Great post on how Facebook continues to scale large with the help of memcached.
Since we’ve made all these changes, we have been able to scale memcached to handle 200,000 UDP requests per second with an average latency of 173 microseconds. The total throughput achieved is 300,000 UDP requests/s, but the latency at that request rate is too high to be useful in our system. This is an amazing increase from 50,000 UDP requests/s using the stock version of Linux and memcached.
We’re hoping to get our changes integrated into the official memcached repository soon, but until that happens, we’ve decided to release all our changes to memcached on github.
Good analysis in this post at HighScalability.com also.