Even if they have it configured correctly, you’re forced into constraining your adapters to using less processors. In practice, we’ve seen this provide very little value if any with SET teams. Note: I’ve seen folks try to avoid this by preventing a NIC from using the same processors used by other NICs (overlapping). This is what happened to your CIO, the queues for the file server hosting his/her user profile was on the same processors as another workload performing backups. If another workload (for example VM B) starts receiving more traffic and one of its queues are mapped to the same processor as a queue from VM A, one of them may suffer. One of the challenges with VMMQ in Windows Server 2016 (Static VMMQ) is that the indirection table – the assignment of a VMQ to be processed by a specific processor – cannot be updated once established. “ this would be about the best place in the entire world to work, if it weren’t for all these complainers…” ) The following day, you’ll be asked to root cause what happened and develop an action plan to ensure the CIO never has this experience again. Your CIO calls in the support team after-hours because of the terrible performance. I think we all know the story that’s about to unfold. Little did you know, your CIO is a night-owl and a few hours later begins working right as some backups begin on the file servers hosting the user profile. Note, the video is sped up to show the process occurring a bit quicker than normal.Īfter a hard day’s work, you head home for the day. Here’s a video showing the Dynamic Coalescing. The system has coalesced or packed all the queues onto one CPU core as was necessary to sustain the workload. Only one CPU core (the green bar) is processing packets destined for a virtual NIC. You can see we’re using the performance counter Hyper-V Virtual Switch Processor > Packets from External/sec and there is one bar for each CPU core engaged. The picture below shows a virtual NIC receiving a low amount of network traffic. Queue packing is more optimal for the host as the system would otherwise need to manage the distribution of packets across more CPUs the more CPUs are engaged, the more the system must work to ensure all packets are properly handled. When network throughput is low, Dynamic VMMQ enables the system to coalesce traffic received on a virtual NIC to as few CPUs as possible we call this queue packing because we’re packing the queues onto as few CPU cores as is necessary to sustain the workload. I’m starting to think those midnight network slow-downs may be a thing of the past! Automatic tuning of the indirection table (so the VM can meet and maintain the desired throughput). ![]() Now in Windows Server 2019 we can dynamically remap VMMQ’s placement of packets onto different processors. However, in part due to the rearchitected design in Windows Server 2016 to bring VMMQ, Dynamic VMQ was not available in Windows Server 2016. Originally, we enabled the dynamic updating of the indirection table, called Dynamic VMQ, in Windows Server 2012 R2. While the indirection table is always established by the OS, we can offload the packet distribution to the NIC when offloaded to the NIC, we call this VMMQ. The distribution of these packets to separate processors can be done in the OS, or offloaded to the NIC. Synthetic Accelerations in a Nutshell – Windows Server 2016Īs a quick refresher, Virtual Receive Side Scaling (on the host) creates an indirection table which enables packets to be processed by multiple, separate processors. ![]() Synthetic Accelerations in a Nutshell – Windows Server 2012 R2.Synthetic Accelerations in a Nutshell – Windows Server 2012.Microsoft recommends using Switch Embedded Teaming (SET) as the default teaming mechanism whenever possible, particularly when using Hyper-V.īefore we get to the good stuff, here are the pointers to the previous blogs: Public Service Announcement: Most of what you see below will not apply if you’re using an LBFO team. This may come in the form of reducing CPU processing for network traffic and/or ensuring a smooth and consistent experience for the virtual machines on your host which ultimately means happy tenants running more virtual machines (and no midnight calls to troubleshoot the all-to-common “network slow-down” ![]() The multi-release journey is designed to achieve one primary goal improving your (and your tenant’s) networking experience in the Software Defined Data Center. In Server 2019, we took learnings and expanded on the work that began in Server 2012 R2 with Dynamic VMQ and Server 2016 with VMMQ, to bring Dynamic VMMQ (d.VMMQ). Dan Cuomo here for our final installment in this blog series on synthetic accelerations covering Windows Server 2019.
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