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SubjectRe: [PATCH 3/4] memcg: get rid of percpu_charge_mutex lock
On Thu 21-07-11 13:47:04, Michal Hocko wrote:
> On Thu 21-07-11 19:30:51, KAMEZAWA Hiroyuki wrote:
> > On Thu, 21 Jul 2011 09:58:24 +0200
> > Michal Hocko <mhocko@suse.cz> wrote:
[...]
> > > --- a/mm/memcontrol.c
> > > +++ b/mm/memcontrol.c
> > > @@ -2166,7 +2165,8 @@ static void drain_all_stock(struct mem_cgroup *root_mem, bool sync)
> > >
> > > for_each_online_cpu(cpu) {
> > > struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
> > > - if (test_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
> > > + if (root_mem == stock->cached &&
> > > + test_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
> > > flush_work(&stock->work);
> >
> > Doesn't this new check handle hierarchy ?
> > css_is_ancestor() will be required if you do this check.
>
> Yes you are right. Will fix it. I will add a helper for the check.

Here is the patch with the helper. The above will then read
if (mem_cgroup_same_or_subtree(root_mem, stock->cached))

---
From b963a9f4dac61044daac49700f84b7819d7c2f53 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.cz>
Date: Thu, 21 Jul 2011 13:54:13 +0200
Subject: [PATCH] memcg: add mem_cgroup_same_or_subtree helper

We are checking whether a given two groups are same or at least in the
same subtree of a hierarchy at several places. Let's make a helper for
it to make code easier to read.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
---
mm/memcontrol.c | 29 ++++++++++++++++++-----------
1 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8180cd9..8dbb9d6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1046,6 +1046,21 @@ void mem_cgroup_move_lists(struct page *page,
mem_cgroup_add_lru_list(page, to);
}

+/*
+ * Checks whether given mem is same or in the root_mem's
+ * hierarchy subtree
+ */
+static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_mem,
+ struct mem_cgroup *mem)
+{
+ if (root_mem != mem) {
+ return (root_mem->use_hierarchy &&
+ css_is_ancestor(&mem->css, &root_mem->css));
+ }
+
+ return true;
+}
+
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
{
int ret;
@@ -1065,10 +1080,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
* enabled in "curr" and "curr" is a child of "mem" in *cgroup*
* hierarchy(even if use_hierarchy is disabled in "mem").
*/
- if (mem->use_hierarchy)
- ret = css_is_ancestor(&curr->css, &mem->css);
- else
- ret = (curr == mem);
+ ret = mem_cgroup_same_or_subtree(mem, curr);
css_put(&curr->css);
return ret;
}
@@ -2150,13 +2162,8 @@ static void drain_all_stock(struct mem_cgroup *root_mem, bool sync)
mem = stock->cached;
if (!mem || !stock->nr_pages)
continue;
- if (mem != root_mem) {
- if (!root_mem->use_hierarchy)
- continue;
- /* check whether "mem" is under tree of "root_mem" */
- if (!css_is_ancestor(&mem->css, &root_mem->css))
- continue;
- }
+ if (!mem_cgroup_same_or_subtree(root_mem, mem))
+ continue;
if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
schedule_work_on(cpu, &stock->work);
}
--
1.7.5.4

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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