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Subject[RFC][PATCH v7 06/14] memcg: add dirty limits to mem_cgroup
Date
Extend mem_cgroup to contain dirty page limits.

Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrea Righi <arighi@develer.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
Changelog since v5:
- To simplify this patch, deferred adding routines for kernel to query dirty
usage and limits to a later patch in this series.
- Collapsed __mem_cgroup_has_dirty_limit() into mem_cgroup_has_dirty_limit().
- Renamed __mem_cgroup_dirty_param() to mem_cgroup_dirty_param().
Changelog since v4:
- Added support for hierarchical dirty limits.
- Simplified __mem_cgroup_dirty_param().
- Simplified mem_cgroup_page_stat().
- Deleted mem_cgroup_nr_pages_item enum, which was added little value.
Instead the mem_cgroup_page_stat_item enum values are used to identify
memcg dirty statistics exported to kernel.
- Fixed overflow issues in mem_cgroup_hierarchical_free_pages().

Changelog since v3:
- Previously memcontrol.c used struct vm_dirty_param and vm_dirty_param() to
advertise dirty memory limits. Now struct dirty_info and
mem_cgroup_dirty_info() is used to share dirty limits between memcontrol and
the rest of the kernel.
- __mem_cgroup_has_dirty_limit() now returns false if use_hierarchy is set.
- memcg_hierarchical_free_pages() now uses parent_mem_cgroup() and is simpler.
- created internal routine, __mem_cgroup_has_dirty_limit(), to consolidate the
logic.

Changelog since v1:
- Rename (for clarity):
- mem_cgroup_write_page_stat_item -> mem_cgroup_page_stat_item
- mem_cgroup_read_page_stat_item -> mem_cgroup_nr_pages_item
- Removed unnecessary get_ prefix from get_xxx() functions.
- Avoid lockdep warnings by using rcu_read_[un]lock() in
mem_cgroup_has_dirty_limit().

mm/memcontrol.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 50 insertions(+), 1 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a4cb991..f496677 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -216,6 +216,14 @@ struct mem_cgroup_eventfd_list {
static void mem_cgroup_threshold(struct mem_cgroup *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);

+/* Dirty memory parameters */
+struct vm_dirty_param {
+ int dirty_ratio;
+ int dirty_background_ratio;
+ unsigned long dirty_bytes;
+ unsigned long dirty_background_bytes;
+};
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -260,6 +268,10 @@ struct mem_cgroup {
atomic_t refcnt;

unsigned int swappiness;
+
+ /* control memory cgroup dirty pages */
+ struct vm_dirty_param dirty_param;
+
/* OOM-Killer disable */
int oom_kill_disable;

@@ -1309,6 +1321,36 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
return memcg->swappiness;
}

+/*
+ * Return true if the current memory cgroup has local dirty memory settings.
+ * There is an allowed race between the current task migrating in-to/out-of the
+ * root cgroup while this routine runs. So the return value may be incorrect if
+ * the current task is being simultaneously migrated.
+ */
+static bool mem_cgroup_has_dirty_limit(struct mem_cgroup *mem)
+{
+ return mem && !mem_cgroup_is_root(mem);
+}
+
+/*
+ * Returns a snapshot of the current dirty limits which is not synchronized with
+ * the routines that change the dirty limits. If this routine races with an
+ * update to the dirty bytes/ratio value, then the caller must handle the case
+ * where neither dirty_[background_]_ratio nor _bytes are set.
+ */
+static void mem_cgroup_dirty_param(struct vm_dirty_param *param,
+ struct mem_cgroup *mem)
+{
+ if (mem_cgroup_has_dirty_limit(mem)) {
+ *param = mem->dirty_param;
+ } else {
+ param->dirty_ratio = vm_dirty_ratio;
+ param->dirty_bytes = vm_dirty_bytes;
+ param->dirty_background_ratio = dirty_background_ratio;
+ param->dirty_background_bytes = dirty_background_bytes;
+ }
+}
+
static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
int cpu;
@@ -4917,8 +4959,15 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
mem->last_scanned_node = MAX_NUMNODES;
INIT_LIST_HEAD(&mem->oom_notify);

- if (parent)
+ if (parent) {
mem->swappiness = get_swappiness(parent);
+ mem_cgroup_dirty_param(&mem->dirty_param, parent);
+ } else {
+ /*
+ * The root cgroup dirty_param field is not used, instead,
+ * system-wide dirty limits are used.
+ */
+ }
atomic_set(&mem->refcnt, 1);
mem->move_charge_at_immigrate = 0;
mutex_init(&mem->thresholds_lock);
--
1.7.3.1


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