Hans, You can change memory requirements for tasks of a single job, but not of a single task inside that job.
This is briefly how the 0.20 framework (by default) works: TT has notions only of "slots", and carries a maximum _number_ of simultaneous slots it may run. It does not know of what each task, occupying one slot, would demand in resource-terms. Your job then supplies a # of map tasks, and amount of memory required per map task in general, as a configuration. TTs then merely start the task JVMs with the provided heap configuration. On Sun, Mar 11, 2012 at 11:24 AM, Hans Uhlig <huh...@uhlisys.com> wrote: > That was a typo in my email not in the configuration. Is the memory reserved > for the tasks when the task tracker starts? You seem to be suggesting that I > need to set the memory to be the same for all map tasks. Is there no way to > override for a single map task? > > > On Sat, Mar 10, 2012 at 8:41 PM, Harsh J <ha...@cloudera.com> wrote: >> >> Hans, >> >> Its possible you may have an typo issue: mapred.map.child.jvm.opts - >> Such a property does not exist. Perhaps you wanted >> "mapred.map.child.java.opts"? >> >> Additionally, the computation you need to do is (# of map slots on a >> TT * per-map-task-heap-requirement) should be at least < (Total RAM - >> 2/3 GB). With your 4 GB requirement, I guess you can support a max of >> 6-7 slots per machine (i.e. Not counting reducer heap requirements in >> parallel). >> >> On Sun, Mar 11, 2012 at 9:30 AM, Hans Uhlig <huh...@uhlisys.com> wrote: >> > I am attempting to speed up a mapping process whose input is GZIP >> > compressed >> > CSV files. The files range from 1-2GB, I am running on a Cluster where >> > each >> > node has a total of 32GB memory available to use. I have attempted to >> > tweak >> > mapred.map.child.jvm.opts with -Xmx4096mb and io.sort.mb to 2048 to >> > accommodate the size but I keep getting java heap errors or other memory >> > related problems. My row count per mapper is well below >> > Integer.MAX_INTEGER >> > limit by several orders of magnitude and the box is NOT using anywhere >> > close >> > to its full memory allotment. How can I specify that this map task can >> > have >> > 3-4 GB of memory for the collection, partition and sort process without >> > constantly spilling records to disk? >> >> >> >> -- >> Harsh J > > -- Harsh J
