Tuning BIOS

Purpose

Configure advanced BIOS settings to improve server performance.

Procedure

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 number of memory and I/O resources while the SMMU increases extra overhead and latency, which deteriorates the system performance. Therefore, enabling the SMMU does not bring higher performance in database scenarios but can help reduce the system complexity and maintenance cost. Therefore, it is recommended that the SMMU be disabled in the BIOS on the Kunpeng platform.

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

1. Disable the System Memory Management Unit (SMMU).
   

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

   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 Disable.
2. Disable prefetch.
   1. In the BIOS, choose Advanced > MISC Config and press Enter.
   2. Set CPU Prefetching Configuration to Disabled, and press F10.