A systems administrator is troubleshooting a server that runs a database application. The server has 64 GB of RAM and 16 CPU cores. The administrator notices that the system is using a significant amount of swap space even though there is plenty of free memory. The 'free -m' command shows: total memory = 65536, used = 50000, free = 15536, buffers/cache = 10000, swap total = 8192, swap used = 6000. Which of the following is the most likely cause?
Trap 1: The vm.dirty_ratio and vm.dirty_background_ratio are set too high.
These parameters control how much dirty page cache can accumulate. High values could cause more I/O, but not necessarily swap usage.
Trap 2: The database is configured to use huge pages, which are not…
Huge pages are not swappable, so they would reduce swap usage, not increase it.
Trap 3: The vm.vfs_cache_pressure is set too low.
A low vfs_cache_pressure causes the kernel to retain filesystem cache, which would use memory, not swap. This would decrease swap usage.
- A
The vm.dirty_ratio and vm.dirty_background_ratio are set too high.
Why wrong: These parameters control how much dirty page cache can accumulate. High values could cause more I/O, but not necessarily swap usage.
- B
The vm.swappiness value is set too high.
A high swappiness value (e.g., 100) makes the kernel more likely to swap pages out to disk even when there is free memory available.
- C
The database is configured to use huge pages, which are not swappable.
Why wrong: Huge pages are not swappable, so they would reduce swap usage, not increase it.
- D
The vm.vfs_cache_pressure is set too low.
Why wrong: A low vfs_cache_pressure causes the kernel to retain filesystem cache, which would use memory, not swap. This would decrease swap usage.