Peter Williams wrote:
Siddha, Suresh B wrote:
On Sun, Apr 02, 2006 at 05:08:33PM +1000, Peter Williams wrote:
Siddha, Suresh B wrote:
Peter,
There are still issues which we need to address.. These are surfacing
as we are patching issue by issue(instead of addressing the root
issue, which
is: presence of high priority tasks messes up load balancing of normal
priority tasks..)
for example
a) on a simple 4-way MP system, if we have one high priority and 4
normal
priority tasks, with smpnice we would like to see the high priority
task
scheduled on one cpu, two other cpus getting one normal task each
and the
fourth cpu getting the remaining two normal tasks. but with smpnice
that extra normal priority task keeps jumping from one cpu to
another cpu having
the normal priority task.
This is because of the busiest_has_loaded_cpus, nr_loaded_cpus
logic.. We
are not including the cpu with high priority task in max_load
calculations
but including that in total and avg_load calcuations.. leading to
max_load <
avg_load and load balance between cpus running normal priority
tasks(2 Vs 1)
will always show imbalanace as one normal priority and the extra normal
priority task will keep moving from one cpu to another cpu having
normal priority task..
I can't see anything like this in the code.
Don't you see a condition where max_load < avg_load(as mentioned in the
above example) and in this case, code ignores avg_load and imbalance
will aways be the extra normal priority task( coming from
"max_load - busiest_load_per_task") and this normal priority task
keeps hopping from one cpu to another cpu having normal priority task..
Can you send a patch to fix what you think the problem in the is?
I am looking at ways in fixing all these issues cleanly... I don't have
a clean solution yet...
OK. I think this means some fiddling with avg_load may be necessary in
some cases but this will be complex. I'm not really happy about making
this code more complex until some of the current unnecessary complexity
is removed. I.e. until a proper solution to the problem of triggering
active_load_balance() is implemented.
I forgot to mention that I've been looking at whether mucking around
with avg_load is necessary and so far have been unable to convince
myself that it is. Your argument above hasn't changed that opinion.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
