From 288b2f8b248afab372240954c2d0f82417b50cd1 Mon Sep 17 00:00:00 2001
From: Aiken Harris <harraiken91@gmail.com>
Date: Tue, 23 Dec 2025 14:27:12 +0100
Subject: [PATCH] Introduce page coloring support to memory manager

---
 xtoskrnl/includes/mm.hh        |  1 +
 xtoskrnl/includes/mm/colors.hh | 35 +++++++++++++
 xtoskrnl/mm/colors.cc          | 95 ++++++++++++++++++++++++++++++++++
 xtoskrnl/mm/data.cc            |  9 ++++
 xtoskrnl/mm/mmgr.cc            |  3 ++
 5 files changed, 143 insertions(+)
 create mode 100644 xtoskrnl/includes/mm/colors.hh
 create mode 100644 xtoskrnl/mm/colors.cc

diff --git a/xtoskrnl/includes/mm.hh b/xtoskrnl/includes/mm.hh
index bd94683e..b34863dc 100644
--- a/xtoskrnl/includes/mm.hh
+++ b/xtoskrnl/includes/mm.hh
@@ -15,6 +15,7 @@
 #include XTOS_ARCH_HEADER(mm, paging.hh)
 #include XTOS_ARCH_HEADER(mm, pte.hh)
 
+#include <mm/colors.hh>
 #include <mm/hlpool.hh>
 #include <mm/kpool.hh>
 #include <mm/mmgr.hh>
diff --git a/xtoskrnl/includes/mm/colors.hh b/xtoskrnl/includes/mm/colors.hh
new file mode 100644
index 00000000..229b6498
--- /dev/null
+++ b/xtoskrnl/includes/mm/colors.hh
@@ -0,0 +1,35 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtoskrnl/includes/mm/colors.hh
+ * DESCRIPTION:     Memory manager page coloring subsystem
+ * DEVELOPERS:      Aiken Harris <harraiken91@gmail.com>
+ */
+
+#ifndef __XTOSKRNL_MM_COLORS_HH
+#define __XTOSKRNL_MM_COLORS_HH
+
+#include <xtos.hh>
+
+
+/* Memory Manager */
+namespace MM
+{
+    class Colors
+    {
+        private:
+            STATIC PMMCOLOR_TABLES FreePages[FreePageList + 1];
+            STATIC ULONG PagingColors;
+            STATIC ULONG PagingColorsMask;
+
+        public:
+            STATIC XTAPI VOID ComputePageColoring(VOID);
+            STATIC XTAPI PMMCOLOR_TABLES GetFreePages(MMPAGELISTS PageList,
+                                                      ULONG Color);
+            STATIC XTAPI ULONG GetNextColor();
+            STATIC XTAPI ULONG GetPagingColors();
+            STATIC XTAPI ULONG GetPagingColorsMask();
+    };
+}
+
+#endif /* __XTOSKRNL_MM_PFN_HH */
diff --git a/xtoskrnl/mm/colors.cc b/xtoskrnl/mm/colors.cc
new file mode 100644
index 00000000..e2258466
--- /dev/null
+++ b/xtoskrnl/mm/colors.cc
@@ -0,0 +1,95 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtoskrnl/mm/colors.cc
+ * DESCRIPTION:     Memory manager page coloring subsystem
+ * DEVELOPERS:      Aiken Harris <harraiken91@gmail.com>
+ */
+
+#include <xtos.hh>
+
+
+/**
+ * Computes & initializes the system's page coloring.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+VOID
+MM::Colors::ComputePageColoring(VOID)
+{
+    UNIMPLEMENTED;
+
+    /* Compute L2 paging colors and mask */
+    PagingColors = MM_PAGING_COLORS;
+    PagingColorsMask = PagingColors - 1;
+}
+
+/**
+ * Retrieves a pointer to the color table for a specific page list and color.
+ *
+ * @param PageList
+ *        The page list type (e.g., FreePageList, ZeroedPageList).
+ *
+ * @param Color
+ *        Supplies the specific color index.
+ *
+ * @return This routine returns a pointer to the corresponding MMCOLOR_TABLES structure.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+PMMCOLOR_TABLES
+MM::Colors::GetFreePages(MMPAGELISTS PageList,
+                         ULONG Color)
+{
+    /* Return a pointer to the requested color table entry */
+    return &FreePages[PageList][Color];
+}
+
+/**
+ * Retrieves the next available color for page coloring.
+ *
+ * @return This routine returns the next color value, ensuring it stays within the valid color range.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+ULONG
+MM::Colors::GetNextColor()
+{
+    /* Increment the color counter and wrap it around using the mask */
+    return ((++PagingColors) & PagingColorsMask);
+}
+
+/**
+ * Retrieves the total number of page colors configured in the system.
+ *
+ * @return This routine returns the number of page colors.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+ULONG
+MM::Colors::GetPagingColors()
+{
+    /* Return the total number of page colors */
+    return PagingColors;
+}
+
+/**
+ * Retrieves the bitmask used for calculating a page's color.
+ *
+ * @return This routine returns the page color mask.
+ *
+ * @since XT 1.0
+ */
+XTAPI
+ULONG
+MM::Colors::GetPagingColorsMask()
+{
+    /* Return the mask used for page coloring calculations */
+    return PagingColorsMask;
+}
diff --git a/xtoskrnl/mm/data.cc b/xtoskrnl/mm/data.cc
index 296c0d4f..de5fe417 100644
--- a/xtoskrnl/mm/data.cc
+++ b/xtoskrnl/mm/data.cc
@@ -9,6 +9,15 @@
 #include <xtos.hh>
 
 
+/* Array of free page lists segregated by cache color */
+PMMCOLOR_TABLES MM::Colors::FreePages[FreePageList + 1];
+
+/* Number of supported page colors */
+ULONG MM::Colors::PagingColors;
+
+/* Bitmask used to calculate the cache color index */
+ULONG MM::Colors::PagingColorsMask;
+
 /* Allocation descriptors dedicated for hardware layer */
 LOADER_MEMORY_DESCRIPTOR MM::HardwarePool::HardwareAllocationDescriptors[MM_HARDWARE_ALLOCATION_DESCRIPTORS];
 
diff --git a/xtoskrnl/mm/mmgr.cc b/xtoskrnl/mm/mmgr.cc
index 5aa17ed2..c305c04e 100644
--- a/xtoskrnl/mm/mmgr.cc
+++ b/xtoskrnl/mm/mmgr.cc
@@ -54,6 +54,9 @@ MM::Manager::InitializeMemoryManager(VOID)
         KE::Crash::Panic(0);
     }
 
+    /* Compute page colors to reduce CPU cache conflicts */
+    MM::Colors::ComputePageColoring();
+
     /* Compute allocation size for the PFN database */
     MM::Pfn::ComputePfnDatabaseSize();