The commit is pushed to "branch-rh7-3.10.0-327.3.1-vz7.10.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.3.1.vz7.10.13
------>
commit 2f39f1ef3fa884221b04c9e5f9619f0bf4d504a8
Author: Vladimir Davydov <[email protected]>
Date: Fri Feb 26 16:19:34 2016 +0400
memcg: ignore memory.low for cgroups w/o tasks
It's OK to set memory.low for a cgroup to infinity. This might be useful
if no tasks are supposed to run inside the cgroup itself, but only in
its sub-cgroups (e.g. /machine.slice). In this case protection against
memory pressure originating on upper levels will be guarded solely by
memory.low configuration in sub-cgroups.
However, in the current implementation, in contrast to mainstream,
charges can appear in a cgroup even if there's no tasks in it - they can
be reparented from a dead sub-cgroup. If the cgroup has memory.low set
to inf, such reparented charges will not get reclaimed normally on
memory pressure, resulting in performance degradation in other cgroups.
To avoid that, let's ignore memory.low for cgroups w/o tasks.
https://jira.sw.ru/browse/PSBM-44192
Signed-off-by: Vladimir Davydov <[email protected]>
Reviewed-by: Kirill Tkhai <[email protected]>
---
mm/memcontrol.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ddd162a..6009ff5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1607,6 +1607,24 @@ bool mem_cgroup_low(struct mem_cgroup *root, struct
mem_cgroup *memcg)
if (res_counter_read_u64(&memcg->res, RES_USAGE) >= memcg->low)
return false;
+ /*
+ * XXX: It's OK to set memory.low for a cgroup to infinity. This might
+ * be useful if no tasks are supposed to run inside the cgroup itself,
+ * but only in its sub-cgroups (e.g. /machine.slice). In this case
+ * protection against memory pressure originating on upper levels will
+ * be guarded solely by memory.low configuration in sub-cgroups.
+ *
+ * However, in the current implementation, in contrast to mainstream,
+ * charges can appear in a cgroup even if there's no tasks in it - they
+ * can be reparented from a dead sub-cgroup. If the cgroup has
+ * memory.low set to inf, such reparented charges will not get
+ * reclaimed normally on memory pressure, resulting in performance
+ * degradation in other cgroups. To avoid that, let's ignore memory.low
+ * for cgroups w/o tasks.
+ */
+ if (cgroup_task_count(memcg->css.cgroup) == 0)
+ return false;
+
while (memcg != root) {
memcg = parent_mem_cgroup(memcg);
if (!memcg)
_______________________________________________
Devel mailing list
[email protected]
https://lists.openvz.org/mailman/listinfo/devel
