Dell laptop & ACPI.SYS high DPC latency problem (warning for DELL Latitude users working with low latency audio)

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LatencyMon statistics for Latitude 5491:

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CONCLUSION
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Your system appears to be having trouble handling real-time audio and other tasks. You are likely to experience buffer underruns appearing as drop outs, clicks or pops. One or more DPC routines that belong to a driver running in your system appear to be executing for too long. One problem may be related to power management, disable CPU throttling settings in Control Panel and BIOS setup. Check for BIOS updates.
LatencyMon has been analyzing your system for 0:14:22 (h:mm:ss) on all processors.

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SYSTEM INFORMATION
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Computer name: LATITUDE
OS version: Windows 10, 10.0, version 2004, build: 19041 (x64)
Hardware: Latitude 5491, Dell Inc.
CPU: GenuineIntel Intel(R) Core(TM) i5-8400H CPU @ 2.50GHz
Logical processors: 4
Processor groups: 1
RAM: 8010 MB total

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CPU SPEED
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Reported CPU speed: 2496 MHz

Note: reported execution times may be calculated based on a fixed reported CPU speed. Disable variable speed settings like Intel Speed Step and AMD Cool N Quiet in the BIOS setup for more accurate results.

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MEASURED INTERRUPT TO USER PROCESS LATENCIES
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The interrupt to process latency reflects the measured interval that a usermode process needed to respond to a hardware request from the moment the interrupt service routine started execution. This includes the scheduling and execution of a DPC routine, the signaling of an event and the waking up of a usermode thread from an idle wait state in response to that event.

Highest measured interrupt to process latency (µs): 4733.70
Average measured interrupt to process latency (µs): 9.521105

Highest measured interrupt to DPC latency (µs): 1694.90
Average measured interrupt to DPC latency (µs): 4.537061

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REPORTED ISRs
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Interrupt service routines are routines installed by the OS and device drivers that execute in response to a hardware interrupt signal.

Highest ISR routine execution time (µs): 144.028846
Driver with highest ISR routine execution time: ACPI.sys - ACPI Driver for NT, Microsoft Corporation

Highest reported total ISR routine time (%): 0.030269
Driver with highest ISR total time: ACPI.sys - ACPI Driver for NT, Microsoft Corporation

Total time spent in ISRs (%) 0.054057

ISR count (execution time <250 µs): 127085
ISR count (execution time 250-500 µs): 0
ISR count (execution time 500-1000 µs): 0
ISR count (execution time 1000-2000 µs): 0
ISR count (execution time 2000-4000 µs): 0
ISR count (execution time >=4000 µs): 0

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REPORTED DPCs
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DPC routines are part of the interrupt servicing dispatch mechanism and disable the possibility for a process to utilize the CPU while it is interrupted until the DPC has finished execution.

Highest DPC routine execution time (µs): 1785.074519
Driver with highest DPC routine execution time: ACPI.sys - ACPI Driver for NT, Microsoft Corporation

Highest reported total DPC routine time (%): 0.194360
Driver with highest DPC total execution time: Wdf01000.sys - Kernel Mode Driver Framework Runtime, Microsoft Corporation

Total time spent in DPCs (%) 0.466940

DPC count (execution time <250 µs): 1082876
DPC count (execution time 250-500 µs): 0
DPC count (execution time 500-10000 µs): 3531
DPC count (execution time 1000-2000 µs): 282
DPC count (execution time 2000-4000 µs): 0
DPC count (execution time >=4000 µs): 0

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REPORTED HARD PAGEFAULTS
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Hard pagefaults are events that get triggered by making use of virtual memory that is not resident in RAM but backed by a memory mapped file on disk. The process of resolving the hard pagefault requires reading in the memory from disk while the process is interrupted and blocked from execution.

NOTE: some processes were hit by hard pagefaults. If these were programs producing audio, they are likely to interrupt the audio stream resulting in dropouts, clicks and pops. Check the Processes tab to see which programs were hit.

Process with highest pagefault count: avp.exe

Total number of hard pagefaults 10432
Hard pagefault count of hardest hit process: 5150
Number of processes hit: 86

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PER CPU DATA
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CPU 0 Interrupt cycle time (s): 24.618683
CPU 0 ISR highest execution time (µs): 144.028846
CPU 0 ISR total execution time (s): 1.798619
CPU 0 ISR count: 118976
CPU 0 DPC highest execution time (µs): 1785.074519
CPU 0 DPC total execution time (s): 13.375219
CPU 0 DPC count: 833606
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CPU 1 Interrupt cycle time (s): 6.087548
CPU 1 ISR highest execution time (µs): 109.540865
CPU 1 ISR total execution time (s): 0.065274
CPU 1 ISR count: 8109
CPU 1 DPC highest execution time (µs): 1176.645032
CPU 1 DPC total execution time (s): 1.387714
CPU 1 DPC count: 109016
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CPU 2 Interrupt cycle time (s): 4.519612
CPU 2 ISR highest execution time (µs): 0.0
CPU 2 ISR total execution time (s): 0.0
CPU 2 ISR count: 0
CPU 2 DPC highest execution time (µs): 231.847756
CPU 2 DPC total execution time (s): 0.720195
CPU 2 DPC count: 77282
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CPU 3 Interrupt cycle time (s): 4.016975
CPU 3 ISR highest execution time (µs): 0.0
CPU 3 ISR total execution time (s): 0.0
CPU 3 ISR count: 0
CPU 3 DPC highest execution time (µs): 571.329327
CPU 3 DPC total execution time (s): 0.616966
CPU 3 DPC count: 66785
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Long story short: Dell's own hooks for ACPI.SYS are significantly slower in comparision with other manufacturers. I've compared speed of DPC executon of [ACPI.SYS] related calls on two Latitude models with other manufacturer's laptops/PCs (HW ussually older and cheaper than Dell). The execution of ACPI.SYS hooks on other brand's hardware is faster by factor of 10x - 1000x. Because of Dell's laptop DPC times it is problematic to use such hardware with appliactions handling real-time audio (regardless to ASIO settings).
My findigns might be easily verified on the internet, even in the Dell Community Forum.
I would like to have refund on my purchase as Dell did not mention inappropriateness of some Dell laptop models for low-latency audio applications.

NEW DELL XPS 17 (2020) 9700 DPC LATENCY
https://www.youtube.com/watch?v=yWrHzLtmdzg

Dell G7 7588 i7 8750H DPC latency
https://www.youtube.com/watch?v=9DZejkIcaVA

https://www.dell.com/community/Inspiron/DPC-latency-ACPI-SYS-Testing-some-questions-for-dell-employees/m-p/7739018#M101850 nobody answers

same Problem @ my Latitude 5501...

I've uninstalled all ACPI drivers in device manager.

WIN + R -> devmgmt.msc

Node: Batteries -> MS ACPI Battery blabla

Node: system devices -> ACPI- *

after reboot, ACPI has max 307 µs  @ LatencyMon and no audio dropouts until now.

Im happy

I hope this works for you too!

Hi,

I'm not conviced that uninstalling is a good solution. What happens with the power management than? Does Windows install the Windows driver instead of Dell drivers? Does the power management works properly after uninstalling?

Regards
Harald

I've arrived to the same conclusion that Dell's pre-installed Windows handles ACPI.sys differently than other manufacturers. I'm having the same latency issues causing problems with distorted/crackling with my audio interface.

Could reduce the lagacy of my DELL Latitude 5580 with Windows 11 by changing in the extended energy saving options the "PCI Express" "Connectionstate-Energy Management" for Accu and Power usage to "Moderate Power Savings" or "Off".
After that, my sound problems (cracks) disapeared.

dsp8487, how could that be done ? After a reboot everything uninstalled comes back.

I've been struggling with this issue for over 8 months. I bought Dell XPS 9510 in December 2021, and now in August 2022, still cracks. I spent about 150 hours of "support" with dell in mails and in WhatsApp. Each time with a new "supporter", I explained numerous times what the issue with crackling and latency  was, and all they managed to do was recommend OS reinstall (which I did 6 times), motherboard exchange (which I also did twice), no help, driver reinstall which I also did no change. Then they told me "it's a software issue, and we don't deal with those". Hours spent on nothing, and on "solutions" that don't do anything but waste time. Dell support is really one of the worsts. I event sent them movies and videos with sound crackling, but they didn't care about that. All I heard was "reinstall your OS", "reinstall your drivers", "Set your processor to 99% power usage", none of it ever worked.

However there is one thing that should help you. Apart from ACPI.SYS DPC latency, Dell also is really really, terribly so much with IRQ interupts. What might help you is set certain applications on different Cores, than others.

To me, I chose that Cores 1-11 would be my "normal cores", and Cores 12-16 would be my "work cores". You can read more about IRQ here: https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/interrupt-affinity-and-priority 

This fix will take you a long time, and it's manual, but it's worth it. Download "Microsoft Interupt Affinity Tool" from here: https://www.techpowerup.com/download/microsoft-interrupt-affinity-tool/

You will see a list of all drivers and services, by default their affinity is set to "any available core". What you must do is this:

- Find anything related to sound: "Sound output", "Intel Smart Sound for Bluetooth", "Realtek Service", "Intel High Definition", "RtkUniversal Service" anything that looks like related to sound, click "Set mask" and set it to cores 1-12.
- Find anything related to ACPI.sys, power or lid action: "System of ACPI.sys", "ACPI controller", "ACPI lid close action", "Power management", click "Set mask" and set it to cores 13, 14, 15, 16.
- If something doesn't look related to sound nor power, don't change its mask.

There is a lot of them, and sometimes they're duplicated. On my Dell XPS I found something like 30 "things" related to sounds, and around 18 "things" related to power and ACPI. 

Of course you don't have to go 12 cores sound vs. 4 cores ACPI, you can choose any ration you want. The most important thing is that these two "types" of processes work on different cores.

The program will prompt you for a reboot each time you set a mask, but that's unnecessary, click "No". Set masks for everything that looks related to sound, and related to ACPI or power management. After you check all that look interesting, then reboot. After you start, Crackling sounds should go away.

Than you for your solution, totally tired tying I have hope something finally will work.

However I think that your solution should be applied by manufacturer and driver provider, not by the clients... What the heaven with today's companies.

Everything up to date. I have problems with Presonus ioSTATION24c, previously I had problems with Seinberg UR22C - both USB-C audio fast interfaces with low latency. But not with Dell and their famous ACPI.sys conflict.

If the Linux could acquire microsoft..

Best regards

Hi,any sideeffects running without a presumably crucial service? I read that ACPI driver is required to charge your battery.