hardMultiple SelectObjective-mapped
XK0-006 Practice Question: A database server running on Linux is…
A database server running on Linux is experiencing high load. The administrator runs 'strace -p <pid>' and sees many 'epoll_wait' and 'futex' calls. Which THREE of the following are possible causes of the high load? (Choose THREE.)
⚠ Common exam trap
The trap here is that candidates may incorrectly associate 'futex' calls solely with memory issues or CPU scaling, rather than recognizing them as indicators of thread contention and I/O waiting under high concurrency.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Disk I/O contention causing processes to wait.
'epoll_wait' indicates the process is waiting for I/O events, and 'futex' calls are used for synchronization. Disk I/O contention can cause the database process to block on these system calls, leading to high load as the kernel schedules other tasks while waiting for I/O to complete.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Disk I/O contention causing processes to wait.
Why this is correct
Waiting on I/O increases load average as processes are in uninterruptible sleep.
- ✓
A large number of concurrent connections.
Why this is correct
Many connections lead to context switching and contention.
- ✗
CPU frequency scaling is set to powersave.
Why it's wrong here
Powersave would reduce CPU speed, potentially lowering load but causing performance issues.
- ✗
A memory leak in the database process.
Why it's wrong here
Memory leak would cause swapping, not necessarily the observed syscalls.
- ✓
Inefficient database queries causing high CPU usage.
Why this is correct
Inefficient queries increase CPU usage, visible via strace.
Go deeper
Related to this question
Learn chapter
Linux Fundamentals and History
Key term
Kernel
The kernel is the core program of an operating system that manages hardware resources and provides essential services for all other software to run.
Key term
Linux
Linux is an open-source operating system that manages computer hardware and software, widely used in servers, desktops, and embedded systems.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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