I am running some experiments with the new O(1) scheduler. I am running my
experiments on a cluster of 10 machines, running Rocks4.0 Beta (which
comes with 2.6 kernel and hence the new scheduler)
The behaviour of scheduler is unexplained, and am getting some very
unexpected results. I read about the design of O(1) scheduler, and my
results completely DISAGREE with the theory. Any insight into explaining
this will be helpful.
--------------------------CASE 1-------------------------------------------
On a dual processor CPU, I have 2 processes running P1 and P2.
Here is snapshot of CPU utilization:
User Sys Nice
CPU1 40 30 0 P1
CPU2 40 30 0 P2
Now I add a niced process with nice value =19. So I expect it to utilize
the left over 30% CPU on either one of the CPUs. But instead the new
snapshot of the system is
User Sys Nice
CPU1 0 0 100 niced_process
CPU2 50 40 0 P1 & P2
So overall the nice process finishes in time. And normal process gets
slowed down by 30-40 %.
**NOTE: P1 and P2 and MPI jobs, so they wait on gettting data from other
nodes and consume only 70% CPU max.
nice process is cpu hog and consume 100% CPU
---------------------------------------------------------------------
--------------------------CASE 2-------------------------------------------
On a dual processor CPU, I have 2 processes running P1 and P2. But this
time P1 and P2 are CPU hogs themselves
Here is snapshot of CPU utilization:
User Sys Nice
CPU1 100 0 0 P1
CPU2 100 0 0 P2
Now I add a niced process with nice value =19.
User Sys Nice
CPU1 100 0 0 P1
CPU2 95 0 5 P2 & niced_process
This is GREAT! As expected.
But the CATCH is, if the niced_process is started first, and then P1 and
P2 are initiated, the behaviour is completely unexpected.
User Sys Nice
CPU1 0 0 100 niced_process
CPU2 0 0 0 -
Now I add P1 and P2
User Sys Nice
CPU1 0 0 100 niced_process
CPU2 100 0 0 P1 & P2
I expected the nice process to give up CPU to either P1 and P2.
NOTE: Here P1 , P2 and Niced_process are CPU hogs, and run at 100% cpu
utilization
---------------------------------------------------------------------
Any comments will be appreciated.
PLEASE EMAIL ME AT : [email protected]
Thanks
Deepti
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