AMD Linux Driver Readying Peak Tops Limiter "PTL" Support
The AMDGPU and AMDKFD Linux kernel graphics driver code has been readying support for the Peak Tops Limiter (PTL) as a new feature to the latest Instinct accelerators.
AMD's Peak Tops Limiter is supported by the latest AMD GFX 9.4.4 IP for Instinct. The hardware-based feature allows limiting the peak computational throughput for staying within desired power and thermal budgets.
The Peak Tops Limiter can be controlled on a per-GPU/accelerator basis with the user controls living under the /sys/class/drm/cardX/device/ptl/ sysfs interface. There is support with ptl_enable for toggling whether the feature is enabled, ptl_supported_formats as the supported data type formats that can be limited, and then ptl_format for the user being able to specify two preferred formats for this PTL feature. Besides these direct sysfs interfaces that require root access, AMD has also been preparing Peak Tops Limiter APIs for their AMD SMI library and ROCm for developers to provide this opt-in support for limiting computational throughput for achieving power/thermal objectives.
There is also a new IOCTL option for user-space explicit control over the PTL state for profiling. The patches also add a amdgpu.ptl= kernel module option to allow enabling/disabling or permanently disabling the AMD PTL feature at boot time.
When enabled and set, the AMD Peak Tops Limiter will dynamically adjust the engine frequency for ensuring the delivered TOPS never exceeds the defined TOPS limit.
This Peak Tops Limiter support for the AMDGPU/AMDKFD kernel driver code is currently under review and given the timing it will not be found in the current v7.0 cycle. More details on this Peak Tops Limiter feature for Instinct hardware can be found via this patch series.
AMD's Peak Tops Limiter is supported by the latest AMD GFX 9.4.4 IP for Instinct. The hardware-based feature allows limiting the peak computational throughput for staying within desired power and thermal budgets.
The Peak Tops Limiter can be controlled on a per-GPU/accelerator basis with the user controls living under the /sys/class/drm/cardX/device/ptl/ sysfs interface. There is support with ptl_enable for toggling whether the feature is enabled, ptl_supported_formats as the supported data type formats that can be limited, and then ptl_format for the user being able to specify two preferred formats for this PTL feature. Besides these direct sysfs interfaces that require root access, AMD has also been preparing Peak Tops Limiter APIs for their AMD SMI library and ROCm for developers to provide this opt-in support for limiting computational throughput for achieving power/thermal objectives.
There is also a new IOCTL option for user-space explicit control over the PTL state for profiling. The patches also add a amdgpu.ptl= kernel module option to allow enabling/disabling or permanently disabling the AMD PTL feature at boot time.
When enabled and set, the AMD Peak Tops Limiter will dynamically adjust the engine frequency for ensuring the delivered TOPS never exceeds the defined TOPS limit.
This Peak Tops Limiter support for the AMDGPU/AMDKFD kernel driver code is currently under review and given the timing it will not be found in the current v7.0 cycle. More details on this Peak Tops Limiter feature for Instinct hardware can be found via this patch series.