Do you know the break down of times for a mapper task takes to initialize and to execute the map function?
On Wed, Mar 4, 2009 at 8:44 AM, Sean Laurent <[email protected]>wrote: > On Tue, Mar 3, 2009 at 10:14 PM, Amar Kamat <[email protected]> wrote: > > > Yeah. May be its not the problem with the JobTracker. Can you check (via > > job history) what is the best and the worst task runtimes? You can > analyze > > the jobs after they complete. > > Amar > > > Okay, I ran the same job 35 times last night. Each job was exactly > identical > - it parsed 1000 identical files that were already stored in HDFS via a map > task (no reduce). Like all of my previous tests, each successive run took > longer than the previous run. > > Looking at the job history, the first run was the fastest; it took a total > of 2mins 28sec (setup: 2 secs, map: 2min 22sec, cleanup: 0sec). The last > run > was the slowest; it took a total of 22mins 31sec (setup: 16sec, map: 22mins > 14sec, cleanup: 16sec). > > Memory usage on the JT/NN machine, as reported by sar, slowly increased > over > the 7 hour window. Memory usage on a randomly selected DN/TT also steadily > increased over the 7 hour window but far more rapidly. We also looked at > I/O > usage and CPU utilization on both the JT/NN machine and the same randomly > selected DN/TT - nothing out of the ordinary. I/O waits (both from the I/O > subsystem level perspective and from the CPU's perspective) were > consistently low over the 7 hour window and did not fluctuate significantly > on any of the machines. CPU utilization on the JT/NN was practically > non-existent and hovered between 40%-60% on the DN/TT. > > -Sean >
