From 7d40a9f178a3b8d686b1f33bfc1f6e21a662ccb3 Mon Sep 17 00:00:00 2001
From: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
Date: Thu, 27 Apr 2023 16:08:46 +1200
Subject: [PATCH] rule-reload: Release excess memory freed during engine reload

The hot reload results in large chunks of memory being freed as the
as the old signature tables are discarded. Help the memory management
system along by telling to release as much memory as it can at this
point.

Bug: #6454.
---
 configure.ac          | 7 +++++++
 src/detect-engine.c   | 9 +++++++++
 src/suricata-common.h | 4 ++++
 3 files changed, 20 insertions(+)

diff --git a/configure.ac b/configure.ac
index 1eb054d98c..c2bed71761 100644
--- a/configure.ac
+++ b/configure.ac
@@ -220,6 +220,13 @@
             #include <sys/random.h> 
             ])
 
+    AC_CHECK_HEADERS([malloc.h])
+    AC_CHECK_DECL([malloc_trim],
+        AC_DEFINE([HAVE_MALLOC_TRIM], [1], [Use malloc_trim]),
+        [], [
+            #include <malloc.h> 
+            ])
+
     OCFLAGS=$CFLAGS
     CFLAGS=""
     AC_CHECK_FUNCS([strlcpy strlcat])
diff --git a/src/detect-engine.c b/src/detect-engine.c
index 0fc2df6869..25e76445ed 100644
--- a/src/detect-engine.c
+++ b/src/detect-engine.c
@@ -4797,6 +4797,15 @@ int DetectEngineReload(const SCInstance *suri)
     SCLogDebug("old_de_ctx should have been freed");
 
     SCLogNotice("rule reload complete");
+
+#ifdef HAVE_MALLOC_TRIM
+    /* The reload process potentially frees up large amounts of memory.
+     * Encourage the memory management system to reclaim as much as it
+     * can.
+     */
+    malloc_trim(0);
+#endif
+
     return 0;
 }
 
diff --git a/src/suricata-common.h b/src/suricata-common.h
index 4aad25a252..297a6fc452 100644
--- a/src/suricata-common.h
+++ b/src/suricata-common.h
@@ -212,6 +212,10 @@ typedef unsigned char u_char;
 #include <netdb.h>
 #endif
 
+#if HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
 #if __CYGWIN__
 #if !defined _X86_ && !defined __x86_64
 #define _X86_
-- 
2.47.2