---
title: "Measure the SMT (hyperthreading) gain of the replication-manager host with sysbench"
method: POST
path: "/api/clusters/settings/actions/calibrate-smt-gain"
tags: ["GlobalSetting"]
---

# Measure the SMT (hyperthreading) gain of the replication-manager host with sysbench

`POST /api/clusters/settings/actions/calibrate-smt-gain`

## Request

- The document declares no server URL.
- Auth: none declared. Required headers: `Authorization`

Runs the embedded sysbench (cpu and random memory access, one thread per physical core then every thread, 15 s each) on the host replication-manager runs on, computes the gain and, unless apply=false, writes it to resource-manager-smt-gain. Representative when the infrastructure's nodes share the same hardware. A host without SMT is not an error: the answer says so and nothing is written.

## Query parameters

- `apply` boolean

## Headers

- `Authorization` string, required

## Response `200`

OK

- ServerSMTCalibration
  - `applied` boolean
  - `cores` integer
  - `cpuEventsPerSecCores` number
  - `cpuEventsPerSecThreads` number
  - `cpuGain` number
  - `durationSeconds` integer
  - `gain` number
  - `memGain` number
  - `memMiBPerSecCores` number
  - `memMiBPerSecThreads` number
  - `message` string
  - `threads` integer

## Other responses

- `403`: No valid ACL
- `409`: A calibration is already running
- `500`: Measure failed

## Changes

- **2026-10-12** `d4e4c5013f0c`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/signal18/apis/signal-18-dashboard-api/changes/api/clusters/settings/actions/calibrate-smt-gain/post.md)

---

[API](https://skmtc.dev/signal18/apis/signal-18-dashboard-api.md) - [All operations](https://skmtc.dev/signal18/apis/signal-18-dashboard-api/llms.txt) - [OpenAPI document](https://skmtc.dev/signal18/apis/signal-18-dashboard-api/revisions/8ee8a1e31294?raw)