memory-monitor: Update README.md to clarify memory hierarchy and cgro…

…up limits.

Added comments to explain memory limits for containerd and services
cgroups. Simplified the list of services under the "services" cgroup.

Signed-off-by: Nikolay Martyanov <nikolay@zededa.com>

pkg/memory-monitor/README.md

@@ -12,27 +12,19 @@ So, a usual memory hierarchy in the EVE system looks like this:
 ```shell
 $ tree /sys/fs/cgroup/memory/eve -d
 /sys/fs/cgroup/memory/eve <--- is set from dom0_mem kernel argument, usually 800Mb (or 8GB for ZFS)
-├── containerd
+├── containerd <-------------- is set from ctrd_mem kernel argument, usually 400Mb
 └── services <---------------- is set from eve_mem kernel argument, usually 650Mb
-    ├── debug
-    ├── edgeview
-    ├── eve-edgeview
-    ├── guacd
-    ├── lisp
-    ├── memlogd
-    ├── newlogd
+    ├── <some services>
     ├── pillar <-------------- is set from eve_mem kernel argument, usually 650Mb
-    ├── sshd
-    ├── vtpm
-    ├── watchdog
-    ├── wlan
-    ├── wwan
+    ├── <some other services>
     └── xen-tools
 ```
 
-These limits are set within `pkg/dom0-ztools/rootfs/etc/init.d/010-eve-cgroup` script.
-The "eve" cgroup limit is set according to the `dom0_mem` kernel argument, and
-the "pillar" cgroup limit is set according the `eve_mem` kernel argument.
+These limits are set within `pkg/dom0-ztools/rootfs/etc/init.d/010-eve-cgroup`
+script. The "eve" cgroup limit is set according to the `dom0_mem` kernel
+argument, and the "pillar" cgroup (along with the parent "services" cgroup
+and all other sub-cgroups of "services" cgroup) limit is set according the
+`eve_mem` kernel argument.
 
 In its turn, the "pillar" cgroup encapsulates several processes, the most
 important of which is `zedbox`: