What is the difference between a process's RSS and VSZ?
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Quick Answer
VSZ is virtual memory reserved; RSS is the resident (physical RAM) portion actually in use.
Detailed Answer
VSZ includes mapped-but-unused memory, shared libraries, and reservations, so it overstates real usage. RSS is what's actually resident in RAM (though shared pages are counted per process). For real memory pressure, watch RSS and cgroup memory, not VSZ.
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Interview Tip
RSS reflects real RAM use; VSZ is misleading.
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