First of all, "mapred.tasktracker.map.tasks.maximum" and "mapred.tasktracker.reduce.tasks.maximum" are both set to 2 in hadoop-default.xml file; this file is read before hadoop-site.xml file so any properties that aren't set in hadoop-site.xml will follow the values set in hadoop-default.xml. As for the question on why only one core is utilized... I think it really depends on the process scheduling of the underlying OS. It's not like two tasks (two JVM subprocesses spawned by the tasktracker) will always run on independent cores as there are other processes which need one or more cores to be run.
By the way, what tools did you use to find out which tasks (or processes) use which cores? /Taeho On Wed, Oct 8, 2008 at 1:01 PM, Alex Loddengaard <[EMAIL PROTECTED]>wrote: > Taeho, I was going to suggest this change as well, but it's documented that > "mapred.tasktracker.map.tasks.maximum" defaults to 2. Can you explain why > Elia is only having one core utilized when this config option is set to 2? > > Here is the documentation I'm referring to: > <http://hadoop.apache.org/core/docs/r0.18.1/cluster_setup.html> > > Alex > > On Tue, Oct 7, 2008 at 8:27 PM, Taeho Kang <[EMAIL PROTECTED]> wrote: > > > You can have your node (tasktracker) running more than 1 task > > simultaneously. > > You may set "mapred.tasktracker.map.tasks.maximum" and > > "mapred.tasktracker.reduce.tasks.maximum" properties found in > > hadoop-site.xml file. You should change hadoop-site.xml file on all your > > slave nodes depending on how many cores each slave has. For example, you > > don't really want to have 8 tasks running at once on a 2 core machine. > > > > /Taeho > > > > On Wed, Oct 8, 2008 at 5:53 AM, Elia Mazzawi > > <[EMAIL PROTECTED]>wrote: > > > > > hello, > > > > > > I have some dual core nodes, and I've noticed hadoop is only running 1 > > > instance, and so is only using 1 on the CPU's on each node. > > > is there a configuration to tell it to run more than once? > > > or do i need to turn each machine into 2 nodes? > > > > > > Thanks. > > > > > >
