On Sun, Jun 09, 2013 at 05:17:03PM +0800, Li Zefan wrote:
> Before moving tasks out of empty cpusets, update_tasks_nodemask()
> is called, which calls do_migrate_pages(xx, from, to). Then those
> tasks are moved to an ancestor, and do_migrate_pages() is called
> again.
>
> The first time: from = node_to_be_offlined, to = empty.
> The second time: from = empty, to = ancestor's nodemask.
>
> so looks like no pages will be migrated.
>
> Fix this by:
>
> - Don't call update_tasks_nodemask() on empty cpusets.
> - Pass cs->old_mems_allowed to do_migrate_pages().
>
> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
> ---
> kernel/cpuset.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index d1d6782..3cd68b8 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -1563,9 +1563,16 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
> struct cpuset *mems_oldcs = effective_nodemask_cpuset(oldcs);
>
> mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
> - if (is_memory_migrate(cs))
> - cpuset_migrate_mm(mm, &mems_oldcs->mems_allowed,
> + if (is_memory_migrate(cs)) {
> + /*
> + * old_mems_allowed is the same with mems_allowed here,
> + * except if this task is being moved automatically due
> + * to hotplug, and in this case mems_allowed is empty
> + * and old_mems_allowed is the offlined node.
> + */
Wouldn't it be better if the above explain why rather than what?
> + cpuset_migrate_mm(mm, &mems_oldcs->old_mems_allowed,
> &cpuset_attach_nodemask_to);
> + }
> mmput(mm);
> }
>
> @@ -2155,7 +2162,7 @@ retry:
> * for empty cpuset to take on ancestor's cpumask.
> */
> if ((sane && cpumask_empty(cs->cpus_allowed)) ||
> - !cpumask_empty(&off_cpus))
> + (!cpumask_empty(&off_cpus) && !cpumask_empty(cs->cpus_allowed)))
> update_tasks_cpumask(cs, NULL);
No biggie but maybe we want briefly explain the conditions being tested?
Thanks.
--
tejun
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