opcache posix creating special shared segments for FreeBSD 13 and above.

From this release, it is permitted to create shared memory blocks tagged
 as large for faster accesses for a size compatible with otherwise
we fallback to a classic creation.

Author: devnexen

ext/opcache/config.m4

@@ -105,7 +105,7 @@ if test "$PHP_OPCACHE" != "no"; then
 
   fi
 
-  AC_CHECK_FUNCS([mprotect])
+  AC_CHECK_FUNCS([mprotect shm_create_largepage])
 
   AC_MSG_CHECKING(for sysvipc shared memory support)
   AC_RUN_IFELSE([AC_LANG_SOURCE([[

ext/opcache/shared_alloc_posix.c

@@ -40,6 +40,31 @@ static int create_segments(size_t requested_size, zend_shared_segment_posix ***s
 {
 	zend_shared_segment_posix *shared_segment;
 	char shared_segment_name[sizeof("/ZendAccelerator.") + 20];
+	int shared_segment_flags = O_RDWR|O_CREAT|O_TRUNC;
+	mode_t shared_segment_mode = 0600;
+
+#if defined(HAVE_SHM_CREATE_LARGEPAGE)
+	/**
+	 * architectures have 3 entries max and we are interested
+	 * from the second offset minimum to be worthy creating
+	 * a special shared segment tagged as 'large'.
+	 * only then amd64/i386/arm64 and perharps risc64*
+	 * archs are on interest here.
+	 */
+	size_t i, shared_segment_lg_index = 0;
+	static size_t pgindexes[3] = {0};
+	static size_t pgentries = sizeof(pgindexes) / sizeof(pgindexes[0]);
+
+	if (pgindexes[0] == 0)
+		getpagesizes(pgindexes, pgentries);
+
+	for (i = 1; i < pgentries; i ++) {
+		if (!(requested_size % pgindexes[i])) {
+			shared_segment_lg_index = i;
+			break;
+		}
+	}
+#endif
 
 	*shared_segments_count = 1;
 	*shared_segments_p = (zend_shared_segment_posix **) calloc(1, sizeof(zend_shared_segment_posix) + sizeof(void *));
@@ -51,7 +76,12 @@ static int create_segments(size_t requested_size, zend_shared_segment_posix ***s
 	(*shared_segments_p)[0] = shared_segment;
 
 	sprintf(shared_segment_name, "/ZendAccelerator.%d", getpid());
-	shared_segment->shm_fd = shm_open(shared_segment_name, O_RDWR|O_CREAT|O_TRUNC, 0600);
+	shared_segment->shm_fd = 
+#if defined(HAVE_SHM_CREATE_LARGEPAGE)
+                shared_segment_lg_index > 0 ?
+                shm_create_largepage(shared_segment_name, shared_segment_flags, shared_segment_lg_index, SHM_LARGEPAGE_ALLOC_DEFAULT, shared_segment_mode) :
+#endif
+	        shm_open(shared_segment_name, shared_segment_flags, shared_segment_mode);
 	if (shared_segment->shm_fd == -1) {
 		*error_in = "shm_open";
 		return ALLOC_FAILURE;