Description of problem:

The engine generates somewhat incorrect alerts if the HugePages reservation on the host exceeds log_max_memory_used_threshold, even if the host is not running any VMs an completely empty. Even though its a bit debatable, ideally this is a false alert and should not be generated. See reproduction steps for details.

It is somewhat easy to happen if the hypervisor is huge (i.e. 12TB on customer case) and the user has most of that memory with static hugepages for high performance VMs, without any other type of VMs there. The VMs use the HPs only.

Version-Release number of selected component (if applicable):
ovirt-engine-4.4.8.5-0.4.el8ev.noarch
vdsm-4.40.80.6-1.el8ev.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Set the cluster memory threshold to 50% to make it easier to see

engine=# select name,log_max_memory_used_threshold from cluster;
  name   | log_max_memory_used_threshold 
---------+-------------------------------
 Default |                            50
(1 row)

2. On a host with 8GB total, reserve 5G (62.5%) with HugePages

# egrep '^HugePages_|^Mem' /proc/meminfo 
MemTotal:        8151820 kB
MemFree:         1999400 kB
MemAvailable:    2187876 kB
HugePages_Total:       5
HugePages_Free:        5
HugePages_Rsvd:        0
HugePages_Surp:        0

3. Observe engine logs, even without any VM running

2021-09-22 14:14:25,295+10 WARN  [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (EE-ManagedScheduledExecutorService-engineScheduledThreadPool-Thread-14) [a52499c] EVENT_ID: VDS_HIGH_MEM_USE(532), Used memory of host host2.kvm.local in cluster Default [70%] exceeded defined threshold [50%].

4. VDSM is reporting the 70% memUsed, but also the 5 free HPs.

[root@host2 ~]# vdsm-client Host getStats
{
    ...
    "hugepages": {
        "1048576": {
            "free_hugepages": 5,
            "nr_hugepages": 5,
            "nr_hugepages_mempolicy": 5,
            "nr_overcommit_hugepages": 0,
            "resv_hugepages": 0,
            "surplus_hugepages": 0,
            "vm.free_hugepages": 5
    ...
    "memFree": 2347,
    "memShared": 0,
    "memUsed": "71",
    ...
    "numaNodeMemFree": {
        "0": {
            "hugepages": {
                "1048576": {
                    "freePages": 5
                },
                "2048": {
                    "freePages": 0
                },
                "4": {
                    "freePages": 490799
                }
            },
            "memFree": "1917",
            "memPercent": 76
        }
    },
    ...
    "swapFree": 0,
    "swapTotal": 0,
    ...
    "vmActive": 0,
    "vmCount": 0,
    "vmMigrating": 0
}


Actual results:
* Somewhat false alert is generated

Expected results:
* Don't generate this alert