On Fri, Dec 7, 2012 at 9:27 AM, Michal Hocko [off-list ref] wrote:

On Fri 07-12-12 09:12:25, Ying Han wrote:

quoted

On Fri, Dec 7, 2012 at 12:58 AM, Michal Hocko [off-list ref] wrote:

quoted

On Thu 06-12-12 19:43:52, Ying Han wrote:
[...]

quoted

Forgot to mention, I was testing 3.7-rc6 with the two cgroup changes :

Could you give a try to -mm tree as well. There are some changes for
memcgs removal in that tree which are not in Linus's tree.

I will give a try, which patchset you have in mind so i can double check?

Have a look at ba5e0e6be1c76fd37508b2825372b28a90a5b729 in my tree.

Tried the tag: mmotm-2012-12-05-16-59 which includes the commit above.
The test runs better. Thank you for the pointer.

Looking into the patch itself, it includes 9 patchset where 6 from
cgroup and 3 from memcg.

    Michal Hocko (3):
          memcg: make mem_cgroup_reparent_charges non failing
          hugetlb: do not fail in hugetlb_cgroup_pre_destroy
          Merge remote-tracking branch
'tj-cgroups/cgroup-rmdir-updates' into mmotm

    Tejun Heo (6):
          cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs
          cgroup: kill CSS_REMOVED
          cgroup: use cgroup_lock_live_group(parent) in cgroup_create()
          cgroup: deactivate CSS's and mark cgroup dead before
invoking ->pre_destroy()
          cgroup: remove CGRP_WAIT_ON_RMDIR, cgroup_exclude_rmdir()
and cgroup_release_and_wakeup_rmdir()
          cgroup: make ->pre_destroy() return void

Any suggestion of the minimal patchset I need to apply for testing
this patchset? (hopefully not all of them)

--Ying

quoted

I didn't find the place where the css pins the memcg, which either
something i missed or not in place in my tree.

Yeah, it is carefully hidden ;).
css pins cgroup (last css_put will call dput on the cgroup dentry - via
css_dput_fn) and the last reference to memcg is dropped from ->destroy
callback (mem_cgroup_destroy) called from cgroup_diput.

quoted

I twisted the patch a bit to make it closer to your v2 version,
but instead keep the mem_cgroup_put() as well as using
css_tryget(). Again, my test is happy with it:

This is really strange, there must be something weird with ref counting
going on.
Anyway, thanks for your testing! I will try to enahance my testing some
more next week.

quoted

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f2eeee6..acec05a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -1004,6 +1004,7 @@ struct mem_cgroup *mem_cgroup_iter(struct

mem_cgroup *root,
                        if (prev && reclaim->generation != iter->generation) {
                                if (last_visited) {
                                        css_put(&last_visited->css);
+                                       mem_cgroup_put(last_visited);
                                        iter->last_visited = NULL;
                                }
                                spin_unlock(&iter->iter_lock);

@@ -1041,15 +1042,22 @@ struct mem_cgroup *mem_cgroup_iter(struct

mem_cgroup *root,
                if (reclaim) {
                        struct mem_cgroup *curr = memcg;

-                       if (last_visited)
+                       if (last_visited) {
                                css_put(&last_visited->css);
+                               mem_cgroup_put(last_visited);
+                       }

                        if (css && !memcg)
                                curr = container_of(css, struct
mem_cgroup, css);

                        /* make sure that the cached memcg is not removed */
-                       if (curr)
-                               css_get(&curr->css);
+                       if (curr) {
+                               mem_cgroup_get(curr);
+                               if (!css_tryget(&curr->css)) {
+                                       mem_cgroup_put(curr);
+                                       curr = NULL;
+                               }
+                       }
                        iter->last_visited = curr;

                        if (!css)


--Ying

quoted

--
Michal Hocko
SUSE Labs

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Michal Hocko
SUSE Labs

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