Dell Latitude DPC Latency Issues

[MiB]

Originally Posted by ziesemer

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've been saying for quite some time that the primary cause are the Intel drivers.

If you're willing try this to see if it might help;

Go to Start, type System Configuration and select it.

1. In the Services tab - uncheck Intel Matrix Storage Event Monitor

2. In the Startup tab - uncheck Raid even monitor

Restart the system and restest.

To restore things back to the way they were, go back and check on those 2 boxes again.

[Circus_boi]

Originally Posted by MiB

I've been saying for quite some time that the primary cause are the Intel drivers.

If you're willing try this to see if it might help;

Go to Start, type System Configuration and select it.

1. In the Services tab - uncheck Intel Matrix Storage Event Monitor

2. In the Startup tab - uncheck Raid even monitor

Restart the system and restest.

To restore things back to the way they were, go back and check on those 2 boxes again.

I didn't have this latency issue before, but upgraded some drivers/apps from the Dell Support page yesterday (incl. Intel Matrix Storage Manager v.8.7.0.1007: A04 application and A03 Driver), and now I have > 8,000 red bars....tried this trick but no effect. Sigh....should've left well enough alone, I guess.....

[MiB]

Originally Posted by Circus_boi

I didn't have this latency issue before, but upgraded some drivers/apps from the Dell Support page yesterday (incl. Intel Matrix Storage Manager v.8.7.0.1007: A04 application and A03 Driver), and now I have > 8,000 red bars....tried this trick but no effect. Sigh....should've left well enough alone, I guess.....

Just revert back to the Intel 8.2.1001 IMSM drivers and you should be fine.

[BooksForumuser]

Well, I've had the best results latency-wise by turning off both the media bay and e-sata in the BIOS (A11). When either is enabled, my latency spikes significantly -- with the media bay its the iaStor.sys, and with the e-sata its USBPORT.sys (although this settles down after a while until its negligible). With both enabled, I'm consistantly in the 9,500 to 10,000 range, while with both disabled it's in the 300-600 range with an occasional spike to 1,000.

My vote goes to the media bay and the Intel Matrix Storage Manager (8.7 -- I haven't tried a downgrade to 8.2 yet).

[Circus_boi]

Originally Posted by MiB

Just revert back to the Intel 8.2.1001 IMSM drivers and you should be fine.

Sorry for the n00b question,b ut how does one revert back to the prior version after an update? It would be great if that is the simple answer; who knows what good that update was anyway, after all! Thanks!

[Circus_boi]

Originally Posted by Circus_boi

Sorry for the n00b question,b ut how does one revert back to the prior version after an update? It would be great if that is the simple answer; who knows what good that update was anyway, after all! Thanks!

I should mention that in Device Manager > Storage Controllers > Intel(R) ICM8M-E/ICH9M-E STAT RAID Controller > Properties > Drivers, the "Rollback Driver" is NOT available [i.e. the button is there, but is not available to be clicked on]....?

[jpalo]

Originally Posted by Circus_boi

I should mention that in Device Manager > Storage Controllers > Intel(R) ICM8M-E/ICH9M-E STAT RAID Controller > Properties > Drivers, the "Rollback Driver" is NOT available [i.e. the button is there, but is not available to be clicked on]....?

Same here, when installing Vista the button was clickable for a while but eventually when I went and tried to roll back (as clean re-install didn't fix the issue), the rollback was grayed out. No worries, I uninstalled the driver with the Uninstall button and Vista took the original drivers into use. No latency issues with the version 6.9.1.1001.

Per Dell support suggestion, I was actually following the steps in "Dell Business Client E-Family Re-Image How-To Guide" exactly and Latency was nonexistent up until I had installed "Intel Storage - Intel Matrix Storage Manager" by updating the driver in Device Manager. Before that I had installed "Microsoft QFEs (System Utilities)", "Intel Mobile Chipset" and "PCMCIA / Smartcard controller" in that order, but IMSM was the culprit and nothing I installed after that remedied the Latency issue.

[MiB]

Originally Posted by Circus_boi

Sorry for the n00b question,b ut how does one revert back to the prior version after an update? It would be great if that is the simple answer; who knows what good that update was anyway, after all! Thanks!

Uninstall the 8.7 drivers in device manager, then execute the 8.2 drivers linked in my earlier post.

[Circus_boi]

Originally Posted by jpalo

Same here, when installing Vista the button was clickable for a while but eventually when I went and tried to roll back (as clean re-install didn't fix the issue), the rollback was grayed out. No worries, I uninstalled the driver with the Uninstall button and Vista took the original drivers into use. No latency issues with the version 6.9.1.1001.

Per Dell support suggestion, I was actually following the steps in "Dell Business Client E-Family Re-Image How-To Guide" exactly and Latency was nonexistent up until I had installed "Intel Storage - Intel Matrix Storage Manager" by updating the driver in Device Manager. Before that I had installed "Microsoft QFEs (System Utilities)", "Intel Mobile Chipset" and "PCMCIA / Smartcard controller" in that order, but IMSM was the culprit and nothing I installed after that remedied the Latency issue.

Thanks Jpalo. I did that and you are right, it reverts back to the original set that presumably came with the computer. I now have version 6.2.0.1019. The latency is much better, but still get red bars every 10 secs. or so. Prior to my update, when I had version 8.2.0, I believe, I get only green bars and everything was cool. Do you know how I can upgrade back to version 8.2.0? Going to the Intel and Dell support pages, they only let me upgrade to the newest 8.7.0 version, which as we all know, sucks on the latency front....

[UPDATE #1] Never mind, just saw MiB's post. Am downloading 8.2 now; keeping my fingers crossed....
[UPDATE #2] Sweet soothing green bars......thanks v. much for your help, Jpalo and MiB, + rep!! Now if only Intel will go ahead and fix whatever the issue is, since it's clearly their driver that's causing the latency problems....

Much appreciated!

[ziesemer]

Originally Posted by MiB

I've been saying for quite some time that the primary cause are the Intel drivers.

If you're willing try this to see if it might help;

Go to Start, type System Configuration and select it.

1. In the Services tab - uncheck Intel Matrix Storage Event Monitor

2. In the Startup tab - uncheck Raid even monitor

Restart the system and restest.

To restore things back to the way they were, go back and check on those 2 boxes again.

Agreed, it is the Intel drivers. Unfortunately, neither the Intel Matrix Storage Event Monitor service or startup item appear to affect the DPC latency results at all. The issue seems to be in the core driver - not the event monitoring service or startup item, which also seems to be confirmed by the results from xperf.

Originally Posted by MiB

Just revert back to the Intel 8.2.1001 IMSM drivers and you should be fine.

Originally Posted by Circus_boi

Thanks Jpalo. I did that and you are right, it reverts back to the original set that presumably came with the computer. I now have version 6.2.0.1019. The latency is much better, but still get red bars every 10 secs. or so.

I've found that operating without any version of the Intel driver seems to be best, at least in terms of DPC latencies. I had the same problem that downgrading helped, but still had the spikes every 10 seconds or so. Removing the Intel driver entirely and just using the default Microsoft driver keeps my DPC latencies consistently "in the green" (below 500µs).

Originally Posted by Circus_boi

Sorry for the n00b question,b ut how does one revert back to the prior version after an update? It would be great if that is the simple answer; who knows what good that update was anyway, after all! Thanks!

Originally Posted by Circus_boi

I should mention that in Device Manager > Storage Controllers > Intel(R) ICM8M-E/ICH9M-E STAT RAID Controller > Properties > Drivers, the "Rollback Driver" is NOT available [i.e. the button is there, but is not available to be clicked on]....?

Originally Posted by MiB

Uninstall the 8.7 drivers in device manager, then execute the 8.2 drivers linked in my earlier post.

Don't "roll back" - just uninstall completely. The Microsoft-provided driver should then take over. My device manager shows this as "Standard AHCI 1.0 Serial ATA Controller". Microsoft, 6/21/2006, 6.0.6001.22134. The driver details shows this as consisting of atapi.sys, ataport.sys, msahci.sys, and pciidex.sys.

I did find that this sometimes requires 2 reboots before everything is finalized and the MS AHCI driver actually takes over.