CPU & Memory interview questions

69 real CPU & Memory questions from the Virtualization bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is Co-stop (%CSTP)?

Mid
  1. A.Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host
  2. B.Keeping a VM vCPUs and memory on one physical NUMA node avoids costly remote memory access.
  3. C.An ESXi reclamation tier that compresses memory pages into a per-VM cache instead of swapping them to disk, sitting between ballooning and host swapping
  4. D.An ESXi metric showing time a multi-vCPU VM was ready but stopped because its sibling vCPUs could not be co-scheduled; high values indicate oversized vCPU counts
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2. Which term means: "An ESXi metric showing time a multi-vCPU VM was ready but stopped because its sibling vCPUs could not be co-scheduled; high values indicate oversized vCPU counts"?

Mid
  1. A.NUMA node affinity
  2. B.CPU ready vs co-stop
  3. C.Co-stop (%CSTP)
  4. D.Memory reservation
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3. Which statement is correct?

Mid
  1. A.Co-stop (%CSTP) — ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  2. B.Co-stop (%CSTP) — On modern ESXi, page sharing is restricted to within a single VM by default (salted) for security, sharing identical pages only inside that VM
  3. C.Co-stop (%CSTP) — Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  4. D.Co-stop (%CSTP) — An ESXi metric showing time a multi-vCPU VM was ready but stopped because its sibling vCPUs could not be co-scheduled; high values indicate oversized vCPU counts
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4. What is vCPU?

Junior
  1. A.An ESXi metric showing time a multi-vCPU VM was ready but stopped because its sibling vCPUs could not be co-scheduled; high values indicate oversized vCPU counts
  2. B.ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  3. C.A vSphere per-VM setting that grants exclusive physical core access, disables interrupt coalescing and reduces jitter for real-time and telco workloads
  4. D.A virtual CPU presented to a guest, scheduled by the hypervisor onto physical cores/threads as a time-shared resource
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5. Which term means: "A virtual CPU presented to a guest, scheduled by the hypervisor onto physical cores/threads as a time-shared resource"?

Junior
  1. A.vCPU
  2. B.CPU scheduler relaxed co-scheduling
  3. C.Large pages (2MB)
  4. D.Memory overcommit ratio
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6. Which statement is correct?

Junior
  1. A.vCPU — Deep CPU C-states save power but add wake latency; setting host power policy to High Performance reduces this for latency-sensitive VMs
  2. B.vCPU — Two logical threads on one physical core sharing execution units; the scheduler accounts for this so a vCPU on a busy hyperthread gets less throughput
  3. C.vCPU — A virtual CPU presented to a guest, scheduled by the hypervisor onto physical cores/threads as a time-shared resource
  4. D.vCPU — On modern ESXi, page sharing is restricted to within a single VM by default (salted) for security, sharing identical pages only inside that VM
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7. What is vNUMA?

Junior
  1. A.Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host
  2. B.A vSphere per-VM setting that grants exclusive physical core access, disables interrupt coalescing and reduces jitter for real-time and telco workloads
  3. C.Deep CPU C-states save power but add wake latency; setting host power policy to High Performance reduces this for latency-sensitive VMs
  4. D.A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping
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8. Which term means: "Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host"?

Junior
  1. A.Transparent page sharing scope
  2. B.vNUMA
  3. C.Memory limit
  4. D.Co-stop (%CSTP)
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9. Which statement is correct?

Junior
  1. A.vNUMA — Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host
  2. B.vNUMA — A relative weight determining which VMs get physical memory first when the host is under contention
  3. C.vNUMA — Ready time is waiting for any pCPU; co-stop is waiting for sibling vCPUs to be scheduled together.
  4. D.vNUMA — Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
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10. What is CPU affinity?

Mid
  1. A.Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
  2. B.Pinning a VM's vCPUs to specific physical cores; rarely recommended as it breaks DRS and the scheduler's load balancing
  3. C.The ESXi technique that no longer requires all sibling vCPUs to run in perfect lockstep, only bounding their skew, reducing co-stop on wide VMs
  4. D.On modern ESXi, page sharing is restricted to within a single VM by default (salted) for security, sharing identical pages only inside that VM
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11. Which term means: "Pinning a VM's vCPUs to specific physical cores; rarely recommended as it breaks DRS and the scheduler's load balancing"?

Mid
  1. A.Hyperthreading sharing
  2. B.Memory limit
  3. C.CPU affinity
  4. D.Idle memory tax
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12. Which statement is correct?

Mid
  1. A.CPU affinity — Pinning a VM's vCPUs to specific physical cores; rarely recommended as it breaks DRS and the scheduler's load balancing
  2. B.CPU affinity — ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  3. C.CPU affinity — Exposes the host NUMA topology to large guests so the guest OS schedules threads with locality.
  4. D.CPU affinity — An ESXi mechanism that reclaims memory a VM reserved but is not actively using, charging idle pages more so active VMs get priority
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13. What is Memory reservation?

Junior
  1. A.ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  2. B.An ESXi mechanism that reclaims memory a VM reserved but is not actively using, charging idle pages more so active VMs get priority
  3. C.A virtual CPU presented to a guest, scheduled by the hypervisor onto physical cores/threads as a time-shared resource
  4. D.A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping
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14. Which term means: "A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping"?

Junior
  1. A.Memory limit
  2. B.Memory reservation
  3. C.CPU affinity
  4. D.Hyperthreading sharing
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15. Which statement is correct?

Junior
  1. A.Memory reservation — Compresses pages that would otherwise be swapped, trading CPU for far lower latency than disk swap.
  2. B.Memory reservation — Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  3. C.Memory reservation — Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
  4. D.Memory reservation — A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping
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16. What is Memory limit?

Junior
  1. A.ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  2. B.An upper cap on physical RAM a VM may consume regardless of configured size, often a cause of unexpected swapping when misconfigured
  3. C.Time a multi-vCPU VM is held so its vCPUs can be co-scheduled; high values signal vCPU oversizing.
  4. D.Compresses pages that would otherwise be swapped, trading CPU for far lower latency than disk swap.
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17. Which term means: "An upper cap on physical RAM a VM may consume regardless of configured size, often a cause of unexpected swapping when misconfigured"?

Junior
  1. A.Hyperthreading sharing
  2. B.Memory limit
  3. C.Co-stop (%CSTP)
  4. D.Latency-sensitivity high
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18. Which statement is correct?

Junior
  1. A.Memory limit — Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  2. B.Memory limit — The ratio of total configured VM memory to physical host RAM, made safe by sharing, ballooning and reclamation when actual usage is lower
  3. C.Memory limit — An upper cap on physical RAM a VM may consume regardless of configured size, often a cause of unexpected swapping when misconfigured
  4. D.Memory limit — Pinning a VM's vCPUs to specific physical cores; rarely recommended as it breaks DRS and the scheduler's load balancing
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19. What is Memory shares?

Junior
  1. A.A vSphere per-VM setting that grants exclusive physical core access, disables interrupt coalescing and reduces jitter for real-time and telco workloads
  2. B.Time a multi-vCPU VM is held so its vCPUs can be co-scheduled; high values signal vCPU oversizing.
  3. C.ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  4. D.A relative weight determining which VMs get physical memory first when the host is under contention
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20. Which term means: "A relative weight determining which VMs get physical memory first when the host is under contention"?

Junior
  1. A.Memory state thresholds
  2. B.Power management C-states impact
  3. C.Memory shares
  4. D.Memory limit
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21. Which statement is correct?

Junior
  1. A.Memory shares — Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host
  2. B.Memory shares — A relative weight determining which VMs get physical memory first when the host is under contention
  3. C.Memory shares — Time a multi-vCPU VM is held so its vCPUs can be co-scheduled; high values signal vCPU oversizing.
  4. D.Memory shares — Compresses pages that would otherwise be swapped, trading CPU for far lower latency than disk swap.
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22. What is Memory compression?

Senior
  1. A.Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  2. B.A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping
  3. C.An ESXi reclamation tier that compresses memory pages into a per-VM cache instead of swapping them to disk, sitting between ballooning and host swapping
  4. D.Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
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23. Which term means: "An ESXi reclamation tier that compresses memory pages into a per-VM cache instead of swapping them to disk, sitting between ballooning and host swapping"?

Senior
  1. A.Memory compression
  2. B.NUMA node affinity
  3. C.Power management C-states impact
  4. D.vCPU
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24. Which statement is correct?

Senior
  1. A.Memory compression — An ESXi reclamation tier that compresses memory pages into a per-VM cache instead of swapping them to disk, sitting between ballooning and host swapping
  2. B.Memory compression — Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
  3. C.Memory compression — A vSphere per-VM setting that grants exclusive physical core access, disables interrupt coalescing and reduces jitter for real-time and telco workloads
  4. D.Memory compression — Virtual NUMA topology exposed to large VMs so the guest OS and applications can make NUMA-aware memory placement decisions matching the underlying host
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25. What is Large pages (2MB)?

Senior
  1. A.ESXi escalates reclamation (ballooning, compression, swap) as free RAM crosses high, clear, soft, hard, and low marks.
  2. B.Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  3. C.A relative weight determining which VMs get physical memory first when the host is under contention
  4. D.Compresses pages that would otherwise be swapped, trading CPU for far lower latency than disk swap.
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26. Which term means: "Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down"?

Senior
  1. A.Idle memory tax
  2. B.vCPU
  3. C.CPU ready vs co-stop
  4. D.Large pages (2MB)
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27. Which statement is correct?

Senior
  1. A.Large pages (2MB) — Backing guest memory with 2MB pages to reduce TLB pressure; on ESXi this disables transparent page sharing for those pages until memory pressure forces a break-down
  2. B.Large pages (2MB) — A virtual CPU presented to a guest, scheduled by the hypervisor onto physical cores/threads as a time-shared resource
  3. C.Large pages (2MB) — On modern ESXi, page sharing is restricted to within a single VM by default (salted) for security, sharing identical pages only inside that VM
  4. D.Large pages (2MB) — Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
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28. What is Hyperthreading sharing?

Mid
  1. A.Deduplicates identical guest memory pages; restricted to intra-VM by default since cross-VM sharing posed a security risk.
  2. B.A guaranteed amount of physical RAM locked for a VM that will never be reclaimed by ballooning or swapping
  3. C.An ESXi reclamation tier that compresses memory pages into a per-VM cache instead of swapping them to disk, sitting between ballooning and host swapping
  4. D.Two logical threads on one physical core sharing execution units; the scheduler accounts for this so a vCPU on a busy hyperthread gets less throughput
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29. Which term means: "Two logical threads on one physical core sharing execution units; the scheduler accounts for this so a vCPU on a busy hyperthread gets less throughput"?

Mid
  1. A.vNUMA
  2. B.Latency-sensitivity high
  3. C.Hyperthreading sharing
  4. D.CPU affinity
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30. Which statement is correct?

Mid
  1. A.Hyperthreading sharing — Two logical threads on one physical core sharing execution units; the scheduler accounts for this so a vCPU on a busy hyperthread gets less throughput
  2. B.Hyperthreading sharing — Deep CPU C-states save power but add wake latency; setting host power policy to High Performance reduces this for latency-sensitive VMs
  3. C.Hyperthreading sharing — Pinning a VM's vCPUs to specific physical cores; rarely recommended as it breaks DRS and the scheduler's load balancing
  4. D.Hyperthreading sharing — An upper cap on physical RAM a VM may consume regardless of configured size, often a cause of unexpected swapping when misconfigured
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