diff --git a/core/sys_config.php b/core/sys_config.php
index 296885a8..7f07e6db 100644
--- a/core/sys_config.php
+++ b/core/sys_config.php
@@ -41,6 +41,7 @@ _d("CORE_EXTS", "bbcode,user,mail,upload,image,view,handle_pixel,ext_manager,set
 _d("EXTRA_EXTS", "");        // string   optional extra extensions
 _d("BASE_URL", null);        // string   force a specific base URL (default is auto-detect)
 _d("MIN_PHP_VERSION", '7.0');// string   minimum supported PHP version
+_d("SLOW_PAGES", null);      // float    log pages which take more time than this
 _d("ENABLED_MODS", "imageboard");
 
 /*
diff --git a/core/util.php b/core/util.php
index 7129f0f2..09b87dab 100644
--- a/core/util.php
+++ b/core/util.php
@@ -350,6 +350,18 @@ function get_debug_info(): string {
 	return $debug;
 }
 
+function log_slow() {
+	global $_shm_load_start;
+	if(!is_null(SLOW_PAGES)) {
+		$_time = microtime(true) - $_shm_load_start;
+		if($_time > SLOW_PAGES) {
+			$_query = _get_query();
+			$_dbg = get_debug_info();
+			file_put_contents("data/slow-pages.log", "$_time $_query $_dbg\n", FILE_APPEND | LOCK_EX);
+		}
+	}
+}
+
 function score_assert_handler($file, $line, $code, $desc = null) {
 	$file = basename($file);
 	print("Assertion failed at $file:$line: $code ($desc)");
diff --git a/index.php b/index.php
index e748c06b..7c9ee6b9 100644
--- a/index.php
+++ b/index.php
@@ -107,4 +107,5 @@ catch(Exception $e) {
 	_fatal_error($e);
 	$_shm_ctx->log_ender();
 }
+log_slow();