MySQL 6.0, Libevent

http://krow.livejournal.com/2008/01/01/

MySQL 6.0, Libevent
Jan. 1st, 2008 | 11:30 am

Currently in the 6.0 tree we have support for Libevent. This is one of those things I've been wanting to see
us do for years and it was finally completed a few weeks ago by Damien
Katz (aka CouchDB) with some help from Dmitri Lenev.

So what does this do? MySQL uses a 1:1 ratio for connections and
threads. Libevent allows us to pull threads into pools and use them
for connections. This is pretty awesome for 8way machines since
partially solves thread contention issues. Below is an example of
MyISAM doing large number of inserts with the number of users doing
inserts increasing (1-300 users). The graph shows the time taken for
each test run. Similar numbers show up when you run benchmarks with
Innodb (leave concurrent set to zero as you should normally do, this
will allow libevent to more effectively control the thread usage).
The green line shows the test running with 20 threads, while the blue
is unlimited. I do not have good rules of thumb yet for thread number
vs processors. The machine I used for this test is an 8way that I have
on loan from Intel. I will work out a similar test for Solaris once I
can get the code to compile there.