check-health: reverse logic for RAM (free -> utilization)...

... to bring it in sync with CPU utilization.

Also make the output more verbose, at least for the warning.

---- ✂️ ----
🗃️📈️ Health warning: RAM utilization

The RAM utilization on MikroTik is at 81%!

total:          64 MiB
used:           52 MiB
free:           11 MiB
---- ✂️ ----
🗃️📉️ Health recovery: RAM utilization

The RAM utilization on MikroTik decreased to 65%.
---- ✂️ ----

6 files changed, 20 insertions, 19 deletions

diff --git a/check-health.rsc b/check-health.rsc
index af0d70b..3ada4c8 100644
--- a/check-health.rsc
+++ b/check-health.rsc
@@ -12,8 +12,8 @@
 
 :global CheckHealthCPUUtilization;
 :global CheckHealthCPUUtilizationNotified;
-:global CheckHealthFreeRAMNotified;
 :global CheckHealthLast;
+:global CheckHealthRAMUtilizationNotified;
 :global CheckHealthTemperature;
 :global CheckHealthTemperatureDeviation;
 :global CheckHealthTemperatureNotified;
@@ -52,20 +52,21 @@ $ScriptLock $0;
   :set CheckHealthCPUUtilizationNotified false;
 }
 
-:local CheckHealthFreeRAM ($Resource->"free-memory" * 100  / $Resource->"total-memory");
-:if ($CheckHealthFreeRAM < 20 && $CheckHealthFreeRAMNotified != true) do={
+:local CheckHealthRAMUtilization (($Resource->"total-memory" - $Resource->"free-memory") * 100 / $Resource->"total-memory");
+:if ($CheckHealthRAMUtilization >=80 && $CheckHealthRAMUtilizationNotified != true) do={
   $SendNotification2 ({ origin=$0; \
-    subject=([ $SymbolForNotification "card-file-box,chart-decreasing" ] . "Health warning: free RAM"); \
-    message=("The available free RAM on " . $Identity . " is at " . $CheckHealthFreeRAM . "% (" . \
-    ($Resource->"free-memory" / 1024 / 1024) . "MiB)!") });
-  :set CheckHealthFreeRAMNotified true;
+    subject=([ $SymbolForNotification "card-file-box,chart-increasing" ] . "Health warning: RAM utilization"); \
+    message=("The RAM utilization on " . $Identity . " is at " . $CheckHealthRAMUtilization . "%!\n\n" . \
+    [ $FormatLine "total" (($Resource->"total-memory" / 1024 / 1024) . " MiB") ] . "\n" . \
+    [ $FormatLine "used" ((($Resource->"total-memory" - $Resource->"free-memory") / 1024 / 1024) . " MiB") ] . "\n" . \
+    [ $FormatLine "free" (($Resource->"free-memory" / 1024 / 1024) . " MiB") ]) });
+  :set CheckHealthRAMUtilizationNotified true;
 }
-:if ($CheckHealthFreeRAM > 30 && $CheckHealthFreeRAMNotified = true) do={
+:if ($CheckHealthRAMUtilization < 70 && $CheckHealthRAMUtilizationNotified = true) do={
   $SendNotification2 ({ origin=$0; \
-    subject=([ $SymbolForNotification "card-file-box,chart-increasing" ] . "Health recovery: free RAM"); \
-    message=("The available free RAM on " . $Identity . " increased to " . $CheckHealthFreeRAM . "% (" . \
-    ($Resource->"free-memory" / 1024 / 1024) . "MiB).") });
-  :set CheckHealthFreeRAMNotified false;
+    subject=([ $SymbolForNotification "card-file-box,chart-decreasing" ] . "Health recovery: RAM utilization"); \
+    message=("The RAM utilization on " . $Identity . " decreased to " . $CheckHealthRAMUtilization . "%.") });
+  :set CheckHealthRAMUtilizationNotified false;
 }
 
 :if ([ :len [ /system/health/find ] ] = 0) do={
diff --git a/doc/check-health.d/notification-03-free-ram-low.avif b/doc/check-health.d/notification-03-free-ram-low.avif
deleted file mode 100644
index effc87c..0000000
--- a/doc/check-health.d/notification-03-free-ram-low.avif
+++ /dev/null
diff --git a/doc/check-health.d/notification-03-ram-utilization-high.avif b/doc/check-health.d/notification-03-ram-utilization-high.avif
new file mode 100644
index 0000000..59155c5
--- /dev/null
+++ b/doc/check-health.d/notification-03-ram-utilization-high.avif
diff --git a/doc/check-health.d/notification-04-free-ram-ok.avif b/doc/check-health.d/notification-04-free-ram-ok.avif
deleted file mode 100644
index cadb1d0..0000000
--- a/doc/check-health.d/notification-04-free-ram-ok.avif
+++ /dev/null
diff --git a/doc/check-health.d/notification-04-ram-utilization-ok.avif b/doc/check-health.d/notification-04-ram-utilization-ok.avif
new file mode 100644
index 0000000..d995b9a
--- /dev/null
+++ b/doc/check-health.d/notification-04-ram-utilization-ok.avif
diff --git a/doc/check-health.md b/doc/check-health.md
index 34b5faf..3bde4e9 100644
--- a/doc/check-health.md
+++ b/doc/check-health.md
@@ -13,7 +13,7 @@ This script is run from scheduler periodically, sending notification on
 health related events:
 
 * high CPU utilization
-* low available free RAM
+* high RAM utilization (low available RAM)
 * voltage jumps up or down more than configured threshold
 * voltage drops below hard lower limit
 * power supply failed or recovered
@@ -21,9 +21,9 @@ health related events:
 
 Note that bad initial state will not trigger an event.
 
-Monitoring CPU utilization and available free RAM works on all devices.
-Other than that only sensors available in hardware can be checked. See what
-your hardware supports:
+Monitoring CPU and RAM utilization (available processing and memory
+resources) works on all devices. Other than that only sensors available
+in hardware can be checked. See what your hardware supports:
 
     /system/health/print;
 
@@ -34,10 +34,10 @@ your hardware supports:
 ![check-health notification cpu utilization high](check-health.d/notification-01-cpu-utilization-high.avif)  
 ![check-health notification cpu utilization ok](check-health.d/notification-02-cpu-utilization-ok.avif)
 
-#### Available free RAM
+#### RAM utilization (low available RAM)
 
-![check-health notification free ram low](check-health.d/notification-03-free-ram-low.avif)  
-![check-health notification free ram ok](check-health.d/notification-04-free-ram-ok.avif)
+![check-health notification ram utilization high](check-health.d/notification-03-ram-utilization-high.avif)  
+![check-health notification ram utilization ok](check-health.d/notification-04-ram-utilization-ok.avif)
 
 #### Voltage