[PATCH pve-ha-manager 2/2] fix #7974: env: pve2: set dynamic service mem value to host memory usage

[Dominik Rusovac <d.rusovac@proxmox.com>]

Make memory accounting in dynamic CRS consistent.

Atm the imbalance value that triggers rebalancing is derived from the
guests' host memory usage, which corresponds to the respective host-side
cgroup footprints of the guests. However, the scheduler's decision
procedure predicts the changes in imbalance caused by migration
candidates based on memory usage (inside the guests). This discrepancy
can lead to oscillating migrations, as described in detail in [0].

For VMs, host memory usage is the relevant stat, as it better describes
the actual cost of running on a node than memory usage. Host memory
usage is not available for containers, so fall back to memory usage for
containers.

[0] https://bugzilla.proxmox.com/show_bug.cgi?id=7974

Signed-off-by: Dominik Rusovac <d.rusovac@proxmox.com>
---
 src/PVE/HA/Env/PVE2.pm | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/PVE/HA/Env/PVE2.pm b/src/PVE/HA/Env/PVE2.pm
index 782d19d..5f195da 100644
--- a/src/PVE/HA/Env/PVE2.pm
+++ b/src/PVE/HA/Env/PVE2.pm
@@ -46,6 +46,7 @@ use constant {
     RRD_VM_INDEX_CPU => 6,
     RRD_VM_INDEX_MAXMEM => 7,
     RRD_VM_INDEX_MEM => 8,
+    RRD_VM_INDEX_MEMHOST => 15,
 };
 
 # rrd entry indices for PVE nodes
@@ -598,11 +599,14 @@ sub get_dynamic_service_stats {
         # NOTE the guests' broadcasted vmstatus() caps maxcpu at the node's maxcpu
         my $maxcpu = ($rrdentry->[RRD_VM_INDEX_MAXCPU] || 0.0) + 0.0;
 
+        # designated fallback for containers
+        my $mem = $rrdentry->[RRD_VM_INDEX_MEMHOST] // $rrdentry->[RRD_VM_INDEX_MEM];
+
         $stats->{$sid}->{usage} = {
             maxcpu => $maxcpu,
             cpu => (($rrdentry->[RRD_VM_INDEX_CPU] || 0.0) + 0.0) * $maxcpu,
             maxmem => int($rrdentry->[RRD_VM_INDEX_MAXMEM] || 0),
-            mem => int($rrdentry->[RRD_VM_INDEX_MEM] || 0),
+            mem => int($mem || 0),
         };
     }
 
-- 
2.47.3