I have 2 web servers to provide PHP websites.

One server is : Apache + PHP-FPM + APC

The other : Apache with MPM-itk + APC.

For both of these servers, APC has no cache system entries but only users cache entries as you can see on the screenshot. APC with only users cache entries

APC configuration is :

apc.cache_by_default  1
apc.canonicalize  1
apc.coredump_unmap  0
apc.enable_cli  0
apc.enabled 1
apc.file_md5  0
apc.file_update_protection  2
apc.filters 
apc.gc_ttl  3600
apc.include_once_override 0
apc.lazy_classes  0
apc.lazy_functions  0
apc.max_file_size 2
apc.mmap_file_mask  
apc.num_files_hint  1000
apc.preload_path  
apc.report_autofilter 0
apc.rfc1867 0
apc.rfc1867_freq  0
apc.rfc1867_name  APC_UPLOAD_PROGRESS
apc.rfc1867_prefix  upload_
apc.rfc1867_ttl 3600
apc.shm_segments  1
apc.shm_size  256
apc.stat  1
apc.stat_ctime  0
apc.ttl 7200
apc.use_request_time  1
apc.user_entries_hint 4096
apc.user_ttl  7200
apc.write_lock  1

Does anyone know why APC acts like this and how to make it work well ?

Thank you for your help!