[dxvk] Use linked list for CS chunks

Improves memory efficiency and CPU overhead of the CSMT implementation
when the average number of bytes per command entry is less than 64 bytes.

src/dxvk/dxvk_cs.cpp

@@ -8,19 +8,31 @@ namespace dxvk {
   
   
   DxvkCsChunk::~DxvkCsChunk() {
-    for (size_t i = 0; i < m_commandCount; i++)
+    auto cmd = m_head;
-      m_commandList[i]->~DxvkCsCmd();
+    
+    while (cmd != nullptr) {
+      auto next = cmd->next();
+      cmd->~DxvkCsCmd();
+      cmd = next;
+    }
   }
   
   
   void DxvkCsChunk::executeAll(DxvkContext* ctx) {
-    for (size_t i = 0; i < m_commandCount; i++) {
+    auto cmd = m_head;
-      m_commandList[i]->exec(ctx);
+    
-      m_commandList[i]->~DxvkCsCmd();
+    while (cmd != nullptr) {
+      auto next = cmd->next();
+      cmd->exec(ctx);
+      cmd->~DxvkCsCmd();
+      cmd = next;
     }
     
     m_commandCount  = 0;
     m_commandOffset = 0;
+    
+    m_head = nullptr;
+    m_tail = nullptr;
   }
   
   

src/dxvk/dxvk_cs.h

@@ -22,12 +22,35 @@ namespace dxvk {
     
     virtual ~DxvkCsCmd() { }
     
+    /**
+     * \brief Retrieves next command in a command chain
+     * 
+     * This can be used to quickly iterate
+     * over commands within a chunk.
+     * \returns Pointer the next command
+     */
+    DxvkCsCmd* next() const {
+      return m_next;
+    }
+    
+    /**
+     * \brief Sets next command in a command chain
+     * \param [in] next Next command
+     */
+    void setNext(DxvkCsCmd* next) {
+      m_next = next;
+    }
+    
     /**
      * \brief Executes embedded commands
      * \param [in] ctx The target context
      */
     virtual void exec(DxvkContext* ctx) const = 0;
     
+  private:
+    
+    DxvkCsCmd* m_next = nullptr;
+    
   };
   
   
@@ -65,8 +88,7 @@ namespace dxvk {
    * Stores a list of commands.
    */
   class DxvkCsChunk : public RcObject {
-    constexpr static size_t MaxCommands  = 1024;
+    constexpr static size_t MaxBlockSize = 65536;
-    constexpr static size_t MaxBlockSize = 64 * MaxCommands;
   public:
     
     DxvkCsChunk();
@@ -96,13 +118,18 @@ namespace dxvk {
     bool push(T& command) {
       using FuncType = DxvkCsTypedCmd<T>;
       
-      if (m_commandCount >= MaxCommands
+      if (m_commandOffset + sizeof(FuncType) > MaxBlockSize)
-       || m_commandOffset + sizeof(FuncType) > MaxBlockSize)
         return false;
       
-      m_commandList[m_commandCount] =
+      DxvkCsCmd* tail = m_tail;
-        new (m_data + m_commandOffset)
+      
-          FuncType(std::move(command));
+      m_tail = new (m_data + m_commandOffset)
+        FuncType(std::move(command));
+      
+      if (tail != nullptr)
+        tail->setNext(m_tail);
+      else
+        m_head = m_tail;
       
       m_commandCount  += 1;
       m_commandOffset += sizeof(FuncType);
@@ -123,7 +150,8 @@ namespace dxvk {
     size_t m_commandCount  = 0;
     size_t m_commandOffset = 0;
     
-    std::array<DxvkCsCmd*, MaxCommands> m_commandList;
+    DxvkCsCmd* m_head = nullptr;
+    DxvkCsCmd* m_tail = nullptr;
     
     alignas(64)
     char m_data[MaxBlockSize];