fix: fix login wallpaper startup delay

programs/lib/libc/libc.c

@@ -99,6 +99,7 @@ static inline long _mtk_syscall4(long nr, long a1, long a2, long a3, long a4) {
 #define SYS_CLOSE   9
 #define SYS_READDIR 10
 #define SYS_ALLOC   11
+#define SYS_ALLOC_EAGER 187
 #define SYS_FREE    12
 #define SYS_GETMILLISECONDS 14
 #define SYS_GETCHAR 18
@@ -679,6 +680,14 @@ int tolower(int c)  { return (c >= 'A' && c <= 'Z') ? c + 32 : c; }
 #define HEAP_ALIGN  16ULL
 #define DIRECT_THRESHOLD (256ULL * 1024ULL)
 
+/* A direct mapping is one object the caller sized itself, so it is nearly
+   always written end to end (an image buffer, a loaded file). Committing it
+   up front replaces one page fault, one kernel mutex acquire and one VMA walk
+   per 4 KiB with a single loop -- thousands of traps for a decoded image.
+   Beyond the cap, stay lazy: a very large mapping is more likely to be a
+   sparsely touched reservation, and eager commit would pin the lot. */
+#define EAGER_DIRECT_LIMIT (32ULL * 1024ULL * 1024ULL)
+
 struct HeapHeader {
     uint64_t magic;
     uint64_t requested_size;
@@ -855,8 +864,10 @@ static void *heap_malloc_locked(size_t size) {
     if (needed >= DIRECT_THRESHOLD) {
         if (needed > UINT64_MAX - 0xFFFULL) return NULL;
         uint64_t mapping_size = (needed + 0xFFFULL) & ~0xFFFULL;
+        long alloc_nr = (mapping_size <= EAGER_DIRECT_LIMIT)
+                        ? SYS_ALLOC_EAGER : SYS_ALLOC;
         struct HeapHeader *hdr = (struct HeapHeader *)
-            _mtk_syscall1(SYS_ALLOC, (long)mapping_size);
+            _mtk_syscall1(alloc_nr, (long)mapping_size);
         if (hdr == NULL) return NULL;
         hdr->magic = DIRECT_MAGIC;
         hdr->requested_size = size;