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Vulkan: Add a DriverDetails bug for "slow cached readback memory"

Using the cached memory type appears to be slower on Mali drivers, with
~10-15% CPU spent in the __pi___inval_cache_range kernel function.
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stenzek committed Oct 2, 2019
1 parent c557aa4 commit 328d89db708ec9c1d3e31a760f530b64c4767b2b
@@ -775,6 +775,16 @@ u32 VulkanContext::GetReadbackMemoryType(u32 bits, bool* is_coherent)
{
std::optional<u32> type_index;

// Mali driver appears to be significantly slower for readbacks when using cached memory.
if (DriverDetails::HasBug(DriverDetails::BUG_SLOW_CACHED_READBACK_MEMORY))
{
type_index = GetMemoryType(
bits, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT, true,
is_coherent);
if (type_index)
return type_index.value();
}

// Optimal config uses cached+coherent.
type_index =
GetMemoryType(bits,
@@ -113,7 +113,11 @@ constexpr BugInfo m_known_bugs[] = {
{API_VULKAN, OS_ALL, VENDOR_QUALCOMM, DRIVER_QUALCOMM, Family::UNKNOWN,
BUG_BROKEN_REVERSED_DEPTH_RANGE, -1.0, -1.0, true},
{API_VULKAN, OS_OSX, VENDOR_ALL, DRIVER_PORTABILITY, Family::UNKNOWN,
BUG_BROKEN_REVERSED_DEPTH_RANGE, -1.0, -1.0, true}};
BUG_BROKEN_REVERSED_DEPTH_RANGE, -1.0, -1.0, true},
{API_VULKAN, OS_ALL, VENDOR_ARM, DRIVER_ARM, Family::UNKNOWN, BUG_SLOW_CACHED_READBACK_MEMORY,
-1.0, -1.0, true},
{API_VULKAN, OS_ALL, VENDOR_QUALCOMM, DRIVER_QUALCOMM, Family::UNKNOWN,
BUG_SLOW_CACHED_READBACK_MEMORY, -1.0, -1.0, true}};

static std::map<Bug, BugInfo> m_bugs;

@@ -281,6 +281,11 @@ enum Bug
// The Vulkan spec allows the minDepth/maxDepth fields in the viewport to be reversed,
// however the implementation is broken on some drivers.
BUG_BROKEN_REVERSED_DEPTH_RANGE,

// BUG: Cached memory is significantly slower for readbacks than coherent memory in the
// Mali Vulkan driver, causing high CPU usage in the __pi___inval_cache_range kernel
// function. This flag causes readback buffers to select the coherent type.
BUG_SLOW_CACHED_READBACK_MEMORY,
};

// Initializes our internal vendor, device family, and driver version

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