diff --git a/src/arena.c b/src/arena.c
index aac70a2..1deddf4 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -3,10 +3,10 @@
 #include "platform.h"
 
 
-MemoryBlock *memoryblock_allocate(size_t size, size_t commit_size)
+MemoryBlock *memoryblock_allocate(U32 size, U32 commit_size)
 {
-    size_t aligned_size        = AlignToPageEnd(size);
-    size_t aligned_commit_size = AlignToPageEnd(commit_size);
+    size_t aligned_size        = AlignUpToPage(size);
+    size_t aligned_commit_size = AlignUpToPage(commit_size);
 
     MemoryBlock *block = memory_reserve(aligned_size);
     Assert(block != NULL);
@@ -27,6 +27,8 @@ void arena_init(Arena *arena, const ArenaParams *params)
     Assert(params->size > MemoryBlock_Header_Size);
     Assert(params->size < (U32_Max -  platform_page_size())); // Reserving last piece so our math doesn't overflow
     Assert(params->commit_size > 0);
+    Assert(params->commit_size <= params->size);
+
 
     MemoryBlock *block = memoryblock_allocate(params->size, params->commit_size);
     ASAN_UNPOISON_MEMORY_REGION(block, MemoryBlock_Header_Size);
@@ -43,12 +45,13 @@ void arena_init(Arena *arena, const ArenaParams *params)
 void arena_free(Arena *arena)
 {
     MemoryBlock *block = arena->current;
-
+    Assert(arena->checkpoint_level == 0);
     while (block != NULL) {
         MemoryBlock *prev = block->prev;
         memory_free(block->base, block->size);
         block = prev;
     }
+    arena->current = NULL;
 }
 
 void *arena_push(Arena *arena, U32 size, U32 align)
@@ -69,6 +72,8 @@ void *arena_push(Arena *arena, U32 size, U32 align)
         }
 
         MemoryBlock *new_block  = memoryblock_allocate(block_size, new_commit_size);
+        // base_pos tracks the virtual absolute position within an arena
+        // This is not a contiguous space, we use it to free blocks when popping the arena
         new_block->base_pos     = block->base_pos + block->size;
         new_block->prev         = block;
         arena->current          = new_block;
@@ -82,9 +87,9 @@ void *arena_push(Arena *arena, U32 size, U32 align)
     U8 *mem = &block->base[start_pos];
     if (block->committed_pos < end_pos) {
         // Commit more memory
-        U32 aligned_end_pos   = AlignToPageEnd(start_pos + size);
+        U32 aligned_end_pos   = AlignUpToPage(start_pos + size);
         U32 aligned_size      = RoundUpToMultiple(aligned_end_pos - block->committed_pos, arena->commit_size);
-        aligned_size = Min(aligned_size, block->size - block->committed_pos); // Note(nos): Is this actually right ?
+        aligned_size = Min(aligned_size, block->size - block->committed_pos);
 
         memory_commit(&block->base[block->committed_pos], aligned_size);
         block->committed_pos  += aligned_size;
@@ -120,9 +125,9 @@ void arena_pop_to(Arena *arena, U32 abs_pos)
     }
 }
 
-ArenaCheckPoint arena_temp_begin(Arena *arena)
+ArenaCheckpoint arena_temp_begin(Arena *arena)
 {
-    ArenaCheckPoint checkpoint = {};
+    ArenaCheckpoint checkpoint = {};
     checkpoint.arena           = arena;
     checkpoint.absolute_pos    = arena_used(arena);
     arena->checkpoint_level++;
@@ -130,7 +135,7 @@ ArenaCheckPoint arena_temp_begin(Arena *arena)
     return checkpoint;
 }
 
-void arena_temp_end(ArenaCheckPoint *checkpoint)
+void arena_temp_end(ArenaCheckpoint *checkpoint)
 {
     Arena *arena = checkpoint->arena;
     Assert(arena->checkpoint_level > 0);
diff --git a/src/arena.h b/src/arena.h
index 9e9e971..b7e2702 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -2,7 +2,7 @@
 #include "base_core.h"
 
 
-typedef U32 ArenaFlags; // no flags defined yets
+typedef U32 ArenaFlags; // no flags defined yet
 
 typedef struct ArenaParams ArenaParams;
 struct ArenaParams {
@@ -31,8 +31,8 @@ struct Arena {
     S32 checkpoint_level;
 };
 
-typedef struct ArenaCheckPoint ArenaCheckPoint;
-struct ArenaCheckPoint {
+typedef struct ArenaCheckpoint ArenaCheckpoint;
+struct ArenaCheckpoint {
     Arena *arena;
     U32 absolute_pos;
 };
@@ -47,11 +47,11 @@ void *arena_push(Arena *arena, U32 size, U32 align);
 #define arena_push_type(arena, type) arena_push(arena, (U32)sizeof(type), alignof(type))
 #define arena_push_array_of(arena, type, len) arena_push(arena, (U32) (sizeof(type) * (len)), alignof(type))
 
-ArenaCheckPoint arena_temp_begin(Arena *arena);
-void arena_temp_end(ArenaCheckPoint *checkpoint);
+ArenaCheckpoint arena_temp_begin(Arena *arena);
+void arena_temp_end(ArenaCheckpoint *checkpoint);
 void arena_pop_to(Arena *arena, U32 abs_pos);
 void arena_reset(Arena *arena);
-MemoryBlock *memoryblock_allocate(size_t size, size_t commit_size);
+MemoryBlock *memoryblock_allocate(U32 size, U32 commit_size);
 
 
 static INLINE U32 memoryblock_available(const MemoryBlock *block)
diff --git a/src/base_core.h b/src/base_core.h
index dd28138..f640ac6 100644
--- a/src/base_core.h
+++ b/src/base_core.h
@@ -41,10 +41,11 @@ typedef unsigned __int128 U128;
 #define U32_Max     ((U32)0xffffffff)
 #define U64_Max     ((U64)0xffffffffffffffffULL)
 
-#define  U8_Min     ((U8) 0x80)
-#define U16_Min     ((U16)0x8000)
-#define U32_Min     ((U32)0x80000000)
-#define U64_Min     ((U64)0x8000000000000000ULL)
+// Duh ..
+#define  U8_Min     ((U8)0x0)
+#define U16_Min     ((U16)0x0)
+#define U32_Min     ((U32)0x0)
+#define U64_Min     ((U64)0x0)
 
 #define  S8_Max     ((S8) 0x7f)
 #define S16_Max     ((S16)0x7fff)
@@ -163,7 +164,7 @@ typedef unsigned __int128 U128;
  * @param y denominator
  * @return x rounded down nearest multiple of y
  */
-#define RounDownToMultiple(x, y) ((x) / (y) * (y))
+#define RoundDownToMultiple(x, y) ((x) / (y) * (y))
 #define Clamp(val, min, max) (((val) < (min)) ? (min) : ((val) > (max)) ? (max) : (val))
 
 #ifdef __GNUC__
diff --git a/src/main.c b/src/main.c
index dfdbb9d..e3cd66f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -65,7 +65,7 @@ static void arena_test_2(void)
     printf("Allocated ptr %p\n", ptr);
 
     arena_dump(&arena);
-    ArenaCheckPoint checkpoint = arena_temp_begin(&arena);
+    ArenaCheckpoint checkpoint = arena_temp_begin(&arena);
     ptr = arena_push(&arena, MB(2), 8);
     MemoryZero(ptr, MB(2));
 
@@ -74,7 +74,7 @@ static void arena_test_2(void)
     ptr = arena_push(&arena, commit_size , 8);
     MemoryZero(ptr, commit_size  );
 
-    ArenaCheckPoint checkpoint2 = arena_temp_begin(&arena);
+    ArenaCheckpoint checkpoint2 = arena_temp_begin(&arena);
     ptr = arena_push(&arena, 64, 8);
     MemoryZero(ptr, 64);
 
diff --git a/src/platform.c b/src/platform.c
index 654fe05..33ff5e2 100644
--- a/src/platform.c
+++ b/src/platform.c
@@ -13,7 +13,6 @@ U32 platform_page_size(void)
     return getpagesize();
 }
 
-
 void *platform_malloc(size_t size)
 {
     return malloc(size);
@@ -24,16 +23,22 @@ void platform_free(void *mem)
     free(mem);
 }
 
-
-void *memory_allocate(size_t size)
+void *memory_allocate_and_commit(size_t size)
 {
-    Assert(IsPow2(size));
+    Assert(IsPageAligned(size));
 
     void *mem = mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS  | MAP_PRIVATE, -1, 0);
     TRACEF("memory_allocate size=%7zu mem=%p\n", size, mem);
     if (mem == MAP_FAILED) {
         mem = NULL;
+    } else {
+        int rc = madvise(mem, size, MADV_POPULATE_WRITE);
+        if (rc != 0) {
+            munmap(mem, size);
+            mem = NULL;
+        }
     }
+
     return mem;
 }
 
diff --git a/src/platform.h b/src/platform.h
index 8cc3d4e..f0da76e 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -4,7 +4,7 @@
 void *platform_malloc(size_t size);
 U32 platform_page_size(void);
 
-void *memory_allocate(size_t size);
+void *memory_allocate_and_commit(size_t size);
 void *memory_reserve(size_t size);
 void memory_commit(void *mem, size_t size);
 void memory_decommit(void *mem, size_t size);
@@ -12,7 +12,7 @@ void memory_decommit(void *mem, size_t size);
 void memory_free(void *mem, size_t size);
 
 
-static INLINE size_t AlignToPageEnd(size_t value)
+static INLINE size_t AlignUpToPage(size_t value)
 {
     U32 page_size = platform_page_size();
     size_t aligned_value = AlignUpPow2(value, page_size);
@@ -20,7 +20,7 @@ static INLINE size_t AlignToPageEnd(size_t value)
     return aligned_value;
 }
 
-static INLINE size_t AlignToPageStart(size_t value)
+static INLINE size_t AlignDownToPage(size_t value)
 {
     U32 page_size = platform_page_size();
     size_t aligned_value= AlignDownPow2(value, page_size);