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If your Internet speed is slower than it's supposed to be...

D

Deadtrees

Platinum Member
I was reading a post in this forum and someone there was complaning how AERO slows down his internet speed. I thought it was a ridiculous claim until the other person pointed out how MMCSS(Multimedia Class Scheduler Service) 'can' cause such a problem.
Simply put, MMCSS controls all the services that depend on schost.exe. Network depends on svchost. When multimedia services start, MMCSS 'can' decrease of network performances. In some cases, the network speed goes down even there's a music playing on a web-browser.

To see whether your computer is effected by it; 1. open up your task manager, 2. start downloading big chunk of files, 3. run multimedia programs like Media player, 4. check to see whether there's a drop in network speed.

To make it better, check the links below. There's a way of turning off this feature but it is not recommanded as it can cause irregular performance decrease. In my case, I just changed the value form 10 to 70.

http://support.microsoft.com/kb/948066/en-us
http://msdn.microsoft.com/en-u...684247%28VS.85%29.aspx


EDIT: My bad....I though I posted it on Networking Forum. Mod, can you move this thread to Networking forum? Thanks!

Punting to the network forum. Someone better be there to catch this!

-ViRGE
 
I checked and saw that MMCSS is currently running on my computer. I do have Foobar open, so that's probably using the service. I usually have iTunes or Foobar open with the browser and I never had a drop in speed. I'm a frequent downloader and it rarely affects the speed. I watch movies while downloading and see no difference in speed either. I say this because isn't MMCSS running when these multimedia programs are active?

* Audio
* Capture
* Distribution
* Games
* Playback
* Pro Audio
* Window Manager

Did the registry value edit change anything for you?
 
Originally posted by: boorns
I checked and saw that MMCSS is currently running on my computer. I do have Foobar open, so that's probably using the service. I usually have iTunes or Foobar open with the browser and I never had a drop in speed. I'm a frequent downloader and it rarely affects the speed. I watch movies while downloading and see no difference in speed either. I say this because isn't MMCSS running when these multimedia programs are active?

* Audio
* Capture
* Distribution
* Games
* Playback
* Pro Audio
* Window Manager

Did the registry value edit change anything for you?
Click to expand...

Here's a spec. of the person's computer: 10mb Internet connection, Core2Duo 6400, 2GB RAM, 320GB Raid HDD, 8600GT GPU. He said changing GPU to Radeon 4670 fixed the problem; however 2D GPU perfomance took a hit: changing windows size as well as dragging windows were laggy.
He changed GPU back to 8600GT and upon disabled Windows transparency, network performance improved. Also, overclocking CPU to 2.6Ghz (2.13 being the original speed) increased network performance to 40%.

It seems like this problem varies from systems to systems. In my case, this problem does not affect me and my system is Q6600 @ 3.2 Ghz, 8600GT 256MB with 6 10mb internet connection. I haven't checked to see if it affects my internal network speed but as it's only 10mb home network, I didn't bother to check it. Anyway, I changed registery value to 70 (the max. value) to be safe.
 
Is the person testing the actual connection speed of the Internet or the connection spikes in Task Manager?

"however 2D GPU perfomance took a hit: changing windows size as well as dragging windows were laggy."

It's weird that a service that controls basically media applications affects the resizing of a window, which is not related to the internet speed. I don't know enough to explain the 2D part.

I don't understand how MMCSS involves Aero though (possibly as Window Manager?). I could see how starting or loading things in a browser might be slower with Aero, but the internet speed should be the same regardless of Aero/transparency. Maybe the CPU OC boosted the speed of opening the browser? I don't know the exact complaint though, so I'm guessing here.

http://blogs.zdnet.com/Ou/?p=711
MMCSS did affect at 120mbps, at Gigabit speeds.

http://www.ghacks.net/2007/08/...r-while-playing-music/
Transfers though, not Internet.

http://blogs.technet.com/markr...007/08/27/1833290.aspx
More information, but the only effect seems to be on transfers and connections over 100mbps.

Strange issue. I don't think there's any need to change the registry value from 10 to 70. The problem with this really is about file transfer speeds.
 
Transfers via FTP. Files are DVD ISOs.

With Itunes playing in the background on PC2 and no media running on PC1:

PC1 --> PC2 = 12-15MB/s
PC2 --> PC1 = 22-30MB/s

With Itunes off, and no other media running on either PC:

PC1 --> PC2 = >70MB/s
PC2 --> PC1 = ~65MB/s

In this latter scenario, HDD speed is the bottleneck.

Connected by an 8-port Procurve Giga switch, no Jumbo frames. Both PCs are C2D-based with onboard PCIe NICs. Vista X64 on both.


Edit: Aero is enabled on both PCs at all times, and does not seem to make a difference in transfer speeds. There might be a moderate dip in speeds when a 3D Aero effect (i.e. flip) is being used.
 
MMCSS was implemented so that multimedia, games, would be set to a higher priority for resources than other task. That includes giving it higher cpu priority, memory, storage, gpu, network. It effects things across the board. The problem is how windows identifies those applications. It sees anything that plays a sound as being multimedia and needing priority. Bad idea. They should have made it where the user can specify what is or is not in need of a priority boost.

You can disable it in services. I do it on OS install.
It says windows audio is dependent on the service, but sound still works fine.


 
Multimedia class scheduler is one of the worst ideas to come out of MS in quite some time.

It's a gross hack/workaround, for what is really a device-driver problem.

Apparently, MS found that (some, not all) network device drivers seemed to take up a high percentage of CPU time in the kernel mode (high interrupt load, most likely), that caused multimedia apps to lag and have audio breakup, etc.

So as a workaround to that, instead of relying on the highly-refined NT scheduler, MS added this hack that throttles network speeds (resulting in lower interrupt load), whenever some audio app is playing.
 
Originally posted by: boorns
Is the person testing the actual connection speed of the Internet or the connection spikes in Task Manager?

"however 2D GPU perfomance took a hit: changing windows size as well as dragging windows were laggy."

It's weird that a service that controls basically media applications affects the resizing of a window, which is not related to the internet speed. I don't know enough to explain the 2D part.

I don't understand how MMCSS involves Aero though (possibly as Window Manager?). I could see how starting or loading things in a browser might be slower with Aero, but the internet speed should be the same regardless of Aero/transparency. Maybe the CPU OC boosted the speed of opening the browser? I don't know the exact complaint though, so I'm guessing here.

http://blogs.zdnet.com/Ou/?p=711
MMCSS did affect at 120mbps, at Gigabit speeds.

http://www.ghacks.net/2007/08/...r-while-playing-music/
Transfers though, not Internet.

http://blogs.technet.com/markr...007/08/27/1833290.aspx
More information, but the only effect seems to be on transfers and connections over 100mbps.

Strange issue. I don't think there's any need to change the registry value from 10 to 70. The problem with this really is about file transfer speeds.
Click to expand...

It wasn't about the brower loading speed or speed of opening a brower. It was about network speed, internet speed being part of one.

I ,too, don't understand why stuffs like AERO, Windows Transparency would affect the network speed. I mean, I do understand how andy why MMCSS slows down network speed but the whole thing seems silly. I guess, because 2D really isn't 2D on Windows Vista and 7, it is treadted as multimedia content thus network speed goes down.

BTW, when MMCSS detects multimedia, network throughoutput is limited to 10 packets per 10ms. Check the chart in the link below.
There you can see how this 10 packets per 10ms limits network speed. Keep it mind that the yellow coloured part of the chart is Vista's default 10 packets per 10 ms and the green part is 70 packets per 10ms limit. The difference it makes is just huge! A network copy went down 27 MB/s to 4MB/s when a MP3 file was being played.

http://translate.google.com/tr...&tl=en&history_state0=

What can I say? This is just silly.

 
Originally posted by: Deadtrees
Originally posted by: boorns
Is the person testing the actual connection speed of the Internet or the connection spikes in Task Manager?

"however 2D GPU perfomance took a hit: changing windows size as well as dragging windows were laggy."

It's weird that a service that controls basically media applications affects the resizing of a window, which is not related to the internet speed. I don't know enough to explain the 2D part.

I don't understand how MMCSS involves Aero though (possibly as Window Manager?). I could see how starting or loading things in a browser might be slower with Aero, but the internet speed should be the same regardless of Aero/transparency. Maybe the CPU OC boosted the speed of opening the browser? I don't know the exact complaint though, so I'm guessing here.

http://blogs.zdnet.com/Ou/?p=711
MMCSS did affect at 120mbps, at Gigabit speeds.

http://www.ghacks.net/2007/08/...r-while-playing-music/
Transfers though, not Internet.

http://blogs.technet.com/markr...007/08/27/1833290.aspx
More information, but the only effect seems to be on transfers and connections over 100mbps.

Strange issue. I don't think there's any need to change the registry value from 10 to 70. The problem with this really is about file transfer speeds.
Click to expand...

It wasn't about the brower loading speed or speed of opening a brower. It was about network speed, internet speed being part of one.

I ,too, don't understand why stuffs like AERO, Windows Transparency would affect the network speed. I mean, I do understand how andy why MMCSS slows down network speed but the whole thing seems silly. I guess, because 2D really isn't 2D on Windows Vista and 7, it is treadted as multimedia content thus network speed goes down.

BTW, when MMCSS detects multimedia, network throughoutput is limited to 10 packets per 10ms. Check the chart in the link below.
There you can see how this 10 packets per 10ms limits network speed. Keep it mind that the yellow coloured part of the chart is Vista's default 10 packets per 10 ms and the green part is 70 packets per 10ms limit. The difference it makes is just huge! A network copy went down 27 MB/s to 4MB/s when a MP3 file was being played.

http://translate.google.com/tr...&tl=en&history_state0=

What can I say? This is just silly.
Click to expand...

I see what you mean now. I didn't consider network file sharing at first. Only thought of it as download/upload speed.
 
In general the retail version of Windows is tuned toward the average none business user.

However has in a Huge variety of settings. The idea is that IT people that install them for specific business would be able to tune it according the client?s needs.

A computer used all day by a typist who does only word processing can be set differently to one that a computer that is used mainly by game developer, or medical technician.

The problem is that many enthusiasts do not really understand what those setting can do and how to use but instead they are guided by Myths disinformation wishful thinking and the like.

At home, I have few needs that are diverse in nature so I use few computers tuned according to specific needs.
As an example, my server does not need fancy video and thus does not even capable to do fancy video.
 
I'm on a gigabit network and my transfers remain constant regardless of audio playing.

Win 7 RC 35MB/s (via FTP) with and without audio (slow laptop hdd).

Mills
 
Originally posted by: Modelworks
You can disable it in services. I do it on OS install.
It says windows audio is dependent on the service, but sound still works fine.
Click to expand...

Not in Windows 7. Windows Audio is stopped automatically, and will not restart if MMCSS is stopped.
 
Originally posted by: Raduque
Originally posted by: Modelworks
You can disable it in services. I do it on OS install.
It says windows audio is dependent on the service, but sound still works fine.
Click to expand...

Not in Windows 7. Windows Audio is stopped automatically, and will not restart if MMCSS is stopped.
Click to expand...

Yeah win7 requires a different approach.

Edit the registry like below to disable the feature
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
Change NetworkThrottlingIndex to FFFFFF


You can read all the other settings here:
http://msdn.microsoft.com/en-u...684247%28VS.85%29.aspx
 
Originally posted by: dawza
Transfers via FTP. Files are DVD ISOs.

With Itunes playing in the background on PC2 and no media running on PC1:

PC1 --> PC2 = 12-15MB/s
PC2 --> PC1 = 22-30MB/s

With Itunes off, and no other media running on either PC:

PC1 --> PC2 = >70MB/s
PC2 --> PC1 = ~65MB/s

In this latter scenario, HDD speed is the bottleneck.

Connected by an 8-port Procurve Giga switch, no Jumbo frames. Both PCs are C2D-based with onboard PCIe NICs. Vista X64 on both.
Click to expand...

Makes me want to puke.
 
Originally posted by: JackMDS
In general the retail version of Windows is tuned toward the average none business user.

However has in a Huge variety of settings. The idea is that IT people that install them for specific business would be able to tune it according the client?s needs.

A computer used all day by a typist who does only word processing can be set differently to one that a computer that is used mainly by game developer, or medical technician.

The problem is that many enthusiasts do not really understand what those setting can do and how to use but instead they are guided by Myths disinformation wishful thinking and the like.

At home, I have few needs that are diverse in nature so I use few computers tuned according to specific needs.
As an example, my server does not need fancy video and thus does not even capable to do fancy video.
Click to expand...

Alright fine. Personally I run a Win 7 with all non-core services running. It's primary purpose is as a NAS + a few server apps. It can be done, but it's still like guessing the dark for the most part and not as efficient as it could be.

When MS provides a simple installation customization tool, where you can right from the outset install Windows with certain features not available or services started/not started then it would be a valid point.

MS evens goes to the extent of stating that you audio may not work if you disable the service. It's right there in the description. Not even a clue that you are better off disabling that service if you actually use the machine for something more than watching videos or playing music which I think is pretty much all of us.
 
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