Linked by Thom Holwerda on Mon 27th Aug 2007 22:21 UTC
Windows A curious network performance reduction noticed by many Windows Vista users of the 2CPU forum that became the talk of Slashdot last week has been identified as having been caused not by DRM, as Slashdot users expected, but by a curious prioritization 'feature' of Vista that's intentionally biased toward Media Player at the expense of network and system resources.
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Here's How Awful Vista Really Is
by segedunum on Tue 28th Aug 2007 20:42 UTC
segedunum
Member since:
2005-07-06

I've always loved Mark Russinovitch's stuff, and used a lot of his tools, and was going to do a dissection of his blog post with the meaty bits in, but Rob Love has done better than me on what I was going to say:

http://blog.rlove.org/2007/08/those-dang-dpcs-clogging-mmcss.html

From Mark's blog:

http://blogs.technet.com/markrussinovich/archive/2007/08/27/1833290...

"Network DPC receive processing is among the most expensive, because it includes handing packets to the TCP/IP driver, which can result in lengthy computation. The TCP/IP driver verifies each packet, determines the packetís protocol, updates the connection state, finds the receiving application, and copies the received data into the applicationís buffers."

This is an entirely separate issue from the whole MMCSS debacle and people are viewing it the wrong way round. If you're doing networking, forget Vista period. Copying a file consumes 41% CPU time. Yes, you read that right. 41 $%£&+%$ percent! Disclaimer: I know he gets that from the task manager, but that's a significant chunk of CPU time absolutely nothing like that seen on XP or on other operating systems with a similar operation.

Networking is utter shite in Vista, basically. No other word for it. Read Rob's blog for more info. Now, we'll move on to the effect on MMCSS. That's right. It's not MMCSS causing this per se. MMCSS may make it worse depending on what it is doing.

Because of this appalling networking situation, naturally, something needless taking up about half of your CPU time is detrimental to multimedia performance - and that's all Microsoft concentrated on. So, this had to be fixed somehow. Rather than talking to each other, a terrible piece of bandaiding took place. Microsoft actually new about this, and specifically for MMCSS, they decided to give MMCSS the power to throttle the network! Can anyone say bugs and layering violation?

Yes, boys and girls. In Vista, MMCSS is given the power to throttle your network speed because Vista is so bloody crap at networking!

I mean, this is worse than I ever thought possible. Heaven help you if you use an application that uses the CPU quite intensely, and you want to use your network at the same time. God only knows what effect this might have on other processes, streaming video over the network or networked games. Forget Mark's explanation that Microsoft used magic numbers to thottle the network. It's the fact that they are needed at all to cover up a terribly shoddy system. It's absolutely insane.

Given the state of this, fun and games with Windows Server 2008's networking stack is going to be most interesting..........

Edited 2007-08-28 20:47

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