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M.Baris Demiray wrote:
> > 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?
>
Close.
Probably it would be better to take the intersection of
(group->cpumask, p->cpus_allowed), and skip the group if
the intersection is empty.
In addition to that, do a patch for find_idlest_cpu that
skips cpus that aren't allowed. You needn't do the cpumask
check each time round the loop, again just take the
intersection of the group->cpumask and p->cpus_allowed, and
loop over that.
Wanna do a patch for that?
> 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.>
I don't think it does anything ;)
> Regards.> > Signed-off-by: M.Baris Demiray <baris@labristeknoloji.com>
>
> --- 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;
>
>
--
SUSE Labs, Novell Inc.
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