Dell Latitude DPC Latency Issues

Poll should have an option - no issues?

I mean all devices active, BT ON, Intel 5300 ON, all other devices are on, updated to all latest drivers. With Wifi ON though, i'm averaging 1000ms (almost all yellow bars - very seldom red bars (1 or 2 @2500ms) ), when wifi OFF though, avg is 200ms, with sometime getting closer to 900 for short period of times. There is a novatel express card cell modem plugged in.

 

hmmm... funny, disabled eSATA in BIOS. After restart windows tried to install drivers for "ISATAP" but failed... everything was green for a minute or so but then yellow and red spikes came back. Went back to enable eSATA and after that things ran smoothly on green for a minute or two again then a few yellow spikes and a red spike. Seems much more inconsistent then before, but some spikes still there but much less occasionally then before...

 

I just got my Outlet E6400 yesterday and I also had the dreaded high DPC latency issue. Roughly every 15-20 seconds I would get 3 red spikes at around 30,000, one time it went up to almost 150,000. I did some reading in these threads and saw that it could not be pinned down to any one thing. I even switched from AHCI to ATA mode and that still did not seem to take care of the issue.

I started looking at the various driver versions on Dell's site and I noticed that for the Dell-branded wireless cards, even though the version has gone through several revisions, the core Broadcom driver in the package has remained the same from the beginning. I did a little searching for my card's Broadcom model number 4322AG - I have the Dell 1510 agn card and I found a driver on HP's site for this same chipset that looked like a different version. It's located here: http://h10025.www1.hp.com/ewfrf/wc/...&dlc=en&cc=us&lang=en&os=2093&product=3744020 I had to uninstall the Dell driver then manually point it to the bcmwl6.inf file within the HP package that I unzipped using 7-zip. It connected right up to my wireless lan and lo and behold the red spikes are now almost completely gone. I have been running the DPC latency checker for about 15 minutes and only one red spike of 2061 has shown up. Something to try for those of you with Dell wireless cards.

 

updating the broadcom driver like pbow stated above eliminated most of the latency spikes for me as well.. but most importantly, the startup sound from welcome screen doesn't skip or lag anymore. after the driver update, however, the battery power dropped from 100% to 95% for no reason (while on ac.) it did recharged ok..

 

For people trying to diagnose their DPC latency issues, you should get the Windows Performance Toolkit:

http://msdn.microsoft.com/en-us/library/cc305187.aspx

Here are instructions for how to capture detailed data about DPC latency:

http://msdn.microsoft.com/en-us/library/cc305215.aspx

 

mgrier - this is actually the first I've seen xperf, and it looks awesome. Installing it and running it should be a requirement for anyone reporting DPC latency or similar issues. Unlike Thesycon's DPC Latency Checker, it monitors per CPU, and shows which modules are responsible for the latency.

Those MSDN links are a little difficult to follow, especially when running it for the first time. Two additional links I just found are http://blogs.msdn.com/ntdebugging/archive/2008/04/03/windows-performance-toolkit-xperf.aspx and http://blogs.msdn.com/peterwie/archive/2008/10/06/measuring-dpc-time.aspx .

 

Attached are my results from xperf, which clearly show iaStor.sys being the primary cause - at least in my case.

This is after I just reinstalled the 8.7 IMSM drivers while in AHCI mode, and Thesycon's DPC Latency Checker reports pegged latency times of 10+ ms.

This MSDN blog post noted on an example there that:

Shown in my screenshot and CSV export below, one of iaStor.sys's functions averages 3,343 microseconds! Unfortunately, unless someone knows if and where there are debug symbols available for this driver, only someone at Intel is going to be able to explain what that function reference is.

 

I have no such luck. The problem with my laptop is some "Unknown" module which averages 3,356 microseconds (see attached figure at the bottom). So I cannot confirm that it's the same issue. But the average duration is very similar, which arises some suspicions. I will definitely contact Dell and Intel on this during the weekend.

It would be very helpful to get feedback from other people on this. Here's a step-by-step guide to produce figures similar to mine and ziesemer's:

1) Go to this link
2) Click the appropriate link on the right side, under "Download" (x86 for 32-bit systems, x64 for 64-bit systems)
3) Run the downloaded file, choose "typical" and install on default directory (feel free to choose your own directory if you're comfortable with that)
4) Open the Start Menu, and on the lower-left search box, type cmd, but DO NOT PRESS ENTER
5) An entry named "cmd.exe" should appear on the top-left of the Start Menu. Right click it, and select "Run as administrator". You might need to supply an administrator password, do so if needed.
6) Go to the directory into which you installed the Performance Toolkit. If you installed on the default directory, type this in the command window:
6a) cd ..
6b) cd ..
6c) cd "Program Files"
6d) cd "Microsoft Windows Performance Toolkit"
7) Start running the performance toolkit. It will collect information on the latency of your system. To do that, type the following on the command window: xperf -on latency
8) Wait a few seconds (10 should be enough), then stop the performance toolkit. To do that, type this on the command window: xperf -stop
9) Now we will read the data. Type xperfview \kernel.etl. A window called "Windows Performance Analyzer" should appear.
10) Click the "Trace" menu and select "Load Symbols".
11) Scroll down to find a panel named "DPC CPU Usage". Right-click it and select "Summary Table".
12) You should now have a window similar to the ones ziesemer and I have shown here. Click "Actual Duration" to sort the entries with the one with the most latency on top.
13) Expand the topmost one by clicking on its "+" icon on the left.
14) Press Printscreen on your keyboard
15) Open Paint from the start menu (type "Paint" in the search box, then press Enter)
16) Press Control-V on your keyboard
17) Save the file and attach it to a post in this thread!

It's really much easier than it looks, I just wanted to break it down into really small and easy pieces. And if you cannot do it, post here and we'll help!

 

HerrKaputt:

If you just stop the kernel logger, the trace doesn't necessarily contain all the information needed to identify images and drivers.

When you're done, use this command to stop the loggers and merge image/process data into the trace:

xperf -d dpclatency.etl

try that and also configure your symbols as described to pick up symbols from the Microsoft symbol server:

http://msdn.microsoft.com/en-us/library/cc305211.aspx

if you don't want to read the whole thing just do this in the cmd window before viewing the data:

set _NT_SYMBOL_PATH= srv*C:\symbols*http://msdl.microsoft.com/downloads/symbols

 

OK, thanks for the tip. I'll try it and update my step-by-step list above.