Vnuma。 vNUMA: What it is and why it matters

To NUMA or not to NUMA

Vnuma

Instead of diving into and wasting much time on figuring out this anomaly, my recommendation is to remove the setting numa. numactl shows single vNUMA but I feel it could be 2 pNUMA nodes. If your solution requires both memory capacity and optimal memory performance then the memory RANKING CONFIGURATION is going to be very important in your server config. With remote hands options, your admins can delegate routine. The CPU view of the task managers shows the following configuration: The NUMA node view is selected and at the bottom right of the screen, it shows that virtual machine contains 8 sockets and 16 virtual CPUs. Lines show the ratio of non-local to local memory access. This feature can be enabled for smaller virtual machines, however, while still allowing ESXi to automatically manage the vNUMA topology. If changes have been made to these settings or the virtual machine has been moved to host with a different physical NUMA topology, you can restore the default virtual NUMA topology by clicking Use Hardware Topology on the NUMA Configuration page in the settings of a virtual machine. Covering this topic with them was very important because their legacy compute hardware contained dual socket 12-core CPUs whereas the new hardware utilized dual socket 10-core CPUs. - Virtual machines with Dynamic Memory enabled cannot use more processors or memory than available in a single physical NUMA node. A hypervisor runs on each node of the cluster and manages the physical resources. vCPU count exceeds the physical core count of the NUMA node. One thing that did occur to me and that is the Cluster On Die feature available on some processors. Now there is two questions: Is there any relation between virtual sockets and NUMA nodes? What I do see is if you deploy a VM with more virtual sockets than the of NUMA nodes in the host, vNUMA does some math and divides up the virtual sockets to an optimal and presents it. If you create a virtual machine with 192GB RAM and 1 Socket x 8 Cores per Socket, vSphere will still only create a single vNUMA node even though the requirements of the virtual machine will cross 2 pNUMA nodes resulting in remote memory access. As the graphs show, vNUMA scalability is at least as good as TreadMarks on all benchmarks, and significantly better on Barnes, Water, TSP and IS. According to the Itanium architecture, the correct result is either 5 or 6, depending on which operation appears first in the total order. The VM will end up having to access memory from the 2nd NUMA node which is remotely accessed since we are borrowing it from our neighbor NUMA node. For example, assume that a 4-byte integer variable has an initial value of 0. NUMA topology in Hyper-V virtual machines When a virtual machine is started, Hyper-V attempts to allocate all the memory for that virtual machine from a single physical NUMA node, if sufficient memory is available. Uniform memory access UMA is a shared memory architecture used in parallel computers. These guys break it down for you and make it very easy to understand. Each node generally applies any write updates that apply to pages that it has read copies of, and discards any irrelevant updates. The lefthand side of the diagram shows that the performance of the benchmarks within the SPEC OMP suite when using vNUMA is generally close to that of native performance for VMs having from four to 64 vCPUs. While this is prohibitively expensive for user-level DSM systems, the overhead can be kept much smaller in a thin hypervisor such as vNUMA. What would happen if a VM would be larger than one pNUMA node and the Xeon is not the M Version. A pair of adjacent CCXs shares access to two channels of physical DRAM 32 GB of DRAM in HB-series servers. Virtual NUMA, requires virtual hardware version 8 or later, can in some cases provide significant performance benefits for wide virtual machines that is, virtual machines with more vCPUs than the number of cores in each physical NUMA node , though the benefits depend heavily on the level of NUMA optimization in the guest operating system and applications. If you create a virtual machine with 192GB RAM and 1 Socket x 10 Cores per Socket, vSphere will still only create a single vNUMA node even though the requirements of the virtual machine will cross 2 pNUMA nodes resulting in remote memory access. vNUMA uses the concept of NUMA node-local memory to ensure that the guest will favour locally-managed memory when making allocation decisions, and as such works best with a NUMA-aware guest OS. All the processors in the UMA model share the physical memory uniformly. But opting out of some of these cookies may have an effect on your browsing experience. Each socket is listed and with each logical processor a cache map is displayed. Timeouts and sequence numbers, combined with a knowledge that the number of messages in-flight is bounded, are used to deal with occasional packet loss. 5 is no longer controlled by the Cores per Socket value. An improved algorithm might be one similar to the efficient distributed write protocol EDWP [], which tracks both read and write accesses, and prevents a transition to exclusive mode if more than one processor is accessing the page. Dig Deeper on VMware performance enhancements• For example: prior to vSphere v6. Certainly this design choice would limit scalability, but vNUMA is designed for optimal performance on a small cluster. The operating system considers the memory addresses from the other CPU pairs to be remote. Coreinfo shows the 16 vCPUs distributed symmetrically across two NUMA nodes and two sockets. This is similar in principle to benchmarks like TPC-C, but utilizes a smaller number of tables and a simpler mix of transactions. vNUMA is exposed once the vCPU count exceeds the physical core count of a single socket NUMA node. If you are using VMs with a non-default Cores per Socket setting and planning to upgrade to ESXi 6. While for normal DSM systems the concept of the manager node is a complication required for efficiency, for the virtual NUMA system it is actually a good match. Accessing to remote memory is very slower than local memory. These include distributed shared memory DSM libraries such as Ivy[] or Treadmarks[], which provide a limited illusion of shared memory to applications, provided that the programmer uses the primitives supplied by the library. There could be other workloads profiles where a non-wide VM performs much better than a wide VM. As an additional optimisation, the write queue is eagerly flushed at the time that a write is intercepted, if a release has been seen either on that instruction or in the previous interval and if the network card transmit queue is empty. In this example, the 16 vCPUs can be distributed across 2 NUMA nodes, thus 2 PPDs and VPDs are created. Virtual clusters enable admins to deploy, track and manage containers across various systems to ensure performance, security and. Mark, Thanks for the wonderful article. Nonetheless, considering that the overall overhead is no greater than that of distcc — a solution specifically crafted for distributed compilation — this seems a small price to pay for the benefits of a single system image. What if the application requires a large of CPUs…12, 16 or greater? The optimal configuration for this virtual machine would be 2 Sockets x 5 Cores per Socket, for which vSphere will create 2 vNUMA nodes and distribute 96GB of RAM to each of them. I have always sized my VMs according to the NUMA node size. The Oracle SGA was set to 416 GB and PGA set to 6 GB. Remember, any performance data is a result of the combination of hardware configuration, software configuration, test methodology, test tool, and workload profile used in the testing• It attempts to fit as much vCPUs into the minimum number of virtual NUMA nodes, hence the distribution of 8 vCPU per virtual node. Email: Tell Us About It Our goal is furnish all the information you need to efficiently and effectively use the HECC resources needed for your NASA computational projects. vSphere will now always present the optimal vNUMA topology. 5, how are we best to ensure that high memory but relatively low vCPU workloads are using a vNUMA topology that matches the physical topology? In your situation, it will not trigger the creation of a vNUMA topology as the vCPU count is equal to the core count and thus ESXi will keep all the 16 cores onto a single NUMA node. Anything higher will usually be experiencing some slowness. Assume the DIMMs installed in the server are balanced equally between the NUMA nodes; an equal number of DIMMs per socket and per channel. In this scenario, it is recommended to split up the sockets of the VM so that a vNUMA topology is created for each socket and a configuration of 2 sockets 5 cores will provide a much more optimized VM. Their code pages are easily replicated throughout the cluster and their data pages become locally owned. The challenge is to detect when W rel is to an exclusively-held page, as this cannot be made to trap without making all ordinary writes to the same page fault as well. While traversing the linked list to insert a write, all logically newer writes to the same address are encountered, which are used to constrain the mask of bytes to be written. Conduct Guidelines• Consider an access A that is followed by a write with release semantics W rel. In Windows Server 2012, Hyper-V presents a virtual NUMA topology to virtual machines. Even if a malicious application were to invoke this livelock case, it would not prevent the operating system from taking control and the process could be killed. It is possible that the non-local memory access is involved and application is suffering from performance issues. These PPD allow the VPDs and its vCPUs to map and consume physical 8 cores of the CPU package. NUMA is set to ON at OS and DB level• Example: This table outlines how a virtual machine should be configured on a dual socket 10 core physical host to ensure an optimal vNUMA topology and performance regardless of vSphere version where the assigned memory is greater than that of a pNUMA node. Are there advanced parameters configured to get two 2 vNUMAs created for the VM in the example? No, only virtual machines running NUMA-aware workloads that are large enough to require resources from more than one physical NUMA node, and are not configured to use Dynamic Memory, will benefit from virtual NUMA. Email Address: Follow The Wifi-Cable. I am somewhat confused as I thought 1 core per socket was the recommended configuration. maxPerVirtualNode, and allow the NUMA scheduler to align the NUMA client configuration to the PreferHT setting. For larger VMs — have a host with 2 sockets, 14 cores and 256 GB RAM, 128 GB Memory in one pNUMA. Take a look at the graphic below. This set of observed values is consistent with the Itanium memory consistency model []. Provides the in-guest application the opportunity for optimal self-configuration. This blog contains results that I got in my lab running a load generator SLOB against my workload, which will be way different than any real-world customer workload• Configuring Virtual NUMA Virtual NUMA is configured in the following locations:• If my ESXi hosts are configured with dual socket, 10 core CPUs and 128 GB of memory I know immediately right off the bat the maximum possible size for any large VMs would be 10 vCPU and 64 GB of memory. However, this suggestion has a few shortcomings. So you could continue to leverage hot add for small VM. If a CPU has to access memory owned by another CPU, latency will increase; low performance bandwidth. Migrating VMs configured with Cores per Socket from older ESXi versions to ESXi 6. What would be the optimal CPU configuration for a single VM on this Host? The reason being is that we are running Microsoft Window Server enterprise edition and the limit of max cores is 8. The legend on the upper right provides the ID and command of each user process. These optimizations minimize memory access latencies and reduce memory interconnect traffic. Our algorithm for determining which writes to apply assumes that the network provides causal order delivery, which is a property of typical Ethernet switches c. Write detection at sub-page granularity is a challenge to implement efficiently. The problem with this configuration is that it the virtual NUMA topology does not represent the physical NUMA topology correctly. Lets say I have a Host with 4 Sockets x 8 Cores per Socket and 512 GB RAM slots fully loaded. VMs using many virtual vCPUs are more likely to access more than one NUMA node local memory tied to a on the underlying physical server. These virtual machines will be assigned to cores all within a single NUMA node and will be preferentially allocated memory local to that NUMA node. Oracle ASM was the storage platform with Oracle ASMLIB. When machine is powering up, virtual cores will be distributed to different NUMA nodes and it will improve performance because virtual cores will access to local memory. You will experience the best possible performance for that VM because the memory is always accessed LOCALLY and not remote. Page diffing, as implemented in Munin[] and many later systems, cannot be used by vNUMA, for several reasons. When the application accesses the memory, the OS typically attempts to allocate it on the local or specified NUMA if possible. Physical server is AMD Opteron tm Processor 6378. In this case, remote store atomicity may not hold in vNUMA. Also, it is a good idea to make sure that all VMware Hosts are the same hardware and resource specs as much as possible. A brief description of its usage is provided in the next few sections. The adaptation scheme currently implemented is similar to the read-write-broadcast RWB protocol[] developed for hardware cache coherence. The resulting vNUMA topology will be correct and optimal regardless of the version of vSphere you are using. Now, at first step, I assign 10 sockets to a Linux virtual machine from DL380: When I check NUMA node in the OS, OS says that I have one NUMA node and all cores are scheduled on the node: Now, I assign one socket and 10 cores to the VM, please see the result on VM: We have 1 NUMA node with 10 cores and 1 socket! Using the same example of 16 vCPU, 2 Cores per Socket, on a dual Intel Xeon E5-2630 v4 20 cores in total , the vmdumper one-liner shows the following output in ESXi 6. While discussion of virtualization concepts in general is appropriate, requesting technical help for non-VMware products is off-topic. This behavior can be configured for a specific virtual machine with the numa. So it does make sense to deploy cores per socket and let VMware handle the NUMA presentation to the Guest. Thanks to Frank Denneman for thoroughly documenting them here: Essentially, the vNUMA presentation under vSphere 6. 30197741 218668969 0 0 0xf 2 2 4034560 32768 99 99 vm. Now if your VM is smaller than a pNUMA node, then the benefit may or may not be measurable, since the VM will be scheduled into a 1 pNUMA node. ESXTOP will comma separate each node. So, say, a dual socket, 14 core host. Reliability is not guaranteed, but packet loss is very rare. Specifically, spanning VPDs across PPDs is something that should be avoided at all times. In the scenario of the 16 vCPU VM on the test system, configuring it with 8 Cores per socket, this configuration resembles both the memory and the cache address space of the physical CPU package the most. However, in order to guarantee atomicity of the read and write phases, only one processor at any time can be allowed to perform an atomic operation to a particular location. There are a couple ways to connect the disparate pieces of a multi-cloud architecture. A NUMA architecture divides memory and processors into groups, called NUMA nodes. Use Cases for Oracle NUMA or Non-NUMA The decision to NUMA or not to NUMA for Oracle workloads would depend on several factors including• So, this needs to be accounted for manually. Results presented are a median of the results from at least ten runs of a benchmark. once to False, enable the following advanced host configuration on the ESXi 6. CoreInfo provides the following information: With this new optimization, the virtual NUMA topology corresponds more to the actual physical NUMA topology, allowing the operating system to correctly optimize its processes for correct local and remote memory access. This new decoupling of the corespersocket setting from vNUMA allows vSphere to automatically determine the best vNUMA topology, unless the VMs. There is 512GB of RAM in this host. I have multiple SQL guests that are allocated 8 vCPU and 128GB of RAM. Examples include the efficient emulation of individual instructions, and the use of the performance-monitoring unit PMU to track the execution of specific instructions. We make use of this fact to implement a technique we call incremental deterministic merging. When asking for assistance or advice, please give the community sufficient information to work with. 5, on a dual-socket physical ESXi host with 16 core per socket for a total of 32 physical cores — if you create a four-vSocket virtual machine and set cores per socket to four for a total of 16 vCPUs , vNUMA would have created four vNUMA nodes based on the corespersocket setting. Once in a while, the vnuma command may not produce the display. , Deputy Component Manager NASA High-End Computing Program• Is it just a matter that the CoD feature just increases the available NUMA nodes? The answer is 256 GB of memory. Hi Mark, thanks for the great article. NUMA aware applications like SQL Server database engine will greatly suffer. These virtual machines will be assigned to two or more NUMA nodes and will be preferentially allocated memory local to those NUMA nodes. On this scenario if we want to standardize across the board and knowing that all hosts are 2 Sockets would the SECOND TABLE be the way to go even if some of our VMS have equal or smaller Mem config than the vNUMA node? Windows printing problems are a pain. Oracle ASMFD can also be used instead of Oracle ASMLIB. However, two conditions must be met before vNUMA becomes enabled on a VM:• 00GHz Each Server Memory is Total 191. Inter-node communication vNUMA performance is highly sensitive to communication latency. This is due to a sharp reduction in the number and latency of stalls. The following diagram shows the segregation of cores reserved for Azure Hypervisor and the HB-series VM. The guest OS is presented with 16 CPUs distributed across 8 sockets. Please disregard this statement. In the example screenshot above, 20 vCPUs NumCPUs divided by 10 Cores per Socket NumCoresPerSocket results in 2 Sockets. Thanks again for the write up. maxPerVirtualNode setting in the VM if it is already been powered-on once. Is not meant to be by any way, any final recommendation, whether to enabled NUMA at the database level or not• We use the coalescing feature of Ethernet cards to separate the headers and payload into different buffers to enable zero-copy in the common case in the special case where a local write occurs while a page is being sent, a shadow copy is created. This setting overrides the numa. Next, some of you may be asking what is a NUMA node? In a UMA architecture, access time to a memory location is independent of which processor makes the request or which memory chip contains the transferred data. SEARCH and AGGREGATE barely manage to regain single-node performance on 8 nodes, while SELECT does not scale at all. Now, we have two NUMA nodes and 6 cores are assigned to the first and 4 cores are assigned to the second! note: Just recently AMD released their own flavour of SMT in the Zen architecture. I like to engage people during discussions and I always try to gauge their understanding of the topic first before anything else. For more info about this topic, I suggest reading this article:• 5: As a result of having only two physical NUMA nodes, only two PPDs and VPDs are created. Equal CPU and memory resources results in a balanced host configuration. Restore• 5 vSphere — ESXi will actually ignore it by default. 24x7x365 Help Desk• In other words, a PPD can never span multiple physical CPU packages. See the example for the required script syntax. Again, this is an unbalanced hardware configuration. If lack of progress is detected, then one could fall back to the single-step approach. Related Posts:• The AMD Opteron 6378 is a multi-chip module based on Piledriver architecture. Incoming packets are all received by a single node. Now, what if I assign 20 sockets and 1 core per socket to the machine? AWS re:Invent 2020 launches with a slew of public cloud news announcements, as well as new motions by the company toward hybrid. Or shall I disable it and let the system do its best decision? - Virtual machine performance is consistent between reboots. demonstrating an efficient approach for avoidance of page thrashing. Oracle MySupport Doc ID recommendations about turning NUMA on :• shows an overview of results for each benchmark. As per , A denotes the event of P2 sending a fetch message to P1, B the event of P1 receiving that message and immediately replying to P2, and C the event of P2 receiving the page. Always configure the virtual machine vCPU count to be reflected as Cores per Socket, until you exceed the physical core count of a single physical NUMA node OR until you exceed the total memory available on a single physical NUMA node. Report security issues 24x7x365• Hi, Please correct me in case my understanding is wrong As per my understanding, the numa comes into picture only when we make out of bound VMs i. I guess the big question is — what is the workload and is it NUMA aware? Viewing the results on the Merope front-end node, mfe1, will be supported once the mfe1 operating system is upgraded to SLES 12. The last requirement means that if P1 broadcasts m 1, and P2 broadcasts m 2, then either all other observers observe m 1 before m 2, or all other observers observe m 2 before m 1. Instead, we decided to compromise our goal of full transparency, and require that mf operations are replaced by atomic operations equivalent to a lock-based implementation of mf. If the Remote Physical Pages counter is not zero, comparing it with the total number of memory pages. 5 the size of the VPD is dependent on the number of cores in the CPU package. In , we introduced vNUMA which allows interested guest operating systems to see that they are running on a NUMA Non Uniform Memory Architecture topology. The virtual machine is configured with nine 9 or more vCPUs. As a result, the NUMA spanning setting must be enabled when you have virtual machines that are large enough to be split between two or more physical NUMA nodes. We discuss in detail the enhancements to standard protocols that were required or enabled when implementing DSM inside a hypervisor, and discuss some of the tradeoffs we encountered. The PMU counts mf as a release as well as an acquire , so the above detection mechanism can be used to ensure that writes are ordered correctly across a fence. On some other architectures such as x86, this approach might still result in deadlock, since a single instruction may access several data pages. My physical hosts are 20 core x 2 sockets 40 cores total with 512GB of RAM. 0 and host has 2 sockets and 12 cores each. Is not meant to be by any way, any final recommendation, whether to enable NUMA at the database level or not• Unfortunately, many applications use single threads to create something, but multiple threads distributed across multiple sockets access the data intensively in the future. Here is our scenario: We have two servers, HPE DL580 G8 with 15 cores per socket 120 logical cores and HPE DL380 G8 with 10 cores per socket 40 logical cores.。

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Decoupling of Cores per Socket from Virtual NUMA Topology in vSphere 6.5

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vNUMA: A Virtual Shared

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What is vNUMA (virtual NUMA)?

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To NUMA or not to NUMA

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Understanding vNUMA in vSphere

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