[PATCH 2.6.12-rc5-mm2] [sched] add allowed CPUs check into find_idlest_group()

[M.Baris Demiray]

Hello,
following patch adds check for allowed CPUs into
sched.c:find_idlest_group() -as told in comment line that had
removed-. But, I have several questions about that comment.

Firstly, I've understood it as "Check whether process p is allowed to
run on each CPU of to-be-found idlest group"; is that right?

If so, isn't it more appropriate to do check in find_idlest_cpu()?
Because, we're only interested in CPUs that are in idlest group
but doing a check in find_idlest_group() also checks for CPUs
that are not in idlest group (since we're traversing all the groups
in given domain). Checking this after finding the idlest group
(in find_idlest_cpu() with ordinary call order as in
sched_balance_self()) will save us from extra overhead.

Although I've questions in my mind, I'm sending a patch following
that comment. Any explanation and comment on patch will be
appreciated.

Regards.

Signed-off-by: M.Baris Demiray <baris@xxxxxxxxxxxxxxxxxxx>

--- linux-2.6.12-rc5-mm2/kernel/sched.c.orig	2005-06-05 
12:31:04.000000000 +0000
+++ linux-2.6.12-rc5-mm2/kernel/sched.c	2005-06-05 16:49:49.000000000 +0000
@@ -1040,7 +1040,12 @@
 		int i;

 		local_group = cpu_isset(this_cpu, group->cpumask);
-		/* XXX: put a cpus allowed check */
+
+		/* Check whether all CPUs in the group is allowed to run on */
+		for_each_cpu_mask(i, group->cpumask) {
+			if (!cpu_isset(i, p->cpus_allowed))
+				continue;
+		}

 		/* Tally up the load of all CPUs in the group */
 		avg_load = 0;


--
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unplugged. And many of them are no inert, so hopelessly dependent
on the system, that they will fight to protect it."
                                                         Morpheus



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