Introduce a "jemalloc-shim" crate

Cargo.toml

@@ -159,6 +159,7 @@ members = [
 	"polkadot/core-primitives",
 	"polkadot/erasure-coding",
 	"polkadot/erasure-coding/fuzzer",
+	"polkadot/jemalloc-shim",
 	"polkadot/node/collation-generation",
 	"polkadot/node/core/approval-voting",
 	"polkadot/node/core/approval-voting-parallel",
@@ -1115,6 +1116,7 @@ polkadot-core-primitives = { path = "polkadot/core-primitives", default-features
 polkadot-dispute-distribution = { path = "polkadot/node/network/dispute-distribution", default-features = false }
 polkadot-erasure-coding = { path = "polkadot/erasure-coding", default-features = false }
 polkadot-gossip-support = { path = "polkadot/node/network/gossip-support", default-features = false }
+polkadot-jemalloc-shim = { path = "polkadot/jemalloc-shim" }
 polkadot-network-bridge = { path = "polkadot/node/network/bridge", default-features = false }
 polkadot-node-collation-generation = { path = "polkadot/node/collation-generation", default-features = false }
 polkadot-node-core-approval-voting = { path = "polkadot/node/core/approval-voting", default-features = false }

polkadot/Cargo.toml

@@ -67,7 +67,7 @@ path = "src/bin/prepare-worker.rs"
 
 [dependencies]
 color-eyre = { workspace = true }
-tikv-jemallocator = { optional = true, features = ["unprefixed_malloc_on_supported_platforms"], workspace = true }
+polkadot-jemalloc-shim = { workspace = true }
 
 # Crates in our workspace, defined as dependencies so we can pass them feature flags.
 polkadot-cli = { features = ["rococo-native", "westend-native"], workspace = true, default-features = true }
@@ -80,7 +80,7 @@ polkadot-node-core-pvf-common = { workspace = true, default-features = true }
 polkadot-node-core-pvf-execute-worker = { workspace = true, default-features = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
-tikv-jemallocator = { workspace = true, features = ["unprefixed_malloc_on_supported_platforms"] }
+polkadot-jemalloc-shim = { workspace = true, features = ["jemalloc-allocator"] }
 
 [dev-dependencies]
 assert_cmd = { workspace = true }
@@ -99,13 +99,7 @@ try-runtime = ["polkadot-cli/try-runtime"]
 fast-runtime = ["polkadot-cli/fast-runtime"]
 runtime-metrics = ["polkadot-cli/runtime-metrics"]
 pyroscope = ["polkadot-cli/pyroscope"]
-jemalloc-allocator = [
-	"dep:tikv-jemallocator",
-	"polkadot-cli/jemalloc-allocator",
-	"polkadot-node-core-pvf-prepare-worker/jemalloc-allocator",
-	"polkadot-node-core-pvf/jemalloc-allocator",
-	"polkadot-overseer/jemalloc-allocator",
-]
+jemalloc-allocator = ["polkadot-jemalloc-shim/jemalloc-allocator"]
 
 # Generate the metadata hash needed for CheckMetadataHash
 # in the builtin test runtimes (westend and rococo).

polkadot/jemalloc-shim/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "polkadot-jemalloc-shim"
+version = "1.0.0"
+description = "Shim crate to enable jemalloc-allocator feature for polkadot crates"
+license.workspace = true
+authors.workspace = true
+edition.workspace = true
+homepage.workspace = true
+repository.workspace = true
+
+[lints]
+workspace = true
+
+[dependencies]
+polkadot-cli = { optional = true, workspace = true }
+polkadot-node-core-pvf = { optional = true, workspace = true }
+polkadot-node-core-pvf-prepare-worker = { optional = true, workspace = true }
+polkadot-overseer = { optional = true, workspace = true }
+tikv-jemallocator = { optional = true, features = ["unprefixed_malloc_on_supported_platforms"], workspace = true }
+
+[features]
+jemalloc-allocator = [
+	"dep:tikv-jemallocator",
+	"polkadot-cli/jemalloc-allocator",
+	"polkadot-node-core-pvf-prepare-worker/jemalloc-allocator",
+	"polkadot-node-core-pvf/jemalloc-allocator",
+	"polkadot-overseer/jemalloc-allocator",
+]

polkadot/jemalloc-shim/src/lib.rs

@@ -0,0 +1,26 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Shim crate to enable `jemalloc-allocator` feature for Polkadot crates.
+//!
+//! Because [there doesn't exist any easier way right now](https://github.com/rust-lang/cargo/issues/1197), we
+//! need an entire crate to handle `jemalloc` enabling/disabling. This way we can enable it by
+//! default on Linux, but have it optional on all other OSes.
+
+/// Sets the global allocator to `jemalloc` when the feature is enabled.
+#[cfg(feature = "jemalloc-allocator")]
+#[global_allocator]
+static ALLOC: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;

polkadot/src/main.rs

@@ -20,12 +20,6 @@
 
 use color_eyre::eyre;
 
-/// Global allocator. Changing it to another allocator will require changing
-/// `memory_stats::MemoryAllocationTracker`.
-#[cfg(any(target_os = "linux", feature = "jemalloc-allocator"))]
-#[global_allocator]
-static ALLOC: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
-
 fn main() -> eyre::Result<()> {
 	color_eyre::install()?;
 	polkadot_cli::run()?;

prdoc/pr_10709.prdoc

@@ -0,0 +1,10 @@
+title: Introduce a "jemalloc-shim" crate
+doc:
+- audience: Node Operator
+  description: |-
+    This crate basically serves as a hack to properly enable `jemalloc` on Linux and disable it on all other OSes by default.
+crates:
+- name: polkadot
+  bump: patch
+- name: polkadot-jemalloc-shim
+  bump: patch