memeater: consume a given amount of memory.

This seems to be a popular reinvention. There are three different
variants in the Android tree, and at least another independent one
(intended for Android) on github.

This is the minimal intersection of them all, which will hopefully
still be useful. (It's very close to the system/extras/ Android
one, but assumes that the user can just run under nohup(1) rather
than needing the tool to daemonize itself.)

There's not much motivation for the for loop rather than a call to
memset(); that was just intended as paranoia against "can something
cheat me out of my dirty pages?". This still repeats every 256
bytes, though, and I don't have any concrete example of where
duplicate page detection or compression kicks in, so although
calloc() would not be a suitable replacement, memset() might well
be.

1 files changed, 31 insertions, 0 deletions

diff --git a/toys/pending/memeater.c b/toys/pending/memeater.c
new file mode 100644
index 00000000..d4aa5f04
--- /dev/null
+++ b/toys/pending/memeater.c
@@ -0,0 +1,31 @@
+/* memeater.c - consume the specified amount of memory
+ *
+ * Copyright 2024 The Android Open Source Project
+
+USE_MEMEATER(NEWTOY(memeater, "<1", TOYFLAG_USR|TOYFLAG_BIN))
+
+config MEMEATER
+  bool "memeater"
+  default y
+  help
+    usage: memeater SIZE
+
+    Consume the specified amount of memory (in bytes, with optional suffix).
+*/
+
+#define FOR_memeater
+#include "toys.h"
+
+void memeater_main(void)
+{
+  long long size = atolx(*toys.optargs), i;
+  char* p;
+
+  p = xmalloc(size);
+  // Lock the physical pages.
+  if (mlock(p, size)) perror_exit("mlock");
+  // And ensure we weren't cheated by overcommit...
+  for (i = 0; i < size; i++) p[i] = i;
+
+  while (1) pause();
+}