Re: bbpress and memcache?
Because of mysql replication, using the mysql cache is probably impossible on wp.com
Once you move beyond a single mysql server, things get complicated fast.
But that’s specifically the environment memcache was written for, not single server systems.
(by the way, how large is the wp.com memcache pool? I bet it’s massive)
However I find the MySQL cache has not been turned on for many VPS/dedicated servers. That’s a performance showstopper and makes a huge difference when the same queries are being done over and over on a typical bbPress install. A PHP opcode cache is the next largest performance improvement.
Here is the typical breakdown for MySQL vs Memcached performance:
Cache Type Cache Gets/sec (higher is better)
Array Cache 365000 (this is local memory, fastest possible)
APC Cache 98000 (this is common memory via apc/eaccelertor/xcache)
File Cache 27000 (this is using the local disk cache)
Memcached Cache (TCP/IP) 12200 <<<<====---
MySQL Query Cache (TCP/IP) 9900
MySQL Query Cache (Unix Socket) 13500 <<<<===--- (local mysql server, with cache)
Selecting from table (TCP/IP) 5100 (remote mysql server, no cache)
Selecting from table (Unix Socket) 7400 (local mysql server, no cache)