Dell Latitude DPC Latency (2014)

HI, I can see there's a closed thread last updated in 2011 - but I've just bought a Dell Latitude E7440 and am having exactly the same issues with trying to run music making software. I've got the LatencyMon software running and its giving me some scary red stuff:



I don't have the Intel Matrix Storage Manager, but I do have an Intel Control Center ..
I tried disabling RAID but that breaks everything because its running off an SSD.
I switched to AHCI and started getting "Invalid Partition Table" on startup.

What can I do?! (This is insanity...)

EDIT: Latest news is that I stripped Windows to the bone last night and it did not fix the issue. But Dell have offered me a motherboard replacement to fix my other problem of a USB3 hard drive not working properly .. perhaps the two issues are related; I certainly hope so ..

 

I've just run LatencyMon on my E7440 and get something similar.



However, I also ran DPC Latency Checker which has, the past, revealed significant latency issues with some of my previous notebooks. However, it gives my E7440 a clean bill of health.



I'm running Windows 7 without UEFI enabled. I had also switched from RAID (actually IRST) to AHCI at some stage but without any problems that I can recall (the Dell installation of Windows includes the drivers for the different access modes).

John

 

Thanks John, yea me too .. I initially ran the dcplat program and thought nothing was wrong; I haven't seen a yellow or red warning in that yet .. but then I tried LatencyMon and it shows spikes and problems ... Interesting to see your pagefault resolution time is not as bad as mine as for me it is the first thing to go through the roof each time I use LatencyMon, a little while later I get a spike of activity and the red warning text appears.

So I've cut windows back to the absolute minimum; 51 processes and only 1.7gb of ram being used even with Chrome open and WinMediaPlayer running - the LatencyMon shows much less activity than before; but still goes red given a minute or so .. and the performance in music making apps is still giving me clicks n pops when I push it - I'm still not able to make use of the computers full capability.

After 35 minutes of light usage I have:
Highest interrupt to process latency: 27137us
Highest ISR routine: 1800us
Highest DPC routine: 15744us
Pagefault count: 37213
Highest reported hard pagefault resolution time: 1015973us
The driver noted as having the highest interrupt to process is usbport.sys .. ISR execution time is acpi.sys.

John; you're the first person I've spoken to with one of these laptops - my computer runs great for me except: 1/ Music making programs given a fairly intensive plugin, and 2/ External usb3 hard drive stalls while transferring large files. Have you tried either of those things?

Also; just started reading your review - the keyboard backlight - I was shocked to realise that Dell have not provided a way to set the keyboard backlight time-out, they tell me its not supported : ( The only workaround is to install the unsupported Feature Enhancement Pack which allows you to set up to 5mins timeout; but the 'always on' setting doesn't work .. pain in the a$$ for somebody who bought the machine for music performance in dark environments...

 

Another longer run of LatencyMon gives me a result more like yours.



The Stats report might give a few clues about what is happening.

• Driver with highest ISR routine execution time: hal.dll - Hardware Abstraction Layer DLL
• Driver with highest DPC routine execution time: ndis.sys - NDIS 6.20 driver, Microsoft Corporation
• Process with highest pagefault count: firefox.exe

So you might want to test disabling any non-essential hardware in Device Manager to see if there are positive effects on latency.

I would also note that the pagefaults only started to appear when I went and did some web browsing while LatencyMon was running. I've got innumerable tabs open and Firefox uses >1GB RAM. However, with 12GB to play with there's no real need to use the pagefile. One test you can do is to set the page file size to zero.

Regarding the keyboard backlight timeout, I agree that it's lazy of Dell to not have a property control utility. Did you find the discussion starting here? If you can get the time up to the maximum offered of 5 minutes then that shouldn't be too bad.

John

 

My i7 E7440 behaves very well in the latency\audio\video dept., using a clean w8.1 install and disabled any service\driver\device not in use.