Messages in this thread | | | Date | Fri, 24 Mar 2006 15:45:59 -0800 | From | "Siddha, Suresh B" <> | Subject | more smpnice patch issues |
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more issues with smpnice patch...
a) consider a 4-way system (simple SMP system with no HT and cores) scenario where a high priority task (nice -20) is running on P0 and two normal priority tasks running on P1. load balance with smp nice code will never be able to detect an imbalance and hence will never move one of the normal priority tasks on P1 to idle cpus P2 or P3.
b) smpnice seems to break this patch..
[PATCH] sched: allow the load to grow upto its cpu_power http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0c117f1b4d14380baeed9c883f765ee023da8761
example scenario for this case: consider a numa system with two nodes, each node containing four processors. if there are two processes in node-0 and with node-1 being completely idle, your patch will move one of those processes to node-1 whereas the previous behavior will retain those two processes in node-0.. (in this case, in your code max_load will be less than busiest_load_per_task)
smpnice patch has complicated the load balance code... Very difficult to comprehend the side effects of this patch in the presence of different priority tasks...
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