From 5151db602fb4495daa09d0e42668a0b724509ab8 Mon Sep 17 00:00:00 2001
From: "Brian G. Milnes" <briangmilnes@gmail.com>
Date: Wed, 18 Mar 2026 18:17:38 -0700
Subject: [PATCH] Use jemalloc as global allocator on unix

On Linux, switching from glibc malloc to jemalloc saves avg 12%, peak 14%
RSS and avg 9%, peak 14% wall time across 6 open-source Verus projects,
with zero code changes. macOS is not yet benchmarked. jemalloc is not
available on Windows.

The `unprefixed_malloc_on_supported_platforms` feature is required so that
jemalloc replaces C-level malloc/free globally, not just Rust's allocator.
Without it, librustc_driver.so (which uses C malloc via LLVM) fights with
jemalloc over the heap, causing corruption during vstd build.

Benchmarks and analysis: https://github.com/briangmilnes/verus-heaptrack

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 source/Cargo.lock              | 21 +++++++++++++++++++++
 source/rust_verify/Cargo.toml  |  3 +++
 source/rust_verify/src/main.rs |  4 ++++
 3 files changed, 28 insertions(+)

diff --git a/source/Cargo.lock b/source/Cargo.lock
index ad08880d74..ffdec9d551 100644
--- a/source/Cargo.lock
+++ b/source/Cargo.lock
@@ -1902,6 +1902,7 @@ dependencies = [
  "serde_json",
  "sha2",
  "sise",
+ "tikv-jemallocator",
  "vir",
  "win32job",
 ]
@@ -2386,6 +2387,26 @@ dependencies = [
  "syn 2.0.101",
 ]
 
+[[package]]
+name = "tikv-jemalloc-sys"
+version = "0.6.1+5.3.0-1-ge13ca993e8ccb9ba9847cc330696e02839f328f7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd8aa5b2ab86a2cefa406d889139c162cbb230092f7d1d7cbc1716405d852a3b"
+dependencies = [
+ "cc",
+ "libc",
+]
+
+[[package]]
+name = "tikv-jemallocator"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0359b4327f954e0567e69fb191cf1436617748813819c94b8cd4a431422d053a"
+dependencies = [
+ "libc",
+ "tikv-jemalloc-sys",
+]
+
 [[package]]
 name = "time"
 version = "0.3.41"
diff --git a/source/rust_verify/Cargo.toml b/source/rust_verify/Cargo.toml
index eabc04a665..edfa98f7d6 100644
--- a/source/rust_verify/Cargo.toml
+++ b/source/rust_verify/Cargo.toml
@@ -24,6 +24,9 @@ console = { version = "0.15", default-features = false, features = ["ansi-parsin
 indexmap = { version = "1" }
 rustc_mir_build_verus = { path = "../rustc_mir_build", package = "rustc_mir_build" }
 
+[target.'cfg(unix)'.dependencies]
+tikv-jemallocator = { version = "0.6", features = ["unprefixed_malloc_on_supported_platforms"] }
+
 [target.'cfg(windows)'.dependencies]
 win32job = "1"
 
diff --git a/source/rust_verify/src/main.rs b/source/rust_verify/src/main.rs
index 7210bf4991..db25c0e70f 100644
--- a/source/rust_verify/src/main.rs
+++ b/source/rust_verify/src/main.rs
@@ -1,5 +1,9 @@
 #![feature(rustc_private)]
 
+#[cfg(target_family = "unix")]
+#[global_allocator]
+static GLOBAL: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
+
 use rust_verify::util::{VerusBuildProfile, verus_build_info};
 
 extern crate rustc_driver;