Adding script for cgroup v2 memory available.sh (#41931)

* script for cgroup v2 memory available.sh

* Update content/en/docs/concepts/scheduling-eviction/node-pressure-eviction.md

Co-authored-by: Michael <[email protected]>

* Update memory-available-cgroupv2.sh

---------

Co-authored-by: Michael <[email protected]>

Author: aritraghosh

content/en/docs/concepts/scheduling-eviction/node-pressure-eviction.md

@@ -86,7 +86,8 @@ like `free -m`. This is important because `free -m` does not work in a
 container, and if users use the [node allocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
 feature, out of resource decisions
 are made local to the end user Pod part of the cgroup hierarchy as well as the
-root node. This [script](/examples/admin/resource/memory-available.sh)
+root node. This [script](/examples/admin/resource/memory-available.sh) or
+[cgroupv2 script](/examples/admin/resource/memory-available-cgroupv2.sh)
 reproduces the same set of steps that the kubelet performs to calculate
 `memory.available`. The kubelet excludes inactive_file (the number of bytes of
 file-backed memory on the inactive LRU list) from its calculation, as it assumes that

content/en/examples/admin/resource/memory-available-cgroupv2.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+# This script reproduces what the kubelet does
+# to calculate memory.available relative to kubepods cgroup.
+
+# current memory usage
+memory_capacity_in_kb=$(cat /proc/meminfo | grep MemTotal | awk '{print $2}')
+memory_capacity_in_bytes=$((memory_capacity_in_kb * 1024))
+memory_usage_in_bytes=$(cat /sys/fs/cgroup/kubepods.slice/memory.current)
+memory_total_inactive_file=$(cat /sys/fs/cgroup/kubepods.slice/memory.stat | grep inactive_file | awk '{print $2}')
+
+memory_working_set=${memory_usage_in_bytes}
+if [ "$memory_working_set" -lt "$memory_total_inactive_file" ];
+then
+    memory_working_set=0
+else
+    memory_working_set=$((memory_usage_in_bytes - memory_total_inactive_file))
+fi
+
+memory_available_in_bytes=$((memory_capacity_in_bytes - memory_working_set))
+memory_available_in_kb=$((memory_available_in_bytes / 1024))
+memory_available_in_mb=$((memory_available_in_kb / 1024))
+
+echo "memory.capacity_in_bytes $memory_capacity_in_bytes"
+echo "memory.usage_in_bytes $memory_usage_in_bytes"
+echo "memory.total_inactive_file $memory_total_inactive_file"
+echo "memory.working_set $memory_working_set"
+echo "memory.available_in_bytes $memory_available_in_bytes"
+echo "memory.available_in_kb $memory_available_in_kb"
+echo "memory.available_in_mb $memory_available_in_mb"