Hi, Chen I think it's due to the disk/network performance, I mean the speed of reading the content on disk/network into the local memory
if job3 hasn't complete data to start mappers, but job4 does, the scheduler would select the tasks of job4 from the list to run firstly, I think the so called FIFO principle is intended to setup stage, the firstly arrived job would be setup firstly Nan On Fri, Oct 15, 2010 at 1:29 AM, He Chen <airb...@gmail.com> wrote: > they arrived in 1 minute. I understand there will be a setup phase which > will use any free slot no matter map or reduce. > > My queue time is the period between the start of Map stage and the time job > is submitted. Because the setup phase has the higher priority than map and > reduce tasks. Any job submitted in the queue will setup no matter how many > previous map and reduce tasks need to be assigned. > > Now, I am sure the job3 setup stage finished earlier than job4's. However, > job3's map stage start later than job4's. BTW, they request same amount of > blocks. > > > On Thu, Oct 14, 2010 at 12:10 PM, abhishek sharma <absha...@usc.edu> > wrote: > > > What is the inter-arrival time between these jobs? > > > > There is a "set up" phase for jobs before they are launched. It is > > possible that the order of jobs can change due to slightly different > > set up times. Apart from the number of blocks, it may matter "where" > > these blocks lie. > > > > Abhishek > > > > On Thu, Oct 14, 2010 at 10:06 AM, He Chen <airb...@gmail.com> wrote: > > > Hi all > > > > > > I am testing the performance of my Hadoop clsuters with Hadoop Default > > FIFO > > > schedular. But I find a interesting phenomina. > > > > > > When I submit a series of jobs, some job will be executed earlier even > > they > > > are submitted late. All jobs are request same amount of blocks. For > > example: > > > job 1 submit at time 0 > > > job 2 submit at time 1 > > > job 3 submit at time 2 > > > job 4 submit at time 3 > > > > > > > > > job 4 's queue time is smaller than job3's queue time. This disobey the > > FIFO > > > principle. Any one can give a hint? > > > > > > Thanks > > > > > > Chen > > > > > >
