Add a better hugepages script

This one actually does have a function.

libvirt_hooks/hooks/better_hugepages.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+# Author: SharkWipf (https://github.com/SharkWipf)
+#
+# This file depends on the PassthroughPOST hook helper script found here:
+# https://github.com/PassthroughPOST/VFIO-Tools/tree/master/libvirt_hooks
+# This hook only needs to run on `prepare/begin`, not on stop.
+#
+# This hook will help free and compact memory to ease THP allocation.
+# QEMU VMs will use THP (Transparent HugePages) by default if enough
+# unfragmented memory can be found on startup. If your memory is very
+# fragmented, this may cause a slow VM startup (like a slowly responding 
+# VM start button/command), and may cause QEMU to fall back to regular
+# memory pages, slowing down VM performance.
+# If you (suspect you) suffer from this, this hook will help ease THP
+# allocation so you don't need to resort to misexplained placebo scripts.
+#
+# Don't use the old hugepages.sh script in this repo. It's useless.
+# It's only kept in for archival reasons and offers no benefits.
+
+
+# Finish writing any outstanding writes to disk.
+sync
+# Drop all filesystem caches to free up more memory.
+echo 3 > /proc/sys/vm/drop_caches
+# Do another run of writing any possible new outstanding writes.
+sync
+# Tell the kernel to "defragment" memory where possible.
+echo 1 > /proc/sys/vm/compact_memory