LCA Performance Monitoring & Tuning 5

Question 1

Which command measures and displays network interface statistics including packets, errors, and drops in real time?

Accepted Answer

Both ip -s link and netstat -i show interface statistics

Answer

Both 'ip -s link' and 'netstat -i' display per-interface packet counters; ip -s link is the modern preferred tool.

Question 2

What does 'numactl --membind' do when running a process on a NUMA system?

Accepted Answer

Restricts memory allocations to specified NUMA nodes, reducing cross-node memory latency

Answer

numactl --membind forces memory allocations to the listed NUMA nodes, improving locality for memory-intensive workloads.

Question 3

Which tool can trace kernel function calls and measure their latency using eBPF without modifying the kernel?

Accepted Answer

bpftrace

Answer

bpftrace uses eBPF programs to instrument kernel and user-space functions dynamically without kernel modification.

Question 4

A server shows high CPU steal time (st) in top. What does this indicate?

Accepted Answer

A hypervisor is consuming CPU cycles that the VM requested, indicating resource contention on the host

Answer

CPU steal time appears in virtualized environments when the hypervisor is running other guests and cannot service this VM's requests.

Question 5

What does the 'tuned' daemon do in Linux performance management?

Accepted Answer

Applies predefined and custom tuning profiles to kernel parameters, CPU governors, and disk settings automatically

Answer

tuned dynamically switches between profiles (e.g., throughput-performance, latency-performance) to optimize the system for its workload.

(LCA) Certified Linux Administrator Practice Test