Dell Latitude DPC Latency Issues

geodaddi - use the Microsoft's xperf tool, which was first discussed starting with response #35 in this thread. It will tell you exactly what is spending all your DPC cycles.

 

Here is my take on this whole mess that just refuses to go away. After reading all the posts here and elsewhere I had to summarize what I have found and hope might be of help to others trying to pinpoint the issue on their systems.

My System Specs:
Latitude E6400 - P8600/4GB/Intel GMA/WifiLink5300AGN
OS : Windows 7 RC Build 7100 64 Bit
All default MS driver except for
DCP_Driver for that Broadcom USH Fingerprint Reader(Vista 64 Bit)
Dell Bluetooth Driver(Vista 64 Bit)
Dell Touchpad Driver(Vista 64 Bit)
Intel Wifi 5300 AGN Driver (64 Bit ver. 12.4.0.21)

Basically there are 2 parts to identifying the dpc latency issue on ones system. They are as follows:

1. DPC Latency Checker from http://www.thesycon.de/dpclat/dpclat.exe
2. Microsoft Windows Performance Toolkit (Xperf and Xperfview)

First Method : DPC Latency Checker (dpclat.exe)

The DPC Latency Checker is a graph that tells you whether or not an issue is present on your system. One may use the trial and error method of disabling devices one at a time in Device Manager and referring back to dpclat graph to isolate the troublesome device and it's corresponding driver.

Using this method I have arrived at the conclusion that the culprit atleast on my system is the Intel Wifi Link 5300 AGN wireless adapter.

This is the dpclat screenshot with dpc spikes:



This is the dpclat screenshot after disabling the 5300 AGN adapter in device manager:




Second Method : Windows Performance Toolkit (WPT)

Ok. This method is a bit more tricky. I still don't quite grasp many of the things within. You will come across new terms and tools that you may not come across if you are not a developer(I'm not). I just blindly(most of the time) followed steps given in posts on this thread itself and some external links.

Some useful links:

http://blogs.msdn.com/peterwie/archive/2008/10/06/measuring-dpc-time.aspx (most helpful but not to be followed every step of the way)

http://msdn.microsoft.com/en-us/library/cc305211.aspx (some help for getting symbols working)

http://social.msdn.microsoft.com/Forums/it-IT/wptk_v4/thread/f7187636-c7b6-4240-9190-8ec08186f2c6 (very revealing thread regarding WPT on Win 7)

http://www.microsoft.com/downloads/...7f-5f1e-4e54-a331-c32285cdde0c&displaylang=en (go here to download WIndows SDK ISO which contains the working WPT 4.5, there are 3 iso, get the AMD64 version if you are running 64 bit).

If you have vista(32 or 64) you can find the WPT from Microsoft online directly. It is only around 5MB. On the other hand, if you are running Win 7, you will need the Windows SDK iso(a whooping 1.3GB!) from the link above. You then may opt to extract only the WPT msi file from the cab file(I used WinRAR) and intalling only that instead of intalling the entire SDK.
For example, I downloaded the AMD64 iso(GRC1SDKX_EN_DVD.iso) in the above link and found the WPT installer(FL_xperf_x64.msi_all_enu_7B3049DC_F9EE_4491_AF0A_DEDF77D59544) in the cab file (\Setup\WinSDKTools_amd64\cab1.cab) and extracted it with WinRAR to my desktop. I then renamed the extracted file to FL_xperf_x64.msi and installed.

These are the steps I took to get a tracelog and then the summary tables:

Run as administrator , All Programs> Accessories > command prompt

cd /
set _NT_SYMBOL_PATH= srv*c:\symcache*http://msdl.microsoft.com/download/symbols
xperf -on Latency
xperf -d merged1.etl (can give any name)
xperfview merged1.etl

After the last step you should get the Windows Performance Analyzer. Click on the Trace in the menu and select "Load Symbols". Now scroll down to the graph that says DPC CPU Usage and right-click and select "Summary Table"

Following is my Summary Table with wifi enabled:



Following is the same table with wifi adapter disabled in Device Manager:



As can be seen in the above summary tables, with Wifi enabled, the function "ndisMTimerObjectDpc" from the module "ndis.sys" seems to be the culprit.

So where do I go from here? Unfortunately, I don't know what else to do except to wait for intel/dell/microsoft to release new driver.

I'll grateful if someone could tell me how to file a bug report with Microsoft.

 

So I've been doing some tests using xperf to find out what is causing my irregular DPC readings. I've been getting DPC readings that fluctuate between 20-50 up to 350-400 with regular spikes around 1000. My system is a Dell Latitude E6400, 4gb ram, P8400, Nvidia Quadro 160M, Intel 5100 wireless, Dell Bluetooth, WDC HD. Running Vista Business 32 bit.

All conventional tweaks have been tried and applied. I really can't think of anything I haven't tried.

The first tests were done with DPC checker off and FW bus and soundcard on (card is a Saffire Focusrite LE which connects using FireWire). Result: 1394ohci, the native Windows FW driver is causing the spikes.

Second test is DPC on and FW bus & soundcard off. Result: DPC is causing the spikes.

Third test was done using a FW driver from AVT with DPC on and FW bus & soundcard on (http://www.alliedvisiontec.com/avt-products/software/avt-1394-bus-driver-package.html). Result: DPC seems to be the one causing spikes.

Fourth test was done with FW bus on, soundcard on no DPC checker, still using the AVT FW driver. Result: not much going on DPC wise. TCPIP is generating the highest reading. But it seems to negligible and no cause for concern.

So I have some questions for you which I really hope you can answer:

Can it be true that the native Windows FW driver can generate such a high reading?

Can it be true that DPC Latency checker can generate such a high reading?

Are the xperf readings exact?

Have you ever heard of DPC generating a high reading and then showing the result itself?

Why is the WIN FW driver causing these spikes? And again, is the reading correct/accurate?

Any input would be greatly appreciated.

I've included screenshots of all the tests.

 

Disclaimer: I'm not an expert, just a fellow E6400 owner with dpc issues

1. Yes. I used to think that MS's default driver is the best interms of stability and performance but may not be the case on all instances. In my example(the post before your's), I am having the dpc issue with the Intel 5300 AGN adapter. I have tried MS's default driver, Intel's and even Dell's. All give the same periodic(every 10ms) dpc spike.

2. DPC Latency Checker generating dpc spike is a new one. I have yet to replicate this on my system. I'm running Win 7 64 bit (build 7100).

3. I think Xperf is more reliable than DPC Latency Checker gui. As per the reading/figures you get in xperf, sorry I'm not sure I am qualified to say if they are valid or not.

4. Hahaha...it is like you calling a plumber to check for leak and he goes and breaks something and makes the leak even worst. Then he says yes there is a leak, a HUGE leak. Sorry, couldn't resist. Anyways, I've not seen this on my system.

5. I think it is safe to say MS default drivers do not guarantee problem free operation as demonstrated in my problem. There are multiple cases of this happening. Another example of this on my E6400 is the graphics driver(Intel GMA), I used to run the MS default driver. That is until I discovered that my screen brightness (Fn + Up/Down arrow) was not behaving as it should. Neither did the driver downloaded from Intel directly. Only the Dell's version worked properly.

Just my 2 cents.

 

I also don't consider myself an expert with DPC, but my guess is that the "DPC Latency Checker" and xperf are working a bit differently.

xperf is reporting results directly from the Windows kernel.

The DPC Latency Checker is generating DPC's (deferred procedure calls), and measuring and reporting how long it takes for them to complete.

So I would say that yes, the DPC Latency Checker could contribute to the DPC latency, though I'm not sure how much it should be generating "spikes" - unless they are minor and happen to match the timing interval in which the checker is testing.

 

I'm noticing pretty darn stuttery WMP performance every time i try to play music, could this have something to do with it? It stutters at the same pace, throughout....quite frustrating!

 

Hi,

can somebody please test the following: download PowerMizer Switch v1.2 and execute it as Administrator. Select either of the Powermizer off settings and restart. Since then I have no longer the latency problem.
(only when switching wireless/bluetooth on and off)

Quadro FX 3700m
ATA mode (will try the other modes today)
Windows 7
Geforce 191.07 (will also try 191.56/186.21/186.81)
No Matrix driver as in ATA mode
eSata disabled

 

I could verify it with different driver versions and ATA mode settings. The problem (latency spike) appears when powermizer lowers the gpu frequency. With powermizer disabled (use powermizer switch v1.2) I no longer have problems

PS: Do NOT install the Matrix Storage driver as I had massive problems (latest version) but no without it and update to audio driver A11.

 

I just posted an update on DPC latency in the 1737 on the Dell Forums.

Sorry. I posted too quickly. Did not realize this was a Latitude thread. Update applies to 1737 only.

 

No problem. Google for "Dell latency" and you come to this thread first. I'm sure there are shared factors (eg the Dell wireless card).

John