On Fri, Oct 8, 2010 at 4:54 AM, Jedd Rashbrooke <jedd.rashbro...@imagini.net> wrote: > On 8 October 2010 02:05, Matthew Dennis <mden...@riptano.com> wrote: >> Also, in general, you probably want to set Xms = Xmx (regardless of the >> value you eventually decide on for that). > > Matthew - we'd just about reached that conclusion! Is it as big an > issue for clusters that are up for days at a time, with maybe Xmx:3G? > I'd kind of assumed that it'd get to its max pretty quickly. I haven't > been watching that with jconsole, but might watch it on the next startup.
The main reason to set Xms=Xmx is so mlockall can tag the entire heap as "don't swap this out" on startup. Secondarily whenever the heap resizes upwards the JVM does a stop-the-world gc, but no, not really a big deal when your uptime is in days or weeks. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of Riptano, the source for professional Cassandra support http://riptano.com
