Networking Division
Technical Advisory
TA-201
2111 N.E. 25th Avenue
Hillsboro, OR 97124-5961
Tuning Windows Server® 2008 R2 with Intel®
Ethernet 1 GbE/10 GbE/40 GbE Controllers Drops
Link Under Heavy Network Load
Products Affected
All 1 GbE, 10 GbE, and 40 GbE Intel network adapters running Windows Server® 2008 R2.
Problem Description
In some situations when Windows Server® 2008 R2 is under consistent high stress (both CPU and
network use), the NDIS driver might force a reset on the network, which might cause a link drop
and a reconnect.
Implications
Repeated link drop due to NDIS driver network resets.
Corrective Action/Resolution
For all corrective actions, make one change at a time and include an
incremental backup and/or restore points.
1. Before proceeding with any changes, create a restore point or make sure all relevant files are
backed up.
2. Review the error logs in the event viewer. Make changes to avoid any errors. Corresponding
services could be disable or delay the restart. For example, if there are Windows Error
Reporting (WER), change its service to restart after 10 minutes or longer. Since the system is
already under heavy load, repeated event logging increases CPU cycles. Do not change critical
services. For more information go to:
http://msdn.microsoft.com/en-us/library/windows/desktop/bb513641(v=vs.85).aspx.
3. Use perfmon and observe DPC queued/sec, rate, interrupts/sec on each core (<All instance>).
View it in a report format and not histogram or line (these are less meaningful formats).
4. In perfmon, add % C state time. Analyze this data and if possible turn off C states. Note
that the BIOS might provide options to change C states.
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May 2015
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TA-201
5. For each Intel 1 GbE, 10 GbE, or 40 GbE Ethernet adapter, change the registry value
*RSSProfile to four. For each port spread, change the RSS base processor number by setting
the registry value of *RssBaseProcNumber to different values. For example, one for the first
port, three for the second port, etc. Avoid setting this value to zero. Instead, change the
settings to reduce the load on core zero. Note that these two settings need to be done
manually in the registry. For more details, go to:
http://msdn.microsoft.com/en-us/library/windows/hardware/ff570864(v=vs.85).aspx
6. For each Intel 1 GbE/10 GbE/40 GbE adapter, turn off interrupt moderation. Go to the
Properties page and turn off interrupt moderation in both the Advanced and
Performance Options tabs.
7. Change the maximum number of RSS processors. Set the RSS processor for each network
adapter to two and observe the performance as to how each of the core DPCs are queued.
Depending on performance, try changing the RSS processors a value of four. Select a value
with a DPC load that gets spread across other cores and minimizes the load on core zero.
8. Set RSS queues to two queues on each network adapter/port. Again use perfmon to see how
DPCs are getting queued and spread the load on different cores leaving core zero with the least
number of DPCs or interrupts.
9. For each network adapter/port, set the preferred Numa Node (registry name *NumaNodeId) to
match *RssBaseProcNumber. To reduce the number of DPCs or interrupts in core zero, you
can select a different node.
10. If the problem continues after preforming the previous tuning instructions:
Upgrade the operating system to Windows Server® 2012 R2.
OR
Upgrade to a virtualized solution using a non-W2K8R2 host operating system and W2K8R2 as
a guest operating system.
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May 2015