1 files changed, 23 insertions, 0 deletions
diff --git a/src/common/host_memory.h b/src/common/host_memory.h
index 8747a1850f..84315091c5 100644
--- a/src/common/host_memory.h
+++ b/src/common/host_memory.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <memory>
 #include <optional>
 #include "common/common_funcs.h"
@@ -52,8 +53,24 @@ public:
 
     void EnableDirectMappedAddress();
 
+    /// Clears guest memory being handed out. Memory still zero since it was created (or since its
+    /// last full clear) is skipped: clearing it only made the host give every page real memory.
     void ClearBackingRegion(size_t physical_offset, size_t length, u32 fill_value);
 
+    /// Memory written once and read again rarely: its pages leave the working set (backing and,
+    /// when given, its view at virtual_offset), so the OS compresses or pages them out first when
+    /// it needs RAM. The contents stay; using the pages brings them back.
+    void HintCold(size_t physical_offset, size_t length,
+                  std::optional<size_t> virtual_offset) const;
+    /// Pages the kernel hands out (cleared or not).
+    void MarkUsed(size_t physical_offset, size_t length);
+
+    /// Pages given back to the kernel: their contents are no longer known to be zero.
+    void MarkDirty(size_t physical_offset, size_t length);
+
+    /// A new kernel on this memory: everything a previous one used may hold data.
+    void ForgetContents();
+
     [[nodiscard]] u8* BackingBasePointer() noexcept {
         return backing_base;
     }
@@ -88,6 +105,12 @@ private:
     u8* backing_base{};
     u8* virtual_base{};
     size_t virtual_base_offset{};
+
+    static constexpr size_t GranuleShift = 16; ///< 64 KiB of backing per state byte
+    static constexpr u8 GranuleUsed = 1 << 0;   ///< Handed out at least once
+    static constexpr u8 GranuleDirty = 1 << 1;  ///< May hold non-zero data
+    std::unique_ptr<std::atomic<u8>[]> granules;
+    size_t num_granules{};
     // Windows requires it for kernels whom lack proper support for some functions!
     bool fallback_buffer{false};
 };