http://www.oracle.com/technetwork/java/javase/gc-tuning-6-140523.html
On Wed, Oct 27, 2010 at 9:30 PM, JKnight JKnight <beukni...@gmail.com> wrote: > Could you tell me why Cassandra use memory more than needed? > > > On Thu, Oct 28, 2010 at 9:15 AM, Nicholas Knight <nkni...@runawaynet.com> > wrote: >> >> Presumably you're on a 32-bit architecture (or at least a 32-bit JVM). >> 32-bit processes won't be able to address more than "X" amount of memory, >> where X would usually be >= 2GB, and < 4GB. >> >> The reason you can't use a full 4GB is that part of the address space is >> necessarily reserved by the OS kernel. Exactly how much is reserved depends >> on the OS, version thereof, and/or configuration, but at least 0.5-1GB is >> usually a safe bet, so the behavior you see is exactly as expected. >> >> If your hardware is 64-bit, make sure you're running a 64-bit OS and a >> 64-bit JVM. If you're stuck on 32-bit hardware that just happens to have >> lots of RAM, you could run multiple Cassandra instances on each box.. >> >> -NK >> >> >> On Oct 28, 2010, at 10:04 AM, JKnight JKnight wrote: >> >> > Hi all, >> > >> > When I config Maximum heap size -Xmx4G, the memory will consume to 3.5G. >> > When I call Perform GC (jconsole), the used memory reduce to 1G. >> > >> > When I config Maximum heap size -Xmx2G, Cassandra system run well. >> > >> > Is that Casandra problem? >> > I want Cassandra use memory more effective. How can I do that? >> > >> > Thank a lot for support. >> > -- >> > Best regards, >> > JKnight >> > > > > -- > Best regards, > JKnight > -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of Riptano, the source for professional Cassandra support http://riptano.com
