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When asking a customer to enable RSS in their data center to improve network performance (very high UDP packets-per-sec rate), I was told that they generally turn it off, because after various problems in the past, Microsoft and the hardware vendor (which I believe to be HP) would often ask them to turn off RSS, because it may destabilize things.

This tidbit, and the additional observation that although RSS was globally enabled by default in Windows 2008 (I verified this in 2008 R2), in 2012 (verified in 2012 R2) that has been changed to "disabled" by default, lead me to believe there might be some truth to the instability claim. But google doesn't seem to be my friend here. And on the TechNet pages on RSS improvements in Windows 2012, it seems RSS rocks (which my own tests on scaling UDP reception on a very high-spec Win2012R2 system confirmed) and is still the way to scale.

Does anyone here have good/bad experience with RSS and stability to share, or some pointer to problems with it?

Evgeniy Berezovsky
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  • I can vouch for it causing performance problems between server 2012 and older versions of windows or clients that aren't windows in the past. I'm not sure if this is still the case. – hookenz Oct 02 '15 at 00:40
  • @Matt What kind of performance problems? (RSS will of course incur some CPU overhead to manage the distribution queues - as a tradeoff to be able to use more than one core.) – Evgeniy Berezovsky Oct 02 '15 at 02:05
  • It was a very long time ago. Back in 2010, In fact, it was actually server 2008 not 2012 sorry. It didn't affect everyone. But mostly some older clients. It was the RDP protocol. I turned off RSS and the problem went away never to return. I noticed no difference for other clients. – hookenz Oct 02 '15 at 02:11
  • @Matt So the problem was slow / unresponsive RDP connections? – Evgeniy Berezovsky Oct 02 '15 at 02:13
  • yes is that what you were seeing? Interestingly the Linux world has RSS built in as well. And in rather old kernels. – hookenz Oct 02 '15 at 02:17
  • If you're interested read this: https://www.kernel.org/doc/Documentation/networking/scaling.txt I think the techniques are very similar or identical to windows. It explains what's happening very well. – hookenz Oct 02 '15 at 02:18
  • I'm not sure about the validity of this question on Serverfault, considering that we seem to really be discussing software bugs. They will be smoothed over in time. – Ryan Ries Oct 02 '15 at 02:26

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