Siddha, Suresh B wrote:
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.
Fix already sent.
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)
I think that the patch I sent to address a) above will also fix this
problem as find_busiest_queue() will no longer find node-0 as the
busiest group unless both of the processes in node-0 are on the same
CPU. This is because it now only considers groups that have at least
one CPU with more than one running task as candidates for being the
busiest group.
Implicit in this is the assumption that it's OK to move one of the tasks
from node-0 to node-1 if they're both on the same CPU within node-0.
Could you confirm this is OK?
Thanks,
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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