Kamezawa Hiroyuki [off-list ref] writes:

(2012/06/09 17:59), Aneesh Kumar K.V wrote:

quoted

From: "Aneesh Kumar K.V"<redacted>

This patchset add the charge and uncharge routines for hugetlb cgroup.
This will be used in later patches when we allocate/free HugeTLB
pages.

Signed-off-by: Aneesh Kumar K.V<redacted>

I'm sorry if following has been already pointed out.

quoted

---
  mm/hugetlb_cgroup.c |   87 +++++++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 87 insertions(+)

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 20a32c5..48efd5a 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c

@@ -105,6 +105,93 @@ static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
  	   return -EBUSY;
  }

+int hugetlb_cgroup_charge_page(int idx, unsigned long nr_pages,
+			       struct hugetlb_cgroup **ptr)
+{
+	int ret = 0;
+	struct res_counter *fail_res;
+	struct hugetlb_cgroup *h_cg = NULL;
+	unsigned long csize = nr_pages * PAGE_SIZE;
+
+	if (hugetlb_cgroup_disabled())
+		goto done;
+	/*
+	 * We don't charge any cgroup if the compound page have less
+	 * than 3 pages.
+	 */
+	if (hstates[idx].order<  2)
+		goto done;
+again:
+	rcu_read_lock();
+	h_cg = hugetlb_cgroup_from_task(current);
+	if (!h_cg)
+		h_cg = root_h_cgroup;
+
+	if (!css_tryget(&h_cg->css)) {
+		rcu_read_unlock();
+		goto again;
+	}
+	rcu_read_unlock();
+
+	ret = res_counter_charge(&h_cg->hugepage[idx], csize,&fail_res);
+	css_put(&h_cg->css);
+done:
+	*ptr = h_cg;
+	return ret;
+}
+

Memory cgroup uses very complicated 'charge' routine for handling pageout...
which gets sleep.

For hugetlbfs, it has not sleep routine, you can do charge in simple way.
I guess...get/put here is overkill.

For example, h_cg cannot be freed while it has tasks. So, if 'current' is
belongs to the cgroup, it cannot be disappear. Then, you don't need get/put,
additional atomic ops for holding cgroup.

	rcu_read_lock();
	h_cg = hugetlb_cgroup_from_task(current);
	ret = res_counter_charge(&h_cg->hugetpage[idx], csize,  &fail_res);
	rcu_read_unlock();

	return ret;

What if the task got moved ot of the cgroup and cgroup got deleted by an
rmdir ?

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>