VkPerfHintInfoQCOM

The VkPerfHintInfoQCOM structure is defined as:

typedef struct VkPerfHintInfoQCOM {
    VkStructureType sType;
    void* pNext;
    VkPerfHintTypeQCOM type;
    uint32_t scale;
} VkPerfHintInfoQCOM;

pub struct PerfHintInfoQCOM {
    s_type: vk::StructureType,
    p_next: *mut c_void, // Pointer to next structure
    type: vk::PerfHintTypeQCOM,
    scale: u32,
}

• sType is a VkStructureType value identifying this structure.
• pNext is NULL or a pointer to a structure extending this structure.
• type is a VkPerfHintTypeQCOM value indicating the type of performance hint to apply.
• scale is a normalized fixed-point scale factor.

The device has two global frequency constraints, f_min and f_max, that can be influenced by the VK_PERF_HINT_TYPE_FREQUENCY_MIN_QCOM, VK_PERF_HINT_TYPE_FREQUENCY_MAX_QCOM, and VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM performance hints. These constraints determine the range of clock frequencies that the platform performance algorithms may select from. If no constraints are set, f_min and f_max are set to the minimum and maximum frequencies the device can support, F_min and F_max respectively.

The f_min constraint applied by VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM is calculated with the following:

• $f\_{min} = \lfloor\frac{scale}{100} \times F\_{max}\rfloor$

The implementation rounds f_min down to the next available lower frequency the device supports, clamped to F_min.

The global frequency constraints are determined by combining the performance hints from all of the device’s active queues of all processes on the host. Performance hints that influence device frequency are ranked, where a higher ranked hint supersedes all lower ranked hints. These are listed in order of highest rank to lowest:

• VK_PERF_HINT_TYPE_FREQUENCY_MAX_QCOM
• VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM and scale equal to 100
• VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM and scale equal to 99
• VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM and scale equal to 98
• …​
• VK_PERF_HINT_TYPE_FREQUENCY_SCALED_QCOM and scale equal to 0
• VK_PERF_HINT_TYPE_DEFAULT_QCOM
• VK_PERF_HINT_TYPE_FREQUENCY_MIN_QCOM