Linux guest OS swap metrics report zero in VMware Aria Operations

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

Linux virtual machines monitored in VMware Aria Operations may show a value of 0 for specific memory swap metrics even when the guest operating system indicates active swap usage. This article explains why this occurs on modern Linux distributions and provides alternative monitoring methods.

Symptom The following metrics consistently report a value of 0:

• Memory | Swap In Rate (KBps)
• Memory | Swap Out Rate (KBps)
• Memory | Swapped (KB)

However, the metric Guest | Remaining Swap Space (KB) shows fluctuations, and the guest OS free -m or top commands confirm swap is being utilized.

Environment

VMware Aria Operations 8.18.x 

Cause

Modern Linux kernels utilize cgroups v2, which changes how memory and swap accounting are exposed to the system. The legacy guest metrics collected by the vCenter adapter via VMware Tools rely on older kernel counters that are no longer populated in the same way, leading the adapter to report 0 for rate-based swap metrics.

Resolution

To monitor swap activity accurately on modern Linux systems, use one of the following methods:

1. Deploy VMware Aria Operations Application Monitoring (Telegraf): Deploy the Telegraf agent to the affected Linux VMs. Telegraf collects metrics directly from /proc/vmstat and /proc/meminfo, which provides accurate, high-fidelity reporting of swap rates and usage.
2. Use Block-Level Metrics: Monitor Guest | Remaining Swap Space (KB). This metric is collected differently and remains accurate for identifying the current state of the swap file/partition.
3. Dynamic Super Metrics: If calculating swap percentage via super metrics, use the Guest | Total Swap Space (KB) property (if available) as the denominator instead of a hardcoded value to ensure accuracy across differently sized VMs.

If the issue persists or metrics are missing entirely, ensure the "Performance > Modify intervals" privilege is assigned to the vCenter service account. To speak with a customer representative or a Support Engineer, see Contact Support.

Additional Information

VM Memory Usage % Discrepancies when compared to Guest OS