CONFIG_SWIOTLB_DEFAULT_SIZE_MB: Default SWIOTLB bounce buffer size in MB

General informations

The Linux kernel configuration item CONFIG_SWIOTLB_DEFAULT_SIZE_MB:

• prompt: Default SWIOTLB bounce buffer size in MB
• type: int
• depends on: CONFIG_SWIOTLB
• defined in kernel/dma/Kconfig
• found in Linux kernels: 7.3-rc+HEAD

Help text

Sets the default size of the software IO TLB (SWIOTLB) bounce buffer pool allocated at boot time. The default is 64 MB.

On memory-constrained embedded or mobile platforms (e.g., those with a hardware IOMMU such as ARM SMMU covering most DMA-capable devices), a smaller value such as 4 or 8 MB may be sufficient. The SWIOTLB is then only needed for devices that bypass the IOMMU or have restricted DMA address ranges.

The minimum allowed value is 1 MB. This compile-time default can be overridden at runtime using the "swiotlb=<nslabs>" kernel command line parameter. Refer to Documentation/admin-guide/kernel-parameters.txt for details.

If unsure, leave at the default value of 64.

Hardware

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The data is retrived from:

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