From 7628f5f51ca209cb3de752dc7ed59bdf6658e63b Mon Sep 17 00:00:00 2001
From: Wilfred Hughes <me@wilfred.me.uk>
Date: Fri, 13 Jun 2025 00:54:08 +0100
Subject: [PATCH] Switch to jemalloc, at least for now

See discussions in #805.
---
 Cargo.lock  | 41 +++++++++++++++++++++--------------------
 Cargo.toml  |  7 +++----
 src/main.rs | 23 +++++++++++++++++++----
 3 files changed, 43 insertions(+), 28 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index ba5ae41a6..6245070aa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -254,10 +254,8 @@ dependencies = [
  "ignore",
  "lazy_static",
  "libc",
- "libmimalloc-sys",
  "line-numbers",
  "log",
- "mimalloc",
  "owo-colors",
  "predicates",
  "pretty_assertions",
@@ -272,6 +270,7 @@ dependencies = [
  "streaming-iterator",
  "strsim 0.10.0",
  "strum",
+ "tikv-jemallocator",
  "tree-sitter",
  "tree-sitter-bash",
  "tree-sitter-c",
@@ -516,15 +515,6 @@ version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4ec2a862134d2a7d32d7983ddcdd1c4923530833c9f2ea1a44fc5fa473989058"
 
-[[package]]
-name = "libmimalloc-sys"
-version = "0.1.24"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7705fc40f6ed493f73584abbb324e74f96b358ff60dfe5659a0f8fc12c590a69"
-dependencies = [
- "cc",
-]
-
 [[package]]
 name = "line-numbers"
 version = "0.3.0"
@@ -559,15 +549,6 @@ version = "2.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "523dc4f511e55ab87b694dc30d0f820d60906ef06413f93d4d7a1385599cc149"
 
-[[package]]
-name = "mimalloc"
-version = "0.1.28"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b0dfa131390c2f6bdb3242f65ff271fcdaca5ff7b6c08f28398be7f2280e3926"
-dependencies = [
- "libmimalloc-sys",
-]
-
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -983,6 +964,26 @@ version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"
 
+[[package]]
+name = "tikv-jemalloc-sys"
+version = "0.6.0+5.3.0-1-ge13ca993e8ccb9ba9847cc330696e02839f328f7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd3c60906412afa9c2b5b5a48ca6a5abe5736aec9eb48ad05037a677e52e4e2d"
+dependencies = [
+ "cc",
+ "libc",
+]
+
+[[package]]
+name = "tikv-jemallocator"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4cec5ff18518d81584f477e9bfdf957f5bb0979b0bac3af4ca30b5b3ae2d2865"
+dependencies = [
+ "libc",
+ "tikv-jemalloc-sys",
+]
+
 [[package]]
 name = "tree-sitter"
 version = "0.24.5"
diff --git a/Cargo.toml b/Cargo.toml
index 71cdcfc75..6b3a270f6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -44,10 +44,9 @@ libc = "0.2.108"
 log = "0.4.14"
 pretty_env_logger = "0.5.0"
 
-mimalloc = { version = "0.1.28", default-features = false }
-# Pin libmimalloc-sys due to 0.1.25 producing a huge slowdown in very
-# large textual files, as discussed in #297.
-libmimalloc-sys = "=0.1.24"
+[target.'cfg(not(target_env = "msvc"))'.dependencies]
+tikv-jemallocator = "0.6"
+
 radix-heap = "0.4.2"
 # ignore does not declare a MSRV, but it's part of ripgrep, which has
 # a slightly more aggressive MSRV than difftastic. Constrain ignore to
diff --git a/src/main.rs b/src/main.rs
index 7278c084a..1fca0725f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -50,7 +50,6 @@ extern crate log;
 
 use display::style::print_warning;
 use log::info;
-use mimalloc::MiMalloc;
 use options::FilePermissions;
 use options::USAGE;
 
@@ -73,10 +72,26 @@ use crate::parse::syntax;
 
 /// The global allocator used by difftastic.
 ///
-/// Diffing allocates a large amount of memory, and `MiMalloc` performs
-/// better.
+/// Diffing allocates a large amount of memory, and both Jemalloc and
+/// MiMalloc perform better than the system allocator.
+///
+/// Some versions of MiMalloc (specifically libmimalloc-sys greater
+/// than 0.1.24) handle very large, mostly unused allocations
+/// badly. This makes large line-oriented diffs very slow, as
+/// discussed in #297.
+///
+/// MiMalloc is generally faster than Jemalloc, but older versions of
+/// MiMalloc don't compile on GCC 15+, so use Jemalloc for now. See
+/// #805.
+///
+/// For reference, Jemalloc uses 10-20% more time (although up to 33%
+/// more instructions) when testing on sample files.
+#[cfg(not(target_env = "msvc"))]
+use tikv_jemallocator::Jemalloc;
+
+#[cfg(not(target_env = "msvc"))]
 #[global_allocator]
-static GLOBAL: MiMalloc = MiMalloc;
+static GLOBAL: Jemalloc = Jemalloc;
 
 use std::path::Path;
 use std::{env, thread};