In an attempt to raise the hit ratio for the parser cache, I've
increased the amount of memory available to memcached. Because the
client algorithm distributes keys to each available server equally,
without regard for the amount of memory in each one, it's necessary to
have multiple instances running on each machine, each instance having a
fixed amount of memory. We're using 15 instances with 512 MB of memory
each, for a total of 7.5 GB. The arrangement is:
bart: 2
bayle: 2
yongle: 4
rabanus: 4
will: 3
I wanted to put some on suda but I had trouble with installation. Keys
are distributed using the hash mod the number of instances, so whenever
we change the number of instances, most keys get lost. In other words,
adding more servers incurs a performance hit since the cache needs to be
rebuilt.
-- Tim Starling