From 1d1d7431b759d5027929362bdc668ccd64db6753 Mon Sep 17 00:00:00 2001
From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Mon, 18 Oct 2010 13:03:15 -0700
Subject: [PATCH] Small utility to use free memory in a system.

For benchmarking, to take memory away from the page cache.
---
 microbench/CMakeLists.txt |  2 ++
 microbench/lockmem.c      | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 microbench/lockmem.c

diff --git a/microbench/CMakeLists.txt b/microbench/CMakeLists.txt
index 368517e..deadde4 100644
--- a/microbench/CMakeLists.txt
+++ b/microbench/CMakeLists.txt
@@ -7,4 +7,6 @@ target_link_libraries(readbench pthread rt)
 add_executable(statbench statbench.c)
 target_link_libraries(statbench pthread rt)
 
+add_executable(lockmem lockmem.c)
+
 set(CMAKE_C_FLAGS "-Wall -std=gnu99 ${CMAKE_C_FLAGS}")
diff --git a/microbench/lockmem.c b/microbench/lockmem.c
new file mode 100644
index 0000000..c0ea9d2
--- /dev/null
+++ b/microbench/lockmem.c
@@ -0,0 +1,38 @@
+/* A very simple program to lock a specified amount of memory (in megabytes)
+ * into memory.  Used to decrease the available amount of free memory on a
+ * system for benchmarking purposes. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 2) {
+        fprintf(stderr,
+                "Usage: %s <amount in MiB>\n"
+                "Locks the specified number of megabytes of RAM.\n",
+                argv[0]);
+        return 1;
+    }
+
+    size_t bufsize = atoi(argv[1]) << 20;
+    char *buf = malloc(bufsize);
+    if (buf == NULL) {
+        fprintf(stderr, "Unable to allocate buffer: %m\n");
+        return 1;
+    }
+
+    if (mlock(buf, bufsize) < 0) {
+        fprintf(stderr, "Unable to lock memory: %m\n");
+        return 1;
+    }
+
+    /* Infinite loop; simply wait for the program to be killed. */
+    while (1) {
+        sleep(3600);
+    }
+
+    return 0;
+}
-- 
2.20.1