pmm: detect and use highest available frame order

After creating early frames, the process_memory_range() finds highest available frame order (i.e. frame order whose size fits into available physical memory size). Instead of creating 2M frames by default, it creates frames of the detected order and uses the rest of available space to create 2M frames and 4K frames. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
KernelTestFramework · Jan 23, 2022 · e55bb28 · e55bb28
1 parent 1be371d
commit e55bb28
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Showing 2 changed files with 20 additions and 12 deletions.
diff --git a/include/mm/pmm.h b/include/mm/pmm.h
@@ -60,6 +60,8 @@ typedef struct frames_array frames_array_t;
 
 typedef bool (*free_frames_cond_t)(frame_t *free_frame);
 
+#define ORDER_TO_SIZE(order) (PAGE_SIZE << (order))
+
 #define FIRST_FRAME_SIBLING(mfn, order) ((mfn) % (1UL << (order)) == 0)
 #define NEXT_MFN(mfn, order)            ((mfn) + (1UL << (order)))
 #define PREV_MFN(mfn, order)            ((mfn) - (1UL << (order)))

diff --git a/mm/pmm.c b/mm/pmm.c
@@ -237,8 +237,18 @@ static inline void add_frame(mfn_t mfn, unsigned int order) {
     list_add_tail(&frame->list, &free_frames[order]);
 }
 
+static inline unsigned int find_max_avail_order(size_t size) {
+    for (unsigned int order = MAX_PAGE_ORDER; order > PAGE_ORDER_4K; order--) {
+        if (ORDER_TO_SIZE(order) <= size)
+            return order;
+    }
+
+    return PAGE_ORDER_4K;
+}
+
 static size_t process_memory_range(unsigned index) {
     paddr_t start, end, cur;
+    unsigned int max_order;
     addr_range_t range;
     size_t size;
 
@@ -261,31 +271,27 @@ static size_t process_memory_range(unsigned index) {
             add_early_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
         else
             add_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
-        cur += (PAGE_SIZE << PAGE_ORDER_4K);
+        cur += ORDER_TO_SIZE(PAGE_ORDER_4K);
     }
 
-    /* Add initial 2M frames and align to 1G. */
-    while (cur % PAGE_SIZE_1G && cur + PAGE_SIZE_2M <= end) {
-        add_frame(paddr_to_mfn(cur), PAGE_ORDER_2M);
-        cur += (PAGE_SIZE << PAGE_ORDER_2M);
-    }
+    max_order = find_max_avail_order(end - cur);
 
-    /* Add all remaining 1G frames. */
-    while (cur + PAGE_SIZE_1G <= end) {
-        add_frame(paddr_to_mfn(cur), PAGE_ORDER_1G);
-        cur += (PAGE_SIZE << PAGE_ORDER_1G);
+    /* Add all available max_order frames. */
+    while (cur + ORDER_TO_SIZE(max_order) <= end) {
+        add_frame(paddr_to_mfn(cur), max_order);
+        cur += ORDER_TO_SIZE(max_order);
     }
 
     /* Add all remaining 2M frames. */
     while (cur + PAGE_SIZE_2M <= end) {
         add_frame(paddr_to_mfn(cur), PAGE_ORDER_2M);
-        cur += (PAGE_SIZE << PAGE_ORDER_2M);
+        cur += ORDER_TO_SIZE(PAGE_ORDER_2M);
     }
 
     /* Add all remaining 4K frames. */
     while (cur < end) {
         add_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
-        cur += (PAGE_SIZE << PAGE_ORDER_4K);
+        cur += ORDER_TO_SIZE(PAGE_ORDER_4K);
     }
 
     if (cur != end) {