The APC object cache seems to be filling up any available shm_size.
Here's my current apc.php.
If I increase the
shm_size, it just takes more time to be filled.
The server is running just this one instance of WP MS.
I've verified the problem is with the object cache, not the opcode cache.
I'm also using Batcache. If I disable it, the cache still fills up, just a bit more slowly.
Fragmentation is consistently low, until the free memory is below 10%. At that point, fragmentation quickly ramps up to 100%. (As in a power-law graph.)
At this point, with a positive
user_ttl value, fragmentation remains at 100%.
If I set
user_ttl=0, it will mark one "cache full" count, and fragmentation goes back to 30%. Then back up. And so on.