Optimize malloc with hybrid allocation strategy

This commit implements hybrid allocation approach to balance speed and
memory efficiency:
- First-fit for small allocations (≤64 bytes) for speed optimization
- Best-fit for large allocations (>64 bytes) for memory efficiency
- Early exit optimization on perfect matches in best-fit search

Author: jserv

lib/c.c

@@ -636,19 +636,36 @@ void *malloc(int size)
         __freelist_head->size = -1;
     }
 
-    /* Search for the best fit chunk in the free list */
+    /* Hybrid allocation strategy: first-fit for small, best-fit for large */
     chunk_t *best_fit_chunk = NULL;
     chunk_t *allocated;
     int best_size = 0;
 
     if (!__freelist_head->next) {
         allocated = NULL;
     } else {
-        for (chunk_t *fh = __freelist_head; fh->next; fh = fh->next) {
-            int fh_size = CHUNK_GET_SIZE(fh->size);
-            if (fh_size >= size && (!best_fit_chunk || fh_size < best_size)) {
-                best_fit_chunk = fh;
-                best_size = fh_size;
+        if (size <= 64) {
+            /* First-fit for small allocations (speed optimization) */
+            for (chunk_t *fh = __freelist_head; fh->next; fh = fh->next) {
+                int fh_size = CHUNK_GET_SIZE(fh->size);
+                if (fh_size >= size) {
+                    best_fit_chunk = fh;
+                    best_size = fh_size;
+                    break; /* Take first suitable chunk */
+                }
+            }
+        } else {
+            /* Best-fit for large allocations (memory efficiency) */
+            for (chunk_t *fh = __freelist_head; fh->next; fh = fh->next) {
+                int fh_size = CHUNK_GET_SIZE(fh->size);
+                if (fh_size >= size &&
+                    (!best_fit_chunk || fh_size < best_size)) {
+                    best_fit_chunk = fh;
+                    best_size = fh_size;
+                    /* Early exit on perfect match to avoid useless scanning */
+                    if (best_size == size)
+                        break;
+                }
             }
         }
 
@@ -771,7 +788,7 @@ void free(void *ptr)
         __alloc_tail = prev;
     }
 
-    /* Insert head in __freelist_head */
+    /* Insert at head of freelist */
     cur->next = __freelist_head;
     cur->prev = NULL;
     chunk_set_freed(cur);