APC cache fragmentation problem

[costarico]

I'm running APC (php cache) on a medium website (13 000 visits a day) on a CentOS server 5 running php 5.3.3 with APC 3.1.4 with 4Gb of RAM. In the last weeks I'm experiencing many "\[code\]unable to allocate memory for pool\[/code\]" errors in logs, and often the site goes down.I think the problem is in APC. From the stats I see that the cache is full after an hour or two, and the fragmentation always jumps to 100%. This are my config settings of apc.ini:\[code\]apc.cache_by_default 1apc.canonicalize 0apc.coredump_unmap 0apc.enable_cli 0apc.enabled 1apc.file_md5 0apc.file_update_protection 2apc.filters apc.gc_ttl 3600apc.include_once_override 0apc.lazy_classes 00apc.lazy_functions 0apc.max_file_size 1Mapc.mmap_file_mask /dev/zeroapc.num_files_hint 0apc.preload_path apc.report_autofilter 0apc.rfc1867 0apc.rfc1867_freq 0apc.rfc1867_name APC_UPLOAD_PROGRESSapc.rfc1867_prefix upload_apc.rfc1867_ttl 3600apc.shm_segments 1apc.shm_size 512Mapc.slam_defense 1apc.stat 1apc.stat_ctime 0apc.ttl 7200apc.use_request_time 1apc.user_entries_hint 0apc.user_ttl 7200apc.write_lock 1\[/code\]From APC stats I can see that the number of cached files is very high (40 000), and this is due to the plethora of cache files of phpbb and mediawiki. Do I have to prevent APC caching this files using \[code\]apc.filters\[/code\]? Are there solutions to the problem?