Use malloc_trim

free_memory.go

@@ -0,0 +1,9 @@
+// +build !linux
+
+package main
+
+import "runtime/debug"
+
+func freeMemory() {
+	debug.FreeOSMemory()
+}

free_memory_linux.go

@@ -0,0 +1,20 @@
+// +build linux
+
+package main
+
+/*
+#include <features.h>
+#ifdef __GLIBC__
+#include <malloc.h>
+#else
+void malloc_trim(size_t pad){}
+#endif
+*/
+import "C"
+import "runtime/debug"
+
+func freeMemory() {
+	debug.FreeOSMemory()
+
+	C.malloc_trim(0)
+}

main.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"os/signal"
 	"runtime"
-	"runtime/debug"
 	"syscall"
 	"time"
 )
@@ -38,7 +37,7 @@ func main() {
 		var logMemStats = len(os.Getenv("IMGPROXY_LOG_MEM_STATS")) > 0
 
 		for range time.Tick(time.Duration(conf.FreeMemoryInterval) * time.Second) {
-			debug.FreeOSMemory()
+			freeMemory()
 
 			if logMemStats {
 				var m runtime.MemStats