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long duration Deferred Procedure Calls (DPC)

DPC deferred procedure calls

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#1 benfrank

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Posted 26 February 2013 - 08:56 AM

FYI, I use PowerSDR, a Software Defined Radio application that is used to operate a Flex 5000A amateur transceiver. This application uses real-time digital signal processing and needs to operate in a Windows environment with reasonably low duration Deferred Procedure Calls (DPC). The application is somewhat similar to digital audio processing products.

Using a DPC checking tool while running PowerSDR and several other applications, including Norton Internet Security, I have discovered that Malwarebytes Pro causes long duration DPC's about every 15 to 30 seconds on the order of 6,000 to 18,000 microseconds of latency. DPC's of this duration can cause dropouts of the data stream. With Malwarebytes disabled the maximum DPC is less than 400 microseconds over several minutes of testing.

While I have solved this problem by disabling Malwarebytes when the PowerSDR application is in use, this is a less than ideal work-around becasue I also use a web browser while opearting the transceiver. So for what it is worth, this charateristic is undesirable in situations where digitial signal processing applications are running. Your developers might want to take a look at the code to see if it could be made less demanding of system resources.

My PC is a Dell 9000 with i7-920 processor, 8GB RAM, and Windows 7 with latest updates.

#2 AdvancedSetup

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Posted 26 February 2013 - 02:36 PM

Thank you for the feedback Ben however your needs of using a Windows computer for controlled digital signal level is beyond the scope of "normal". We are certainly always looking for ways to improve performance but due to the technology used for file and website monitoring we will always be consuming IO at rates that will affect your audio application.

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#3 benfrank

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Posted 26 February 2013 - 06:13 PM

Thank you for your response to my comments. I appreciate that Malwarebytes cannot cover all operating conditions, although applications that employ digital signal processing (audio or video) are not a uncommon. FWIW, I offer the observation because it may benefit other users who encounter similar issues and they may not necessarily be aware that Malwarebytes can cause long duration DPCs.

Malwarebytes has been an excellent complement to Norton Internet Security on my PC and I will continue to use it when not running DSP applications.

#4 orientfan

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Posted 27 February 2013 - 06:22 AM

DPC Latency issues have been reported before. I posted a message as a follow up to someone else reporting this but neither of us received a reply from Malwarebytes. Turning off Website Blocking fixes the issue for me but that's not a solution.

It's also been reported on Wilders Security forum - http://www.wildersse...ghlight=latency

I wish they could fix this.

#5 Insomniac

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Posted 27 February 2013 - 11:05 AM

Hey all, it's been a while since I've frequented these forums.

I've been having a strange issue recently (last few weeks?), and I finally traced down the problem... and MBAM is the culprit!

Basically, I'm usually listening to music while on my laptop, and lately I've been noticing a very annoying, intermittent crackling sound in my music. I suspected my music player first, but noticed the same issue with different media players, different files and even with the audio from Youtube. It even happens sometimes when Windows is playing one of its own sounds.

I tried restoring back to a known good system image, and the problem disappeared... Got all my security stuff updated, and the issue returned!

After fiddling around a bit, I've found a way to reproduce the issue. It seems to be related to network traffic. For example, I can reproduce the issue 100% reliably by pulling out the ethernet cable from my laptop, and re-inserting it while music is playing. After a second or two, there will be major crackling and distortion to the audio for a few seconds.

If I disable Malwarebyte's Website Blocking feature (paid version, obviously), the issue disappears. I can plug the ethernet in and out without any effect to the audio.

Note that this crackling happens when MBAM is NOT blocking an ip address. I've never had any reason to believe that this system has ever been infected, so I highly doubt malware is the cause.

I have had Website blocking enabled for about a year or so now, and only noticed this issue within the last few weeks... and this issue was present after restoring my system to an image from four months ago, as soon as MBAM had updated. So it must have been introduced within the last couple of updates.


My laptop's an Asus N55SF, running Win 7 64. (4GB RAM, i7 2630QM, GT555M). I use MSE as my AV solution, Win 7 firewall control, and MBAM running realtime. Very little else I leave running in the background.


I'd be interested if anyone else can reproduce this issue... Get some nice, clear music playing, make sure Website Blocking is enabled, and then pull out and re-insert your ethernet cord and listen for a crackling noise. This has been driving me nuts!

#6 AdvancedSetup

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Posted 27 February 2013 - 03:28 PM

Yes we understand and as I said we are always looking for new ways to improve our program and if we're able to we certainly will but you also have to realize that it's often not possible to support 100% of the billion plus computers out there and the millions of various programs they may have.

Thank you again for your input.

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#7 AdvancedSetup

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Posted 27 February 2013 - 03:37 PM

If you were using special audio software or some types of digital music applications you might experience this issue as reported here

However I would not expect the average user to experience this and we're not really having any obvious multiple postings about this issue so you might want to post in the PC Help forum and have someone work with you to test some things out to see what might be going on. None of my own personal systems or systems at work are experiencing this issue.

Thanks

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#8 Insomniac

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Posted 27 February 2013 - 07:20 PM

I'm not using anything that the average user wouldn't be... I'm playing my music library via MediaMonkey from the computer's local drive (no media sharing or anything like that). I've disabled all of Asus' audio bloatware, all I'm using is the standard (up to date) Realtek audio driver. Speakers driven from headphone out (though this also happens with the internal speakers). The audio source is irrelevant however, the problem occurs with any audio playback, from any of my media players.


I get the feeling that if anyone else is having this issue, they either may not have noticed it, or not tracked it down to MBAM. It's the last thing I expected to cause it, and it was difficult to diagnose due to how intermittent the problem is. I was only able to figure out the cause when I realised that the action of plugging the ethernet cable in would cause it to happen reliably.


This problem is quite subtle and not severe enough to be noticable unless you listen to a lot of music on your computer. The audio might only crackle for a split second once every couple of songs. This never happened with past versions of MBAM, so I'm not sure why one of the recent updates is causing it. (I know it's not a change I've made to my system, because the issue re-occured after imaging my system back to a time at which the issue did not exist, as soon as I updated MBAM).





I might test this on a few other systems if I get the chance, and if it is only me I guess I'll have to figure out a way to avoid it.

#9 AdvancedSetup

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Posted 27 February 2013 - 08:43 PM

Well if you do want help looking into it further let us know. I do know that SoundBlaster has a known issue with crackling on new cards and nothing to do with any specific hardware / software combinations that can be found as the issue actually even happens and you can hear it while in a BIOS screen.

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#10 Insomniac

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Posted 27 February 2013 - 09:20 PM

Well, I'd definitely like to have a shot at solving the problem.

I can make a youtube video demonstrating the problem, if you'd like. It is not related to soundblaster, I'm using realtek onboard audio.

If I untick MBAM's website blocking, the problem vanishes completely. Re-enable and the problem returns. I can demonstrate this if you want to see it yourself. I've tested it 10-20 times and it's completely reproducable and related to Malwarebytes. The older versions of MBAM did not cause this.

#11 boombastik

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Posted 27 February 2013 - 09:27 PM

I have the same problem with realtek and asus. They use same irqs with sound and lan, so when u have malwarebytes ip protection which makes dpc latency bigger u take crackling noises.
Also few times fileshield also has flows. Make a test: go start up a music file in windows media player with only file shield enabled then go and open skype then u take craclink music noises, now try the same again without any shield you dont take cracklink noises.
Also with file shield anabled movies on k lite when u start it u take shuttering video u must closed the k lite and the reopen it.( somthing has to do with the new zero day heurestic)

#12 Crumbs

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Posted 28 February 2013 - 06:56 AM

I have the same problem as well. I have a asus n55sl. When website blocking is turned on audio starts stuttering, and it goes away when I turn it off.

#13 stringbob

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Posted 28 February 2013 - 11:37 AM

Ditto here. However, I'm using a Focusrite Saffire Pro 24 Firewire audio processor. I also tried a Line 6 USB Audio processor with the same results. Tried adjusting the latency buffer but that did no good. Something I haven't seen mentioned is:

+ audio dropouts every 10 or 15 seconds. The firewire connection light goes out during the dropout for 1 to 2 seconds.
+ A severe audio distortion occurs, mostly on Youtube videos. This is not the typical clicking and popping, but a totally garbled, unintelligable mess. It isn't 100% like the clicking, and there's seemingly no event that starts it. It just happens..

Like everyone else, after exhaustive testing, the only culprit I found was Malwarebytes, specifically the live website blocking.

#14 Insomniac

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Posted 28 February 2013 - 04:39 PM

Glad I'm not going crazy. Stringbob, are you also on an Asus laptop?

#15 exile360

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Posted 28 February 2013 - 05:13 PM

Thanks for all of the valuable info guys. This particular issue has been plaguing us for a long time and we've never reproduced it. It appears to be hardware specific, which explains why it's not often reported. When the sound driver shares IRQ space with LAN, anything sitting on the LAN could potentially cause latency with audio, so for us that means our website blocking mechanism.

I do not know if this is a problem we can solve, but I do have the developers investigating it to see if we can find a solution as performance of the protection module is one of our areas of focus for our upcoming releases.
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#16 Insomniac

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Posted 28 February 2013 - 07:16 PM

@Exile,

Thanks for the reply. As to whether you can fix it or not, I can assure you that this problem was either not present on my machine, or was so rare as to be unnoticeable for the entirety of last year (with website blocking on). So it doesn't seem far-fetched that this is fixable (of course, I don't know the nitty-gritty of why it may or may not be possible).

One of the most recent program updates is what has made it a noticeable issue. I've confirmed this by using an old system image with an older version of MBAM, testing it, and then updating MBAM. Something about the new update is causing enough latency to stutter, whereas the old implementation didn't cause problems on my machine.



EDIT: Also, given that I can easily reproduce this problem, I'm happy to perform any diagnostic tasks to help you get to the bottom of this, provided they're no too time-consuming or invasive.

#17 exile360

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Posted 28 February 2013 - 07:59 PM

@Exile,

Thanks for the reply. As to whether you can fix it or not, I can assure you that this problem was either not present on my machine, or was so rare as to be unnoticeable for the entirety of last year (with website blocking on). So it doesn't seem far-fetched that this is fixable (of course, I don't know the nitty-gritty of why it may or may not be possible).

One of the most recent program updates is what has made it a noticeable issue. I've confirmed this by using an old system image with an older version of MBAM, testing it, and then updating MBAM. Something about the new update is causing enough latency to stutter, whereas the old implementation didn't cause problems on my machine.



EDIT: Also, given that I can easily reproduce this problem, I'm happy to perform any diagnostic tasks to help you get to the bottom of this, provided they're no too time-consuming or invasive.

Interesting, I don't recall any changes in the last release of MBAM to website blocking. The last major change I can recall happened in version 1.46, which was a pretty major overhaul to how it works (which actually improved performance for most on Vista/7 and 8).

Do you happen to have info on which version of Malwarebytes Anti-Malware this started with? That would help us to isolate the area of the code where the problem might be.
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#18 jdlk

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Posted 28 February 2013 - 09:00 PM

Yes we understand and as I said we are always looking for new ways to improve our program and if we're able to we certainly will but you also have to realize that it's often not possible to support 100% of the billion plus computers out there and the millions of various programs they may have.


After putting up with a long-term problem of stuttering sound when playing streamed audio, I finally got around to investigating the problem tonight.

I noticed excessive DPC latency, and after a couple of hours fruitlessly disabling a bunch of drivers, I had a hunch and disabled Malwarebytes. DPC latency problem gone instantly. A quick Google lead me to this thread.

As someone mentioned above, you can get around the problem by disabling malicious web site blocking, but that's hardly a solution.

I joined the forums to take issue with the support response. Listening to streaming audio is not a marginal activity, and many people do it all the time when they're on their PCs (e.g. listening to internet radio stations).

If you really can't solve this problem, then there should be a notice on your purchase page warning people that Malwarebytes can interfere with streaming audio or other real-time data streaming programs.

My PC is a relatively modern Win7x64 machine.

#19 AdvancedSetup

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Posted 28 February 2013 - 09:08 PM

I've merged the two topics as they appear to be the same overall concern.

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#20 Insomniac

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Posted 28 February 2013 - 09:59 PM

Are there download sources for the older versions of MBAM? I'm happy to install the last few in sequence and isolate which version it is.





Also tagged with one or more of these keywords: DPC, deferred procedure calls

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