Cloud servers with dedicated cores
A cloud server with dedicated cores is a cloud server with vCPUs that are tied to the threads of specific physical processor cores rather than switching between threads of different cores.
Dedicated cores guarantee that the cloud server uses processor resources without competing for computing power with other cloud servers. Such isolation:
- provides the cloud server with stable performance;
- protects the cloud server from hardware vulnerabilities (such as Spectre, Meltdown, and others) caused by other cloud servers on the same physical node.
Configuring dedicated cores is available when creating a cloud server or changing a cloud server configuration.
For a cloud server with dedicated cores, the Hyper-Threading (SMT) option is enabled by default. You can also configure mandatory resource placement on a single NUMA node.
Use cases
Suitable for high-load and performance-critical systems that require predictable and stable vCPU performance without the influence of other cloud servers:
- for running resource-intensive databases;
- for processing analytical tasks and tasks with high computational complexity;
- for running CI/CD servers;
- for hosting game servers and real-time applications requiring low latency;
- for deploying microservices and high-request-rate APIs;
- for ensuring stable monitoring and logging performance during high event rates.
Hyper-Threading
Hyper-Threading (SMT or Hyper-Threading) is a technology that allows a single physical processor core to process two threads simultaneously. In this case, each pair of vCPU of the cloud server corresponds to two threads of one physical processor core.
This technology improves performance in multithreaded tasks, for example, when running web servers and enterprise applications or during video rendering and processing. Learn more about the technology and how it works in the Selectel blog post What is Hyper-Threading.
On cloud servers with dedicated cores, Hyper-Threading (SMT) is enabled by default. It is not possible to enable Hyper-Threading (SMT) for cloud servers without dedicated cores.
For databases, high-performance computing (HPC) tasks, or software licensed by physical cores, we recommend testing system performance with the Hyper-Threading (SMT) option both enabled and disabled. If necessary, you can disable the option:
- for stable performance in single-threaded scenarios;
- for task isolation at the physical core level;
- for license compliance.
When you disable the Hyper-Threading (SMT) option, threads are disabled — each vCPU of the cloud server corresponds to a whole physical processor core. The number of vCPUs on the cloud server is halved.
For example, you create a cloud server with the Hyper-Threading (SMT) option enabled and 8 vCPUs. The cloud server will use 4 physical cores, each operating in Hyper-Threading (SMT) mode, which means it processes 2 threads. Thus, the cloud server has 8 vCPUs.
If you disable the Hyper-Threading (SMT) option, the number of vCPUs on the cloud server will be reduced to 4, which will correspond to the number of physical cores rather than the number of threads. The number of occupied physical cores will remain the same, so the cloud server cost will not change.
If, when changing the configuration of a cloud server, you only enable or disable the Hyper-Threading (SMT) setting, perform a hard reboot.
Before disabling Hyper-Threading (SMT), make sure to test application performance under load — some applications may run slower without Hyper-Threading (SMT).
Mandatory resource placement on a single NUMA node
NUMA (Non-Uniform Memory Access) is an architecture for multiprocessor systems. NUMA nodes are architectural blocks in multiprocessor systems where a node includes a single processor and local RAM, to which the processor inside the node has fast access with low latency.
When resources are placed on a single NUMA node, the cloud server operates only within the node — using CPU cores and local memory attached to the node. This contributes to minimal latency when working with memory.
You can enable mandatory resource placement for a cloud server on a single NUMA node when creating a cloud server or changing a cloud server configuration only with dedicated cores and starting from 4 vCPUs. Enabling mandatory resource placement on a single NUMA node is not available for cloud servers without dedicated cores.
If the cloud server resources cannot be placed on a single NUMA node, the server will not be created.
Limitations
Cloud servers with dedicated cores are available only in the pool segments ru-3b, ru-7a, ru-7b, and all segments of the multi-AZ pool ru-6.
Configuring dedicated cores is available only in the Standard and HighFreq lines. You can see the list of fixed configuration flavors for lines that support dedicated cores in the List of fixed configuration flavors in all pools table.
Cost
You can view the cost of a cloud server with dedicated cores, the Hyper-Threading (SMT) option, and the option for mandatory placement on a single NUMA node on selectel.ru.
The cost of a cloud server with dedicated cores does not change:
-
when the Hyper-Threading (SMT) option is enabled or disabled;
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when the mandatory placement on a single NUMA node option is enabled or disabled.