I am not a coder.  I'm not even any good at server maintenance.  But SMW is taking my site down several times a day now.  My wiki is either the biggest, or nearly the biggest SMW wiki (according to with 250,000 pages.  My site runs out of memory and chokes all the time.  I looked in /var/log/messages and it is full of things like

httpd: PHP Fatal error:  Out of memory (allocated 10747904) (tried to allocate 4864 bytes) in /home/reformedword/public_html/includes/AutoLoader.php on line 582

but the php file in question is different every time.  I'm getting one of these kind of errors every half hour or more.
Before you say, "Up your PHP memory", know that I did!  I went up from 64MB to 128MB to 256MB.  Same story.  So I switched to babysitting "top -cd2".  When I change a page without semantic data, HTTPD and MYSQLD requests come, linger and go.  But when I change a page with Semantic::Values, the HTTPD and MYSQLD processes take a VERY long time to die, sometimes never.  Eventually the site runs out of memory.

Like I said, php.ini has 128MB memory and 60 second timeout for mysql.  apache has a 60 second timeout too.  Any help?