TYPO3 Core

This function checks for every activated extension if ext_typoscript_constants.txt, ext_typoscript_constants.typoscript, ext_typoscript_setup.txt and ext_typoscript_setup.typoscript exists. If an installation have many extensions, this generates a lot of I/O. My question: It is possible to change this function to make this file checks only if this files are registered in the extension (e.g. in ext_localconf.php)?

If you want to add PageTSConfig, you must also register the file in ext_localconf.php.

\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPageTSConfig(
'@import "EXT:your_ext_key/Configuration/TSConfig/tsconfig.tsconfig"'
);

Maybe the location of this files should be in 'Configuration/TypoScript/'. This brings the TypoScript definitions together at one location and clean up the root extension directory.

An other option could be to cache this files like it is done for ext_tables.php as well as ext_localconf.php.