From 680e7a382f9ea03568aceaf71f3fbb8ced83f76c Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Tue, 6 Oct 2020 08:18:42 +0100
Subject: glibc's malloc is very bad about returning memory from the kernel,
 add a call to its malloc_trim to prompt it to do so. Reported by Sarunas
 Valaskevicius.

---
 compat.h     |  4 ++++
 configure.ac | 25 +++++++++++++++++++++++++
 grid.c       |  3 +++
 3 files changed, 32 insertions(+)

diff --git a/compat.h b/compat.h
index 4efad6ee..b213336f 100644
--- a/compat.h
+++ b/compat.h
@@ -27,6 +27,10 @@
 #include <termios.h>
 #include <wchar.h>
 
+#ifdef HAVE_MALLOC_TRIM
+#include <malloc.h>
+#endif
+
 #ifdef HAVE_UTF8PROC
 #include <utf8proc.h>
 #endif
diff --git a/configure.ac b/configure.ac
index 82be9254..8f26cabd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -328,6 +328,31 @@ AC_SEARCH_LIBS(inet_ntoa, nsl)
 AC_SEARCH_LIBS(socket, socket)
 AC_CHECK_LIB(xnet, socket)
 
+# Check if using glibc and have malloc_trim(3). The glibc free(3) is pretty bad
+# about returning memory to the kernel unless the application tells it when to
+# with malloc_trim(3).
+AC_MSG_CHECKING(if free doesn't work very well)
+AC_LINK_IFELSE([AC_LANG_SOURCE(
+	[
+		#include <stdlib.h>
+		#ifdef __GLIBC__
+		#include <malloc.h>
+		int main(void) {
+			malloc_trim (0);
+			exit(0);
+		}
+		#else
+		no
+		#endif
+	])],
+	found_malloc_trim=yes,
+	found_malloc_trim=no
+)
+AC_MSG_RESULT($found_malloc_trim)
+if test "x$found_malloc_trim" = xyes; then
+	AC_DEFINE(HAVE_MALLOC_TRIM)
+fi
+
 # Check for CMSG_DATA. On some platforms like HP-UX this requires UNIX 95
 # (_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED) (see xopen_networking(7)). On
 # others, UNIX 03 (_XOPEN_SOURCE 600, see standards(7) on Solaris).
diff --git a/grid.c b/grid.c
index 96302fc3..90e1a0a5 100644
--- a/grid.c
+++ b/grid.c
@@ -265,6 +265,9 @@ grid_free_lines(struct grid *gd, u_int py, u_int ny)
 
 	for (yy = py; yy < py + ny; yy++)
 		grid_free_line(gd, yy);
+#ifdef HAVE_MALLOC_TRIM
+	malloc_trim(0);
+#endif
 }
 
 /* Create a new grid. */
-- 
cgit