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SubjectRe: [PATCH 0/4] cpuset: cleanups and fixes
On Thu, 26 Feb 2009 15:02:15 +0800
Li Zefan <lizf@cn.fujitsu.com> wrote:

> This patchset mainly simplifies update_tasks_nodemask() and makes it
> return void (won't fail), thus fix a case that writing to cpuset.mems
> returns -ENOMEM but its mems_allowed has been changed.
>
> [PATCH 1/4] cgroups: add 'data' field to struct cgroup_scanner
> [PATCH 2/4] cpuset: rewrite update_tasks_nodemask()
> [PATCH 3/4] cpuset: avoid changing cpuset's mems when errno returned
> [PATCH 4/4] cpuset: remove struct cpuset_hotplug_scanner
>
Thank you. I think there is no problematic in your patch.

After reading your patch, I wonder we can improve this migration by
filter for cgroup_scan_tasks().

Assume a task with tons of threads in a cgroup and
- change nodemask
- migrate=1

Under current implemntation, cpuset_migrate_mm=>do_migrate_mm is called per
threads. This implies there will be big overhead, useless scanning of page
tables.

Can we add some checks as "Is this mm already migrated ?", anywhere ?
(we may need to add some another array, again...)

Thanks,
-Kame







> ---
> include/linux/cgroup.h | 1
> kernel/cpuset.c | 151 +++++++++++++++++++------------------------------
> 2 files changed, 62 insertions(+), 90 deletions(-)
> ---
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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