The Bitrix platform is written in PHP which implies that the website performance ultimately depends on the PHP interpreter settings. One of the crucial factors is the presence of a PHP precompiler (APC, ZendOptimizer+, eAccelerator, XCache, WinCache).

It is recommended that you set up the precompiler administration page which will allow you to see the runtime parameters and edit them if so required, for example: set the adequate cache size, track redundant files etc. Also pay attention to such PHP parameters as "open_basedir" and "realpath_cache_size".

1. Open "Settings > Performance > Performance Panel", select the "Configuration" tab. The "PHP Configuration" row should show "optimum" in the "Score" column. Otherwise, you have to apply more effort to PHP configuration.
2. Ensure there is sufficient memory allocated for the PHP interpreter. To do so, enable PHP error logging and perform a stress test (or any other kind of test you find appropriate to track memory consumption). Once the test is done, search the log file for memory related errors. If such errors exist, increase the value of the "memory_limit" parameter. However, if a web page or script requires too much memory to run (128 MB or more), it requires some correction, optimization or even complete redesign.