rhi: Manage buffer data without QBA

Use a simple and straightforward container that only does what
we need here.

Change-Id: I1a81b53a58bc91d533e3d7df5471a1362046825d
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

9 files changed, 119 insertions, 63 deletions

diff --git a/src/gui/rhi/qrhi_p_p.h b/src/gui/rhi/qrhi_p_p.h
index 3b68b5d078..1316321694 100644
--- a/src/gui/rhi/qrhi_p_p.h
+++ b/src/gui/rhi/qrhi_p_p.h
@@ -277,6 +277,80 @@ bool qrhi_toTopLeftRenderTargetRect(const QSize &outputSize, const std::array<T,
     return true;
 }
 
+struct QRhiBufferDataPrivate
+{
+    Q_DISABLE_COPY_MOVE(QRhiBufferDataPrivate)
+    QRhiBufferDataPrivate() { }
+    ~QRhiBufferDataPrivate() { delete[] largeData; }
+    int ref = 1;
+    int size = 0;
+    int largeAlloc = 0;
+    char *largeData = nullptr;
+    static constexpr int SMALL_DATA_SIZE = 1024;
+    char data[SMALL_DATA_SIZE];
+};
+
+// no detach-with-contents, no atomic refcount, no shrink
+class QRhiBufferData
+{
+public:
+    QRhiBufferData() = default;
+    ~QRhiBufferData()
+    {
+        if (d && !--d->ref)
+            delete d;
+    }
+    QRhiBufferData(const QRhiBufferData &other)
+        : d(other.d)
+    {
+        if (d)
+            d->ref += 1;
+    }
+    QRhiBufferData &operator=(const QRhiBufferData &other)
+    {
+        if (d == other.d)
+            return *this;
+        if (other.d)
+            other.d->ref += 1;
+        if (d && !--d->ref)
+            delete d;
+        d = other.d;
+        return *this;
+    }
+    const char *constData() const
+    {
+        return d->size <= QRhiBufferDataPrivate::SMALL_DATA_SIZE ? d->data : d->largeData;
+    }
+    int size() const
+    {
+        return d->size;
+    }
+    void assign(const char *s, int size)
+    {
+        if (!d) {
+            d = new QRhiBufferDataPrivate;
+        } else if (d->ref != 1) {
+            d->ref -= 1;
+            d = new QRhiBufferDataPrivate;
+        }
+        d->size = size;
+        if (size <= QRhiBufferDataPrivate::SMALL_DATA_SIZE) {
+            memcpy(d->data, s, size);
+        } else {
+            if (d->largeAlloc < size) {
+                delete[] d->largeData;
+                d->largeAlloc = size;
+                d->largeData = new char[size];
+            }
+            memcpy(d->largeData, s, size);
+        }
+    }
+private:
+    QRhiBufferDataPrivate *d = nullptr;
+};
+
+Q_DECLARE_TYPEINFO(QRhiBufferData, Q_MOVABLE_TYPE);
+
 class QRhiResourceUpdateBatchPrivate
 {
 public:
@@ -289,8 +363,7 @@ public:
         Type type;
         QRhiBuffer *buf;
         int offset;
-        QByteArray data;
-        int dataSize; // the real number of currently used bytes in data, not the same as data.size()
+        QRhiBufferData data;
         int readSize;
         QRhiBufferReadbackResult *result;
 
@@ -301,8 +374,7 @@ public:
             op.buf = buf;
             op.offset = offset;
             const int effectiveSize = size ? size : buf->size();
-            op.data = QByteArray(reinterpret_cast<const char *>(data), effectiveSize);
-            op.dataSize = effectiveSize;
+            op.data.assign(reinterpret_cast<const char *>(data), effectiveSize);
             return op;
         }
 
@@ -312,28 +384,7 @@ public:
             op->buf = buf;
             op->offset = offset;
             const int effectiveSize = size ? size : buf->size();
-
-            // Why the isDetached check? Simply because the cost of detaching
-            // with a larger allocation may be a lot higher than creating a new
-            // deep copy bytearray with our (potentially lot smaller) data.
-            // This reduces the benefits with certain backends (e.g. Vulkan)
-            // that hold on to the data (implicit sharing!) of host visible
-            // buffers for the current and next frame (assuming 2 frames in
-            // flight), but it is still an improvement (enabled by
-            // nextResourceUpdateBatch's shuffling when choosing a free batch
-            // from the pool). For other backends (e.g. D3D11) this can reduce
-            // mallocs (caused by creating new deep copy bytearrays) almost
-            // completely after a few frames (assuming of course that no
-            // dynamic elements with larger buffer data appear).
-
-            if (op->data.isDetached()) {
-                if (op->data.size() < effectiveSize)
-                    op->data.resize(effectiveSize);
-                memcpy(op->data.data(), data, effectiveSize);
-            } else {
-                op->data = QByteArray(reinterpret_cast<const char *>(data), effectiveSize);
-            }
-            op->dataSize = effectiveSize;
+            op->data.assign(reinterpret_cast<const char *>(data), effectiveSize);
         }
 
         static BufferOp staticUpload(QRhiBuffer *buf, int offset, int size, const void *data)
@@ -343,8 +394,7 @@ public:
             op.buf = buf;
             op.offset = offset;
             const int effectiveSize = size ? size : buf->size();
-            op.data = QByteArray(reinterpret_cast<const char *>(data), effectiveSize);
-            op.dataSize = effectiveSize;
+            op.data.assign(reinterpret_cast<const char *>(data), effectiveSize);
             return op;
         }
 
@@ -354,14 +404,7 @@ public:
             op->buf = buf;
             op->offset = offset;
             const int effectiveSize = size ? size : buf->size();
-            if (op->data.isDetached()) {
-                if (op->data.size() < effectiveSize)
-                    op->data.resize(effectiveSize);
-                memcpy(op->data.data(), data, effectiveSize);
-            } else {
-                op->data = QByteArray(reinterpret_cast<const char *>(data), effectiveSize);
-            }
-            op->dataSize = effectiveSize;
+            op->data.assign(reinterpret_cast<const char *>(data), effectiveSize);
         }
 
         static BufferOp read(QRhiBuffer *buf, int offset, int size, QRhiBufferReadbackResult *result)
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index 1c7f3cd17a..2fe138dd55 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -1418,17 +1418,17 @@ void QRhiD3D11::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
         if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::DynamicUpdate) {
             QD3D11Buffer *bufD = QRHI_RES(QD3D11Buffer, u.buf);
             Q_ASSERT(bufD->m_type == QRhiBuffer::Dynamic);
-            memcpy(bufD->dynBuf + u.offset, u.data.constData(), size_t(u.dataSize));
+            memcpy(bufD->dynBuf + u.offset, u.data.constData(), size_t(u.data.size()));
             bufD->hasPendingDynamicUpdates = true;
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::StaticUpload) {
             QD3D11Buffer *bufD = QRHI_RES(QD3D11Buffer, u.buf);
             Q_ASSERT(bufD->m_type != QRhiBuffer::Dynamic);
-            Q_ASSERT(u.offset + u.dataSize <= bufD->m_size);
+            Q_ASSERT(u.offset + u.data.size() <= bufD->m_size);
             QD3D11CommandBuffer::Command cmd;
             cmd.cmd = QD3D11CommandBuffer::Command::UpdateSubRes;
             cmd.args.updateSubRes.dst = bufD->buffer;
             cmd.args.updateSubRes.dstSubRes = 0;
-            cmd.args.updateSubRes.src = cbD->retainData(u.data);
+            cmd.args.updateSubRes.src = cbD->retainBufferData(u.data);
             cmd.args.updateSubRes.srcRowPitch = 0;
             // Specify the region (even when offset is 0 and all data is provided)
             // since the ID3D11Buffer's size is rounded up to be a multiple of 256
@@ -1437,7 +1437,7 @@ void QRhiD3D11::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
             box.left = UINT(u.offset);
             box.top = box.front = 0;
             box.back = box.bottom = 1;
-            box.right = UINT(u.offset + u.dataSize); // no -1: right, bottom, back are exclusive, see D3D11_BOX doc
+            box.right = UINT(u.offset + u.data.size()); // no -1: right, bottom, back are exclusive, see D3D11_BOX doc
             cmd.args.updateSubRes.hasDstBox = true;
             cmd.args.updateSubRes.dstBox = box;
             cbD->commands.append(cmd);
diff --git a/src/gui/rhi/qrhid3d11_p_p.h b/src/gui/rhi/qrhid3d11_p_p.h
index 7c13544276..b89b6f5124 100644
--- a/src/gui/rhi/qrhid3d11_p_p.h
+++ b/src/gui/rhi/qrhid3d11_p_p.h
@@ -473,6 +473,7 @@ struct QD3D11CommandBuffer : public QRhiCommandBuffer
     quint32 currentVertexOffsets[D3D11_IA_VERTEX_INPUT_RESOURCE_SLOT_COUNT];
 
     QVarLengthArray<QByteArray, 4> dataRetainPool;
+    QVarLengthArray<QRhiBufferData, 4> bufferDataRetainPool;
     QVarLengthArray<QImage, 4> imageRetainPool;
 
     // relies heavily on implicit sharing (no copies of the actual data will be made)
@@ -480,6 +481,10 @@ struct QD3D11CommandBuffer : public QRhiCommandBuffer
         dataRetainPool.append(data);
         return reinterpret_cast<const uchar *>(dataRetainPool.last().constData());
     }
+    const uchar *retainBufferData(const QRhiBufferData &data) {
+        bufferDataRetainPool.append(data);
+        return reinterpret_cast<const uchar *>(bufferDataRetainPool.last().constData());
+    }
     const uchar *retainImage(const QImage &image) {
         imageRetainPool.append(image);
         return imageRetainPool.last().constBits();
@@ -487,6 +492,7 @@ struct QD3D11CommandBuffer : public QRhiCommandBuffer
     void resetCommands() {
         commands.clear();
         dataRetainPool.clear();
+        bufferDataRetainPool.clear();
         imageRetainPool.clear();
     }
     void resetState() {
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 372bf39c3e..c1ea444c50 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -1697,7 +1697,7 @@ void QRhiGles2::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
             QGles2Buffer *bufD = QRHI_RES(QGles2Buffer, u.buf);
             Q_ASSERT(bufD->m_type == QRhiBuffer::Dynamic);
             if (bufD->m_usage.testFlag(QRhiBuffer::UniformBuffer)) {
-                memcpy(bufD->ubuf + u.offset, u.data.constData(), size_t(u.dataSize));
+                memcpy(bufD->ubuf + u.offset, u.data.constData(), size_t(u.data.size()));
             } else {
                 trackedBufferBarrier(cbD, bufD, QGles2Buffer::AccessUpdate);
                 QGles2CommandBuffer::Command cmd;
@@ -1705,16 +1705,16 @@ void QRhiGles2::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
                 cmd.args.bufferSubData.target = bufD->targetForDataOps;
                 cmd.args.bufferSubData.buffer = bufD->buffer;
                 cmd.args.bufferSubData.offset = u.offset;
-                cmd.args.bufferSubData.size = u.dataSize;
-                cmd.args.bufferSubData.data = cbD->retainData(u.data);
+                cmd.args.bufferSubData.size = u.data.size();
+                cmd.args.bufferSubData.data = cbD->retainBufferData(u.data);
                 cbD->commands.append(cmd);
             }
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::StaticUpload) {
             QGles2Buffer *bufD = QRHI_RES(QGles2Buffer, u.buf);
             Q_ASSERT(bufD->m_type != QRhiBuffer::Dynamic);
-            Q_ASSERT(u.offset + u.dataSize <= bufD->m_size);
+            Q_ASSERT(u.offset + u.data.size() <= bufD->m_size);
             if (bufD->m_usage.testFlag(QRhiBuffer::UniformBuffer)) {
-                memcpy(bufD->ubuf + u.offset, u.data.constData(), size_t(u.dataSize));
+                memcpy(bufD->ubuf + u.offset, u.data.constData(), size_t(u.data.size()));
             } else {
                 trackedBufferBarrier(cbD, bufD, QGles2Buffer::AccessUpdate);
                 QGles2CommandBuffer::Command cmd;
@@ -1722,8 +1722,8 @@ void QRhiGles2::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
                 cmd.args.bufferSubData.target = bufD->targetForDataOps;
                 cmd.args.bufferSubData.buffer = bufD->buffer;
                 cmd.args.bufferSubData.offset = u.offset;
-                cmd.args.bufferSubData.size = u.dataSize;
-                cmd.args.bufferSubData.data = cbD->retainData(u.data);
+                cmd.args.bufferSubData.size = u.data.size();
+                cmd.args.bufferSubData.data = cbD->retainBufferData(u.data);
                 cbD->commands.append(cmd);
             }
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::Read) {
diff --git a/src/gui/rhi/qrhigles2_p_p.h b/src/gui/rhi/qrhigles2_p_p.h
index 5940633151..65fb820a36 100644
--- a/src/gui/rhi/qrhigles2_p_p.h
+++ b/src/gui/rhi/qrhigles2_p_p.h
@@ -578,6 +578,7 @@ struct QGles2CommandBuffer : public QRhiCommandBuffer
     } computePassState;
 
     QVarLengthArray<QByteArray, 4> dataRetainPool;
+    QVarLengthArray<QRhiBufferData, 4> bufferDataRetainPool;
     QVarLengthArray<QImage, 4> imageRetainPool;
 
     // relies heavily on implicit sharing (no copies of the actual data will be made)
@@ -585,6 +586,10 @@ struct QGles2CommandBuffer : public QRhiCommandBuffer
         dataRetainPool.append(data);
         return dataRetainPool.last().constData();
     }
+    const uchar *retainBufferData(const QRhiBufferData &data) {
+        bufferDataRetainPool.append(data);
+        return reinterpret_cast<const uchar *>(bufferDataRetainPool.last().constData());
+    }
     const void *retainImage(const QImage &image) {
         imageRetainPool.append(image);
         return imageRetainPool.last().constBits();
@@ -592,6 +597,7 @@ struct QGles2CommandBuffer : public QRhiCommandBuffer
     void resetCommands() {
         commands.clear();
         dataRetainPool.clear();
+        bufferDataRetainPool.clear();
         imageRetainPool.clear();
 
         passResTrackers.clear();
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index 9058a7556a..a31d37c01a 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -1703,10 +1703,10 @@ void QRhiMetal::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
             // basically the same. So go through the same pendingUpdates machinery.
             QMetalBuffer *bufD = QRHI_RES(QMetalBuffer, u.buf);
             Q_ASSERT(bufD->m_type != QRhiBuffer::Dynamic);
-            Q_ASSERT(u.offset + u.dataSize <= bufD->m_size);
+            Q_ASSERT(u.offset + u.data.size() <= bufD->m_size);
             for (int i = 0, ie = bufD->d->slotted ? QMTL_FRAMES_IN_FLIGHT : 1; i != ie; ++i)
                 bufD->d->pendingUpdates[i].append(
-                            QRhiResourceUpdateBatchPrivate::BufferOp::dynamicUpdate(u.buf, u.offset, u.dataSize, u.data.constData()));
+                            QRhiResourceUpdateBatchPrivate::BufferOp::dynamicUpdate(u.buf, u.offset, u.data.size(), u.data.constData()));
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::Read) {
             QMetalBuffer *bufD = QRHI_RES(QMetalBuffer, u.buf);
             executeBufferHostWritesForCurrentFrame(bufD);
@@ -1868,11 +1868,11 @@ void QRhiMetal::executeBufferHostWritesForSlot(QMetalBuffer *bufD, int slot)
     int changeEnd = -1;
     for (const QRhiResourceUpdateBatchPrivate::BufferOp &u : qAsConst(bufD->d->pendingUpdates[slot])) {
         Q_ASSERT(bufD == QRHI_RES(QMetalBuffer, u.buf));
-        memcpy(static_cast<char *>(p) + u.offset, u.data.constData(), size_t(u.dataSize));
+        memcpy(static_cast<char *>(p) + u.offset, u.data.constData(), size_t(u.data.size()));
         if (changeBegin == -1 || u.offset < changeBegin)
             changeBegin = u.offset;
-        if (changeEnd == -1 || u.offset + u.dataSize > changeEnd)
-            changeEnd = u.offset + u.dataSize;
+        if (changeEnd == -1 || u.offset + u.data.size() > changeEnd)
+            changeEnd = u.offset + u.data.size();
     }
 #ifdef Q_OS_MACOS
     if (changeBegin >= 0 && bufD->d->managed)
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index e0eb110c0d..4c650e68a0 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -465,7 +465,7 @@ void QRhiNull::resourceUpdate(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *re
                 || u.type == QRhiResourceUpdateBatchPrivate::BufferOp::StaticUpload)
         {
             QNullBuffer *bufD = QRHI_RES(QNullBuffer, u.buf);
-            memcpy(bufD->data.data() + u.offset, u.data.constData(), size_t(u.dataSize));
+            memcpy(bufD->data.data() + u.offset, u.data.constData(), size_t(u.data.size()));
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::Read) {
             QRhiBufferReadbackResult *result = u.result;
             result->data.resize(u.readSize);
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 5146a2ccc3..c0162820b6 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -2929,11 +2929,11 @@ void QRhiVulkan::enqueueResourceUpdates(QVkCommandBuffer *cbD, QRhiResourceUpdat
             QVkBuffer *bufD = QRHI_RES(QVkBuffer, u.buf);
             Q_ASSERT(bufD->m_type == QRhiBuffer::Dynamic);
             for (int i = 0; i < QVK_FRAMES_IN_FLIGHT; ++i)
-                bufD->pendingDynamicUpdates[i].append({ u.offset, u.dataSize, u.data });
+                bufD->pendingDynamicUpdates[i].append({ u.offset, u.data });
         } else if (u.type == QRhiResourceUpdateBatchPrivate::BufferOp::StaticUpload) {
             QVkBuffer *bufD = QRHI_RES(QVkBuffer, u.buf);
             Q_ASSERT(bufD->m_type != QRhiBuffer::Dynamic);
-            Q_ASSERT(u.offset + u.dataSize <= bufD->m_size);
+            Q_ASSERT(u.offset + u.data.size() <= bufD->m_size);
 
             if (!bufD->stagingBuffers[currentFrameSlot]) {
                 VkBufferCreateInfo bufferInfo;
@@ -2967,9 +2967,9 @@ void QRhiVulkan::enqueueResourceUpdates(QVkCommandBuffer *cbD, QRhiResourceUpdat
                 qWarning("Failed to map buffer: %d", err);
                 continue;
             }
-            memcpy(static_cast<uchar *>(p) + u.offset, u.data.constData(), size_t(u.dataSize));
+            memcpy(static_cast<uchar *>(p) + u.offset, u.data.constData(), size_t(u.data.size()));
             vmaUnmapMemory(toVmaAllocator(allocator), a);
-            vmaFlushAllocation(toVmaAllocator(allocator), a, VkDeviceSize(u.offset), VkDeviceSize(u.dataSize));
+            vmaFlushAllocation(toVmaAllocator(allocator), a, VkDeviceSize(u.offset), VkDeviceSize(u.data.size()));
 
             trackedBufferBarrier(cbD, bufD, 0,
                                  VK_ACCESS_TRANSFER_WRITE_BIT, VK_PIPELINE_STAGE_TRANSFER_BIT);
@@ -2978,7 +2978,7 @@ void QRhiVulkan::enqueueResourceUpdates(QVkCommandBuffer *cbD, QRhiResourceUpdat
             memset(&copyInfo, 0, sizeof(copyInfo));
             copyInfo.srcOffset = VkDeviceSize(u.offset);
             copyInfo.dstOffset = VkDeviceSize(u.offset);
-            copyInfo.size = VkDeviceSize(u.dataSize);
+            copyInfo.size = VkDeviceSize(u.data.size());
 
             QVkCommandBuffer::Command cmd;
             cmd.cmd = QVkCommandBuffer::Command::CopyBuffer;
@@ -3429,11 +3429,11 @@ void QRhiVulkan::executeBufferHostWritesForSlot(QVkBuffer *bufD, int slot)
     int changeBegin = -1;
     int changeEnd = -1;
     for (const QVkBuffer::DynamicUpdate &u : qAsConst(bufD->pendingDynamicUpdates[slot])) {
-        memcpy(static_cast<char *>(p) + u.offset, u.data.constData(), size_t(u.size));
+        memcpy(static_cast<char *>(p) + u.offset, u.data.constData(), size_t(u.data.size()));
         if (changeBegin == -1 || u.offset < changeBegin)
             changeBegin = u.offset;
-        if (changeEnd == -1 || u.offset + u.size > changeEnd)
-            changeEnd = u.offset + u.size;
+        if (changeEnd == -1 || u.offset + u.data.size() > changeEnd)
+            changeEnd = u.offset + u.data.size();
     }
     vmaUnmapMemory(toVmaAllocator(allocator), a);
     if (changeBegin >= 0)
diff --git a/src/gui/rhi/qrhivulkan_p_p.h b/src/gui/rhi/qrhivulkan_p_p.h
index f3157c9112..c590039bc1 100644
--- a/src/gui/rhi/qrhivulkan_p_p.h
+++ b/src/gui/rhi/qrhivulkan_p_p.h
@@ -82,8 +82,7 @@ struct QVkBuffer : public QRhiBuffer
     QVkAlloc allocations[QVK_FRAMES_IN_FLIGHT];
     struct DynamicUpdate {
         int offset;
-        int size;
-        QByteArray data;
+        QRhiBufferData data;
     };
     QVarLengthArray<DynamicUpdate, 16> pendingDynamicUpdates[QVK_FRAMES_IN_FLIGHT];
     VkBuffer stagingBuffers[QVK_FRAMES_IN_FLIGHT];
@@ -98,6 +97,8 @@ struct QVkBuffer : public QRhiBuffer
     friend class QRhiVulkan;
 };
 
+Q_DECLARE_TYPEINFO(QVkBuffer::DynamicUpdate, Q_MOVABLE_TYPE);
+
 struct QVkTexture;
 
 struct QVkRenderBuffer : public QRhiRenderBuffer