From 361c48f6560b36bc665324b4618ccb089f073ac2 Mon Sep 17 00:00:00 2001
From: Rayhaan Jaufeerally <rayhaan+github@rayhaan.ch>
Date: Sun, 4 Oct 2026 01:03:16 +0200
Subject: [PATCH] Use jemalloc as the daemon's memory allocator

A full table from several neighbors means millions of small, long-lived
allocations that are replaced as routes change. jemalloc keeps the
resident size of such a workload closer to what is in use than the
system allocator does, glibc's in particular, and does not depend on
the C library the binary is linked with. Not on MSVC, which jemalloc
does not support.

Building now needs a C compiler and make; the installation page says
so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 Cargo.lock                                    | 43 +++++++++++++++++++
 Cargo.toml                                    |  2 +
 bin/bgp/Cargo.toml                            |  5 +++
 bin/bgp/src/main.rs                           |  7 +++
 .../docs/getting-started/installation.md      |  3 ++
 5 files changed, 60 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 9f59f8b..cbf5746 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -164,6 +164,7 @@ dependencies = [
  "clap",
  "eyre",
  "protobuf",
+ "tikv-jemallocator",
  "tokio",
  "tracing",
  "tracing-subscriber",
@@ -373,6 +374,16 @@ version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d71b6127be86fdcfddb610f7182ac57211d4b18a3e9c82eb2d17662f2227ad6a"
 
+[[package]]
+name = "cc"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f74872d07caf508b30a21f6836e7d7016a2eaf7d9ff4f48deaa58cd8a0407630"
+dependencies = [
+ "find-msvc-tools",
+ "shlex",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -489,6 +500,12 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
 
+[[package]]
+name = "find-msvc-tools"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aedcfb3409746eddb02b9e19ebda1c3394f759a152e48ee875a0844d1b955484"
+
 [[package]]
 name = "flate2"
 version = "1.1.10"
@@ -1476,6 +1493,12 @@ dependencies = [
  "lazy_static",
 ]
 
+[[package]]
+name = "shlex"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.2"
@@ -1657,6 +1680,26 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "tikv-jemalloc-sys"
+version = "0.7.1+5.3.1-0-g81034ce1f1373e37dc865038e1bc8eeecf559ce8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a2825c78386b4ae0314074867860ba9577875de945f05992c38815cbec327f0"
+dependencies = [
+ "cc",
+ "libc",
+]
+
+[[package]]
+name = "tikv-jemallocator"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "249f09e49ab1609436f34c776e84231bead18d6a955f119f939bdc1d847561bd"
+dependencies = [
+ "libc",
+ "tikv-jemalloc-sys",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.8.4"
diff --git a/Cargo.toml b/Cargo.toml
index f234901..98438de 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -63,3 +63,5 @@ hashbrown = "0.17"
 axum = "0.8.9"
 tokio-stream = { version = "0.1.19", features = ["sync"] }
 reqwest = { version = "0.13.5", default-features = false, features = ["json"] }
+# The daemon's memory allocator; see bin/bgp/src/main.rs.
+tikv-jemallocator = "0.7.0"
diff --git a/bin/bgp/Cargo.toml b/bin/bgp/Cargo.toml
index 383a248..45e1820 100644
--- a/bin/bgp/Cargo.toml
+++ b/bin/bgp/Cargo.toml
@@ -18,5 +18,10 @@ tokio.workspace      = true
 tracing.workspace    = true
 tracing-subscriber.workspace = true
 
+# jemalloc does not build with the MSVC toolchain; there the system
+# allocator is used.
+[target.'cfg(not(target_env = "msvc"))'.dependencies]
+tikv-jemallocator.workspace = true
+
 [lints]
 workspace = true
diff --git a/bin/bgp/src/main.rs b/bin/bgp/src/main.rs
index 5c905b8..5f453c5 100644
--- a/bin/bgp/src/main.rs
+++ b/bin/bgp/src/main.rs
@@ -13,6 +13,13 @@ use crate::logging::LoggingArgs;
 
 mod logging;
 
+// jemalloc, rather than the C library's allocator. Taking in a full table
+// allocates from many threads at once, which glibc's allocator handles
+// less well and musl's, in the static build, much worse.
+#[cfg(not(target_env = "msvc"))]
+#[global_allocator]
+static ALLOCATOR: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
+
 /// A BGP speaker.
 #[derive(Parser, Debug)]
 #[command(version)]
diff --git a/docs/content/docs/getting-started/installation.md b/docs/content/docs/getting-started/installation.md
index 369de26..7ab850c 100644
--- a/docs/content/docs/getting-started/installation.md
+++ b/docs/content/docs/getting-started/installation.md
@@ -14,6 +14,9 @@ Cargo, or build a container image with the provided `Dockerfile`.
 
 - A stable Rust toolchain from [rustup.rs](https://rustup.rs). The container
   image uses Rust 1.92.
+- A C compiler and `make`, to build the jemalloc memory allocator that the
+  daemon uses (for example `build-essential` on Debian and Ubuntu,
+  `base-devel` on Arch Linux, or the Xcode command line tools on macOS).
 - Linux, for kernel route installation. On other operating systems, Ferrix
   operates as a BGP speaker only and does not modify forwarding.