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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 : dvyas@cs.uh.edu Thanks Deepti - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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