work at all.
+#
+# Unfortunately, there doesn't appear to be a way to tell cargo to only include the
+# tikv-jemallocator dependency if `force-jemalloc-macos` is enabled AND the platform
+# is macos (Cargo doesn't support all(feature, platform) in the `target.cfg()` fields. This
+# means mac users have to build one more dep :(.
+force-jemalloc-macos = []
 
 [package.metadata.cargo-udeps.ignore]
 # The only reason we depend on mz-prof-http

src/alloc/src/lib.rs

@@ -9,15 +9,23 @@
 
 use mz_ore::metrics::MetricsRegistry;
 
-#[cfg(all(not(target_os = "macos"), feature = "jemalloc", not(miri)))]
+#[cfg(all(
+    any(feature = "force-jemalloc-macos", not(target_os = "macos")),
+    feature = "jemalloc",
+    not(miri)
+))]
 #[global_allocator]
 static ALLOC: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
 
 /// Registers metrics for the global allocator into the provided registry.
 ///
 /// What metrics are registered varies by platform. Not all platforms use
 /// allocators that support metrics.
-#[cfg(any(target_os = "macos", not(feature = "jemalloc"), miri))]
+#[cfg(any(
+    all(not(feature = "force-jemalloc-macos"), target_os = "macos"),
+    not(feature = "jemalloc"),
+    miri
+))]
 #[allow(clippy::unused_async)]
 pub async fn register_metrics_into(_: &MetricsRegistry) {
     // No-op on platforms that don't use jemalloc.
@@ -27,7 +35,11 @@ pub async fn register_metrics_into(_: &MetricsRegistry) {
 ///
 /// What metrics are registered varies by platform. Not all platforms use
 /// allocators that support metrics.
-#[cfg(all(not(target_os = "macos"), feature = "jemalloc", not(miri)))]
+#[cfg(all(
+    any(feature = "force-jemalloc-macos", not(target_os = "macos")),
+    feature = "jemalloc",
+    not(miri)
+))]
 pub async fn register_metrics_into(registry: &MetricsRegistry) {
     mz_prof::jemalloc::JemallocMetrics::register_into(registry).await;
 }

src/clusterd/Cargo.toml

@@ -44,6 +44,7 @@ workspace-hack = { version = "0.0.0", path = "../workspace-hack" }
 [features]
 default = ["tokio-console", "jemalloc"]
 jemalloc = ["mz-alloc/jemalloc"]
+force-jemalloc-macos = ["mz-alloc/force-jemalloc-macos"]
 tokio-console = ["mz-ore/tokio-console"]
 
 [package.metadata.cargo-udeps.ignore]

src/environmentd/Cargo.toml

@@ -168,6 +168,7 @@ default = ["tokio-console", "jemalloc"]
 # access to the file system.
 dev-web = []
 jemalloc = ["mz-alloc/jemalloc"]
+force-jemalloc-macos = ["mz-alloc/force-jemalloc-macos"]
 test = [
     "postgres",
     "regex",