Hello all,
While working on one of our projects i stumbled on what i think is a problem in the Zend engine regarding the memory limit code. On some scripts the server reported memexhausts when the site had heavy traffic. I wrote a PHP extension that can return a script's memory usage at any time during execution, to find out what caused these errors. The memory usage extension uses two methods, the first being the total of all allocated persistent and regular memory blocks (REAL_SIZE), the second method is just a return of the variable AG(allocated_memory). Now in one of the scripts i was monitoring i noticed a constant increase in memory usage (using the second method described earlier) of 10KB when constantly reloading in my browser. Using the second method the memory usage was constant. After some investigation i discovered that that particular script leaked 10 KB of memory on every request. I analyzed the memory limit code in Zend, and adapted sapi/apache/mod_php4.c to not only return AG(allocated_memory_peak) as an Apache variable, but also AG(allocated_memory) to check whether AG(allocated_memory) was zero after execution of each script. This was not the case. When a script leaks memory (which really shouldn't happen, but it does), after its execution AG(allocated_memory) still contains the amount of memory that was not de-allocated. This is what seems to cause the trouble. Since AG(allocated_memory) is not always zero after execution of a script, and AG(allocated_memory_peak) is dependant on it, consecutive requests on a leaking script result in an ever increasing AG(allocated_memory) and thus an ever increasing AG(allocated_memory_peak), which at a certain moment results in AG(allocated_memory_peak) > AG(memory_limit). This is what caused the memory exhaust errors. I noticed that AG(allocated_memory_peak) *is* reset after script execution in sapi/apache/mod_php4.c, but AG(allocated_memory) isn't. I should really be tracking down the reason for the script to leak 10 KB of memory, but i fixed this problem temporarily by adding a AG(allocated_memory) = 0 line to mod_php4.c in function send_parsed_php(), though i'm not sure if this is the right thing to do. For now it fixes the memory exhausts. I am interested in hearing your views on this matter. With regards, Hans Rakers -- Hans Rakers ([EMAIL PROTECTED]) Tel: +31 (0)23 5325689 System administrator/Developer Fax: +31 (0)23 5314332 Parse - Postcode.NL - TeKoop.NL http://www.parse.nl/ Haarlem, the Netherlands -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
