From 01f8f4f074a8ca931662632bdf9e7bd889ab5b17 Mon Sep 17 00:00:00 2001
From: Martin Weinelt <hexa@darmstadt.ccc.de>
Date: Thu, 27 May 2021 04:28:01 +0200
Subject: [PATCH] nixos/matrix-synapse: allow preloading jemalloc

This is the default in the upstreams docker image and claims to reduce
memory fragmentation and usage.
---
 nixos/modules/services/misc/matrix-synapse.nix | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/nixos/modules/services/misc/matrix-synapse.nix b/nixos/modules/services/misc/matrix-synapse.nix
index dff587453042..eedb44fbe12b 100644
--- a/nixos/modules/services/misc/matrix-synapse.nix
+++ b/nixos/modules/services/misc/matrix-synapse.nix
@@ -143,6 +143,13 @@ in {
           List of additional Matrix plugins to make available.
         '';
       };
+      withJemalloc = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to preload jemalloc to reduce memory fragmentation and overall usage.
+        '';
+      };
       no_tls = mkOption {
         type = types.bool;
         default = false;
@@ -720,7 +727,11 @@ in {
           --keys-directory ${cfg.dataDir} \
           --generate-keys
       '';
-      environment.PYTHONPATH = makeSearchPathOutput "lib" cfg.package.python.sitePackages [ pluginsEnv ];
+      environment = {
+        PYTHONPATH = makeSearchPathOutput "lib" cfg.package.python.sitePackages [ pluginsEnv ];
+      } // optionalAttrs (cfg.withJemalloc) {
+        LD_PRELOAD = "${pkgs.jemalloc}/lib/libjemalloc.so";
+      };
       serviceConfig = {
         Type = "notify";
         User = "matrix-synapse";