LatencyMon Guide: Identify Driver Latency Causing Stutters in Windows

If your PC has been stuttering, your audio popping, or games and video calls suddenly juddering even though the CPU and GPU look fine in Task Manager, the real culprit is often invisible: kernel-level interrupts and deferred work caused by a misbehaving driver or background component — and the free tool LatencyMon can show you exactly which one.

Background / Overview​

LatencyMon is a small, free Windows utility from Resplendence designed to measure the tiny, high-priority events inside Windows that break real‑time workloads: Interrupt Service Routines (ISRs), Deferred Procedure Calls (DPCs), and hard page faults. It was built to help audio professionals confirm whether a machine is suitable for real‑time audio, but its telemetry—maximum and cumulative ISR/DPC execution times plus driver attribution—makes it a powerful general‑purpose diagnostic for everyday performance issues too.
At a high level:

• ISRs run immediately when hardware interrupts the CPU and must finish very quickly.
• DPCs are the “follow-up” work scheduled by ISRs so the kernel can return to user-mode tasks faster.
• Hard page faults occur when the OS must fetch memory from disk, interrupting execution for milliseconds to seconds.

When a driver’s ISR or DPC runs too long, or when frequent hard page faults occur, the system can’t service other time‑sensitive work and users notice stutters, audio dropouts, frame time spikes, and even temporary freezes. LatencyMon quantifies those micro‑events and attributes them to specific binaries so you can move from guesswork to targeted remediation.

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How LatencyMon works — the technical essentials​

LatencyMon runs as a monitoring tool with administrator privileges and samples kernel timer latencies, ISR and DPC durations, and hard page faults over a test interval. The program reports both the highest single execution times and aggregated totals so intermittent but severe spikes become visible even if they’re rare. That combination of peak and aggregate metrics is what makes LatencyMon particularly effective at catching problems that Task Manager and Resource Monitor miss.
Key measurements to watch:

• Highest DPC routine execution time (µs) — the longest single DPC observed.
• DPC total execution time (%) — share of CPU time spent servicing DPCs.
• ISR highest execution time (µs) — single longest ISR.
• Hard page faults — count and which process was hit most.

LatencyMon also shows the driver file names responsible for the long executions (for example, nvlddmkm.sys, dxgkrnl.sys, tcpip.sys, storport.sys), giving you a clear starting point for troubleshooting.

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What the numbers mean — thresholds and interpretation​

LatencyMon uses practical thresholds to translate raw microsecond figures into an overall verdict about whether a system is suitable for real‑time audio—and those thresholds are also useful heuristics for general responsiveness.

• If all DPC and ISR execution times stay below 2,000 µs (microseconds), the system is generally considered suitable for real‑time workloads.
• Times between 2,000 µs and 4,000 µs are considered doubtful—you may see intermittent stutters.
• Anything above 4,000 µs indicates a problem that can cause audible or visible dropouts and needs investigation.

Those cutoffs are pragmatic rather than absolute rules: a very bursty 1,900 µs driver can still cause problems if it runs frequently, while an isolated 4,100 µs event tied to a benign background task may not be as damaging in practice. Still, these ranges are a good working baseline for prioritizing fixes.

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Common culprits LatencyMon finds​

LatencyMon often points at the same classes of drivers and processes across hundreds of reports: network adapters, graphics drivers, USB and storage drivers, and OEM power/thermal frameworks.

• Network/Wi‑Fi drivers (tcpip.sys, ndis.sys or vendor .sys files): Wireless adapters frequently show up because of polling, offload interactions, or poorly optimized vendor drivers. Many users see immediate improvement when switching from Wi‑Fi to wired Ethernet during diagnosis.
• GPU drivers (nvlddmkm.sys for NVIDIA, amdkmdag.sys / atikmpag.sys for AMD, dxgkrnl.sys for DirectX kernel): GPU drivers can generate long DPCs tied to power states, hybrid GPU switching, or specific driver regressions. Community reports show nvlddmkm.sys as a recurring offender in real-world cases.
• USB controller and audio interface drivers (wdf01000.sys and vendor .sys): External audio interfaces and USB peripherals can generate high ISR/DPC activity if the controller or device firmware is misbehaving. Using a direct USB port and updating device firmware often helps.
• ACPI / OEM thermal/power drivers (ACPI.sys, Intel Dynamic Platform & Thermal Framework / DPTF): Laptops in particular can suffer DPC spikes from power-management stacks. Some forum fixes (disabling DPTF or OEM utilities) reduce latency but carry trade-offs — see the cautions below.
• Storage drivers / hard page faults (storport.sys, NVMe controller drivers): Slow disks, disks that spin down, or storage drivers with firmware bugs can cause hard page faults that produce audible clicks and stutters, especially in memory‑heavy audio workloads.

Community threads and Microsoft support boards consistently show these patterns, which is why the first triage steps often focus on networking, GPU, USB, and storage stacks.

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Step‑by‑step: run LatencyMon and interpret the report​

• Download LatencyMon from the official Resplendence site and install the Home edition. Run it as Administrator.
• Click Start and use your PC normally for at least 5–10 minutes. For intermittent problems, run it for 30 minutes or longer.
• Stop the test and check the Main/Stats tabs. Note the overall conclusion and the highest DPC/ISR execution times.
• Open the Drivers/Reported Drivers view and sort by highest execution time. That list will point to the specific drivers (file names) that caused the spikes.
• Capture screenshots and save the report for vendor or forum support. Don’t change multiple things at once—document each step and re-run LatencyMon after every change to measure impact.

This is a controlled, evidence-driven approach: find the driver with the worst numbers, test a safe mitigation (update, roll back, disable), re-run, and iterate.

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Practical fixes you can try (ranked by safety and impact)​

• Update drivers first — GPU, network, chipset, and storage drivers from the vendor or OEM page. Many DPC issues result from driver bugs that vendors fix in later releases. Use vendor utilities (NVIDIA GeForce Experience, AMD Adrenalin, Intel Driver & Support Assistant) when available.
• Switch to wired Ethernet during diagnosis — If a Wi‑Fi driver is flagged, disabling the wireless adapter often eliminates the spikes and isolates the problem.
• Clean GPU driver reinstall — Use Display Driver Uninstaller (DDU) in Safe Mode, then install the latest stable driver. This fixes corrupted driver remnants that sometimes cause DPC surges. Community threads frequently recommend this for nvlddmkm.sys problems.
• Test with integrated GPU (if present) — Boot using the iGPU or remove the discrete GPU to see if the problem migrates. If the DPC spikes disappear, the dedicated GPU driver/hardware is implicated.
• Disable unused devices — Every disabled device is one fewer potential source of latency: card readers, Bluetooth, webcams, etc. This is a safe, reversible diagnostic step.
• Switch power plan to High Performance — Set Minimum Processor State to 100% and disable USB selective suspend to minimize power-state-induced latency. On laptops, consider a temporary high-performance plan while diagnosing.
• Update BIOS/UEFI and chipset drivers — Firmware fixes can remove timing bugs and IRQ assignment issues that create spikes. Always read vendor release notes and use caution when updating firmware.
• Storage and pagefile tuning — If hard page faults dominate the report, ensure disks aren’t spinning down, check firmware, and consider increasing RAM or adjusting the pagefile. For NVMe drives, verify firmware and power settings.
• Careful rollback or controlled disabling of vendor power utilities — If ACPI.sys or OEM DPTF is implicated, some users see improvement by disabling the OEM thermal/power service temporarily. This is higher risk: it alters thermal and power protections and should be used only as a diagnostic step with a restore point.

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Advanced notes and pitfalls — what LatencyMon won’t (and can’t) fix​

LatencyMon is a diagnostic tool — it tells you which driver or process is causing latency, but it does not fix firmware bugs, hardware faults, or SMIs (System Management Interrupts) that originate in microcode or EC firmware. In particular:

• SMIs and CPU stalls: Some stalls are triggered by the platform firmware and are not attributable to a normal Windows driver call. LatencyMon can flag symptoms but not patch firmware-level faults.
• Not all reported drivers are guilty by intent: Sometimes Windows kernel files (ntoskrnl.exe, dxgkrnl.sys) show up because of interactions with third-party vendor drivers. The kernel label is a symptom, not necessarily the root cause.
• High-risk “fixes” on forums: Community-sourced “remove this OEM service” fixes sometimes reduce latency readings, but they often trade away thermal control, battery management, or other safeguards. Treat these as diagnostics, not permanent solutions, and always keep backups and restore points.

If LatencyMon points at something you don’t recognize, research the exact driver file name along with “DPC” or “ISR” before making permanent changes. The file name gives you a precise search term for vendor notes and Microsoft guidance.

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Real‑world patterns and case studies from the field​

Across forum threads and Microsoft support logs, certain recurring patterns appear:

• NVIDIA driver regressions (nvlddmkm.sys) show up as sudden increases in DPC peaks after driver updates; users often fix them with a clean reinstall, a rollback, or a BIOS update. This has been a persistent community issue for years.
• Wi‑Fi drivers spike during heavy network traffic or on certain chipset versions; switching to Ethernet immediately reduces latency in many test runs.
• OEM thermal/power frameworks (Intel DPTF) can create consistent ACPI.sys-related spikes on laptops; some users manage this by updating firmware or temporarily disabling monitoring utilities during diagnosis. Proceed with caution.
• Storage-related DPCs and hard page faults often appear on systems with aggressive power plans that let disks spin down or on systems with memory pressure; increasing RAM, disabling aggressive spin‑down, or moving large page-mapped files off busy disks helps.

These patterns are reflected in both community troubleshooting threads and official diagnostics captured in Microsoft support channels. They’re not universal, but they’re common enough to shape a pragmatic troubleshooting flow.

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A safe, prioritized checklist (what to do first, next, and last)​

Start here — safe, low-risk, high-reward actions:

• Run LatencyMon as Admin for 10–30 minutes and note the top offender.
• Update GPU, network, and chipset drivers from official vendor/OEM pages. Re-run LatencyMon.
• Test with Wi‑Fi disabled and use wired Ethernet if networking drivers show up.
• Do a clean GPU driver reinstall (DDU + fresh driver) if nvlddmkm.sys/dxgkrnl.sys show high peaks.

If the problem persists — measured, controlled, reversible steps:

• Update BIOS/UEFI and storage/NVMe firmware. Re-run LatencyMon.
• Disable nonessential OEM monitoring utilities and USB polling apps while testing.
• If storage/pagefile issues appear, ensure disks stay awake and consider adding RAM or adjusting the pagefile; avoid disabling the pagefile on systems that rely on it for crash dumps.

High-risk / last-resort options (document and have a rollback plan):

• Temporarily disabling Intel DPTF or other OEM thermal services for diagnostics (only with a known rollback and careful temperature monitoring). Use only as a controlled experiment.
• Contact the OEM/vendor with saved LatencyMon logs if firmware or deep platform issues are suspected.

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When to escalate to vendor or Microsoft support​

If LatencyMon consistently points to a single vendor driver (and driver updates/rollbacks don’t help), or if you observe enormous DPC peaks (tens of thousands of microseconds) tied to kernel modules after firmware and driver updates, escalate with:

• Saved LatencyMon reports and screenshots,
• A clear list of steps you already tried (drivers, BIOS, DDU),
• Exact driver file names and versions (shown by LatencyMon).

These artifacts make vendor or Microsoft support interactions much more productive and reduce time spent on blind troubleshooting.

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Final analysis — strengths, limits and safety warnings​

LatencyMon’s strengths are decisive: it converts invisible kernel timing behaviour into actionable data. It reveals specific drivers, shows peak execution times in microseconds, and separates ISR/DPC issues from hard page faults, enabling targeted solutions that are often far cheaper and faster than hardware upgrades.
Limitations and risks remain:

• It diagnoses but does not patch firmware or hardware faults.
• Some “fixes” recommended in public forums sacrifice power or thermal safeguards; those must be used only as temporary diagnostics with documented rollback plans.
• A single LatencyMon run is a snapshot—intermittent issues may need longer monitoring and careful reproduction steps.

A measured, evidence-first approach—run LatencyMon, update and test one item at a time, and escalate with collected logs—will resolve the majority of cases without risky system surgery.

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Conclusion​

LatencyMon is a deceptively simple but powerful diagnostic scalpel that exposes the micro‑events causing stutters, audio glitches, and lag on Windows. It brings clarity to problems that look like hardware failures but are often driver, firmware, or configuration issues. Run it for 10–30 minutes, follow a disciplined, documented remediation path, and you’ll usually find that the fix is cheaper and faster than upgrading parts. For anyone troubleshooting a slow or stuttering PC, LatencyMon should be the first tool you use — not because it fixes everything, but because it tells you, in measurable terms, exactly where to look.
If you need a concise triage plan: download LatencyMon, run it as Administrator, identify the top driver, try the corresponding safe mitigation (update/disable/roll back), and re-run. Document each step and escalate to vendor support with saved logs if the issue traces to firmware or persistent kernel-level behaviour. That disciplined workflow will save time, reduce unnecessary hardware spend, and get your PC feeling responsive again.

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Source: MakeUseOf This free tool tells you exactly what’s slowing down your PC