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[Refactor] (MG_State, MG_Backend): PipeResource storage layer + zero-copy coherent persistent maps

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Introduce a Mesa pipe_resource-style PipeResource that owns a GL buffer's bytes
and its backend GPU resource, abstracting WHERE the authoritative bytes live:
 - Shadow mode (non-persistent buffers): a CPU Vector; the backend keeps its own
   GPU copy in sync via BufferBackendOps, exactly as before.
 - Persistent mode (coherent GL_MAP_PERSISTENT maps): the backend's host-visible,
   COHERENT, persistently-mapped GPU memory is the single source of truth. The app
   writes into it directly, every reader resolves against it, and NO per-write
   backend transfer happens. The CPU shadow is released.

BufferObject no longer owns a raw shadow Vector; it holds a PipeResource and
exposes one accessor, MappedData(), that all readers go through. Every buffer-data
consumer (UBO payload, PBO texture upload, indirect draws, resident/streamed
uploads, both backends) was migrated from GetDataReadOnly()->data() to
MappedData(), so a persistent buffer's readers see GPU memory - not a stale
shadow. That stale-shadow inconsistency is what corrupted rendering (wrong UBOs ->
misplaced/"lost" vertices) in the first zero-copy attempt (625c8a6, reverted in
896cafc); routing every consumer through one accessor makes it structurally
impossible.

Backends provide the map via BufferBackendOps::AcquirePersistentMap:
 - DirectVulkan: a HOST_VISIBLE|HOST_COHERENT (required, not just requested),
   persistently mapped resident VkBuffer carrying every usage, seeded from the
   shadow, never recreated; AcquireResidentSlice binds it directly.
 - DirectGLES: EXT_buffer_storage immutable persistent+coherent glMapBufferRange,
   falling back to the shadow when the extension is absent.

Fixes the ~7GB GpuMemory OOM + 100%-CPU/ANR running modern Blaze3D Minecraft on
both Magma and Espryt (per-draw whole-buffer re-upload of the coherent persistent
ring buffer), without the coherency/stale-read hazards of the reverted attempt.

BufferTest: zero-copy stress guard (15,360 draws -> 0 per-draw transfers, and every
reader resolves to GPU memory) + a shadow-fallback test. Host suite: 203/203 pass.
Device verification pending.
This commit is contained in:
swung0x48
2026-07-11 20:18:38 -04:00
parent 0f99d93300
commit c1743aa42d
15 changed files with 577 additions and 101 deletions
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MobileGL/MG_Backend/DirectGLES/Managers.cpp
+86 -3
View File
@@ -293,7 +293,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
const GLenum usage = MG_Util::ConvertBufferUsageToGLEnum(bufferObject.GetUsage());
BindBufferId(TempBufferTarget, resource.id);
g_GLESFuncs.glBufferData(TempBufferTarget, (GLsizeiptr)size,
size > 0 ? bufferObject.GetDataReadOnly()->data() : nullptr, usage);
size > 0 ? bufferObject.MappedData() : nullptr, usage);
resource.storageSize = size;
resource.storageInitialized = true;
resource.pendingRespecify = false;
@@ -315,12 +315,83 @@ namespace MobileGL::MG_Backend::DirectGLES {
if (start >= end) return;
BindBufferId(TempBufferTarget, resource.id);
g_GLESFuncs.glBufferSubData(TempBufferTarget, (GLintptr)start, (GLsizeiptr)(end - start),
bufferObject.GetDataReadOnly()->data() + start);
bufferObject.MappedData() + start);
}
// EXT_buffer_storage bit values (same numeric values as the desktop ARB
// tokens); defined locally so this compiles regardless of which GLES headers
// expose the EXT tokens.
constexpr GLbitfield kMapPersistentBit = 0x0040;
constexpr GLbitfield kMapCoherentBit = 0x0080;
constexpr GLbitfield kDynamicStorageBit = 0x0100;
// Zero-copy persistent map: back the buffer with real immutable,
// persistently+coherently mapped GL storage (EXT_buffer_storage) and hand the
// app that mapped pointer (adopted by the frontend PipeResource). Returns
// nullptr when the extension is unavailable or the context is not current, in
// which case the frontend keeps its CPU-shadow model. Idempotent.
void* Ops_AcquirePersistentMap(BufferObject& bufferObject) {
if (!CanTouchGLNow() || !g_GLESFuncs.glBufferStorageEXT || !g_GLESFuncs.glMapBufferRange ||
!g_GLESFuncs.glGenBuffers) {
return nullptr;
}
const SizeT size = bufferObject.GetSize();
if (size == 0) return nullptr;
auto* resource = static_cast<GLESBufferResource*>(bufferObject.GetBackendResource().get());
if (!resource) {
auto created = MakeShared<GLESBufferResource>();
resource = created.get();
bufferObject.SetBackendResource(std::move(created));
}
resource->contextGeneration = g_bufferContextGeneration;
if (resource->persistentMapped && resource->persistentPtr && resource->storageSize == size) {
return resource->persistentPtr; // idempotent
}
// Need a fresh id: glBufferStorage fails on a buffer that already has
// immutable storage, and any prior mutable store is replaced anyway.
if (resource->id != 0) {
g_GLESFuncs.glDeleteBuffers(1, &resource->id);
resource->id = 0;
}
g_GLESFuncs.glGenBuffers(1, &resource->id);
if (resource->id == 0) return nullptr;
// Seed from the shadow (MappedData() is still the shadow: the frontend
// adopts and drops it only after this returns).
BindBufferId(TempBufferTarget, resource->id);
const void* initial = bufferObject.MappedData();
g_GLESFuncs.glBufferStorageEXT(TempBufferTarget, static_cast<GLsizeiptr>(size), initial,
GL_MAP_WRITE_BIT | kMapPersistentBit | kMapCoherentBit |
kDynamicStorageBit);
void* ptr = g_GLESFuncs.glMapBufferRange(TempBufferTarget, 0, static_cast<GLsizeiptr>(size),
GL_MAP_WRITE_BIT | kMapPersistentBit | kMapCoherentBit);
if (!ptr) {
MGLOG_E("Ops_AcquirePersistentMap: glMapBufferRange(persistent) failed for buffer %u",
resource->id);
resource->persistentMapped = false;
resource->persistentPtr = nullptr;
return nullptr;
}
resource->persistentPtr = ptr;
resource->persistentMapped = true;
resource->storageSize = size;
resource->storageInitialized = true;
resource->pendingRespecify = false;
{
const std::lock_guard<std::mutex> lock(resource->pendingMutex);
resource->pendingRanges.clear();
}
resource->syncedChangeSerial = bufferObject.GetChangeSerial();
return ptr;
}
void Ops_Respecify(BufferObject& bufferObject) {
auto* resource = ResourceOf(bufferObject);
if (!resource) return; // lazy: EnsureBufferResource full-uploads on creation
if (resource->persistentMapped) return; // immutable persistent storage is never respecified
if (!CanTouchGLNow() || resource->id == 0 ||
resource->contextGeneration != g_bufferContextGeneration) {
resource->pendingRespecify = true;
@@ -380,7 +451,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
GL_MAP_WRITE_BIT | (invalidate ? GL_MAP_INVALIDATE_RANGE_BIT : 0) |
(unsynchronized ? GL_MAP_UNSYNCHRONIZED_BIT : 0));
if (mappedData) {
Memcpy(mappedData, bufferObject.GetDataReadOnly()->data() + range.start,
Memcpy(mappedData, bufferObject.MappedData() + range.start,
range.end - range.start);
g_GLESFuncs.glUnmapBuffer(TempBufferTarget);
resource->syncedChangeSerial = bufferObject.GetChangeSerial();
@@ -419,6 +490,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
.SubData = Ops_SubData,
.FlushMappedRange = Ops_FlushMappedRange,
.OnDestroy = Ops_OnDestroy,
.AcquirePersistentMap = Ops_AcquirePersistentMap,
};
} // namespace
@@ -491,6 +563,17 @@ namespace MobileGL::MG_Backend::DirectGLES {
resource->pendingRespecify = true;
resource->pendingRanges.clear();
resource->contextGeneration = g_bufferContextGeneration;
// The persistent map (and its pointer) died with the old context; the
// frontend re-acquires a fresh one on its next map.
resource->persistentMapped = false;
resource->persistentPtr = nullptr;
}
// Zero-copy coherent persistent buffer: the app writes straight into the
// persistently mapped immutable store, so there is nothing to (re)upload at
// draw time. This is where the per-draw whole-buffer glBufferSubData used to run.
if (resource->persistentMapped && resource->persistentPtr && resource->id != 0) {
return resource;
}
if (resource->id == 0) {