Linux Performance & Troubleshooting

What does lowering a process's nice value actually change?

• AIts relative weight when competing for CPU, which only matters while cores are contended
• BIts reserved share of CPU time, which the scheduler guarantees whatever else is running
• CIts maximum runtime per scheduling period, after which it is stopped until the next one
• DIts placement priority, so the scheduler prefers cores that are currently unoccupied

What distinguishes a major page fault from a minor one?

• AThe major fault has to read from a backing device; the minor one is satisfied from RAM
• BThe major fault touches an unmapped address; the minor one touches a mapped page
• CThe major fault happens in kernel space; the minor one happens in userspace code
• DThe major fault kills the process; the minor one is retried transparently by the kernel

What time does the await column in iostat cover?

• AQueue time plus service time — the full wait from issue to completion of a request
• BService time only — the interval the device itself spent working on the request
• CQueue time only — the interval before the device began working on the request
• DCompletion time only — the delay between the device finishing and the caller waking

What does the x-axis of a flame graph represent?

• AThe population of sampled stacks, sorted alphabetically to merge identical frames
• BThe passage of time, so a frame's horizontal position shows when it was executing
• CThe call order within each stack, from the first function called to the most recent
• DThe cumulative cost, so frames are placed left to right from cheapest to most expensive