Tuning BIOS

Method

The system memory management unit (SMMU) is an address translation bridge between an I/O device and a bus bridge. It translates a virtual address to a physical address and performs permission control and cache management on memory access, ensuring secure and efficient use of the system memory. The database consumes a large amount of memory and I/O resources while the SMMU increases extra overhead and latency, which deteriorates the system performance. Therefore, enabling the SMMU cannot achieve better performance in database scenarios and disabling the SMMU can help reduce the system complexity and maintenance cost. Therefore, it is advised to disable the SMMU in the BIOS for Kunpeng platforms.

By tracing changes of instructions and data addresses, hardware prefetching reads the instructions and addresses to the cache in advance. Hardware prefetching affects the database performance. Therefore, it is advised to disable it in the BIOS.

By tracing changes of instructions and data addresses, hardware prefetching reads the instructions and addresses to the cache in advance. Hardware prefetching affects the database performance. In online transaction processing (OLTP) scenarios, you are advised to disable the prefetching function for servers that use new Kunpeng 920 processor models. In online analytical processing (OLAP) scenarios where prefetching function is optimized, you are advised to enable it for servers that use new Kunpeng 920 processor models.

In the BIOS settings, the memory refresh rate can be set to the Auto option, which automatically adjusts the memory refresh rate based on the operating temperature. Compared with the default 32 ms option, the automatic refresh can improve memory performance. In addition, this option ensures that memory data is reliable when the operating temperature ranges from 85°C to 95°C.

In high-performance scenarios, you are advised to set the Power Policy to Performance Mode to ensure that the CPU always runs at the highest frequency.

• Disable the SMMU.
  

  Disable the SMMU feature only in non-virtualization scenarios. In virtualization scenarios, enable it.

  1. Restart the server and enter the BIOS.

     For details, see "Accessing the BIOS" in TaiShan Server BIOS Parameter Reference (Kunpeng 920 Processor).

  2. Choose Advanced > MISC Config and press Enter.
  3. Set Support Smmu to Disabled.
• (In OLTP scenarios) Disable hardware prefetching.
  1. In the BIOS, choose Advanced > MISC Config and press Enter.
  2. Set CPU Prefetching Configuration to Disabled, and press F10 to save the settings and exit.
• (In OLAP scenarios) Enable hardware prefetching.
  1. In the BIOS, choose Advanced > MISC Config and press Enter.
  2. Set CPU Prefetching Configuration to Enabled, and press F10 to save the settings and exit.
• Set the memory refresh rate to Auto.
  1. Restart the server and enter the BIOS.

     For details, see "Accessing the BIOS" in TaiShan Server BIOS Parameter Reference (Kunpeng 920 Processor).

  2. Choose Advanced > Memory Config > Custom Refresh Rate and press Enter.
  3. Set Custom Refresh Rate to Auto and press F10 to save the settings and exit.
• Set Power Policy to Performance Mode.
  1. Restart the server and enter the BIOS.

     For details, see "Accessing the BIOS" in TaiShan Server BIOS Parameter Reference (Kunpeng 920 Processor).

  2. Choose BIOS > Advanced > Performance Config > Power Policy and press Enter.
  3. Set Power Policy to Performance and press F10 to save the settings and exit.