[PATCH v3 07/11] memcg: add dirty limits to mem_cgroup

Greg Thelen
2010-10-19T00:44:14Z

Extend mem_cgroup to contain dirty page limits. Also add routines
allowing the kernel to query the dirty usage of a memcg.

These interfaces not used by the kernel yet. A subsequent commit
will add kernel calls to utilize these new routines.

Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrea Righi <arighi@develer.com>
---

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().

include/linux/memcontrol.h | 44 ++++++++++
mm/memcontrol.c | 186 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 229 insertions(+), 1 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ef2eec7..6f3a136 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -19,6 +19,7 @@

#ifndef _LINUX_MEMCONTROL_H
#define _LINUX_MEMCONTROL_H
+#include <linux/writeback.h>
#include <linux/cgroup.h>
struct mem_cgroup;
struct page_cgroup;
@@ -33,6 +34,30 @@ enum mem_cgroup_page_stat_item {
MEMCG_NR_FILE_UNSTABLE_NFS, /* # of NFS unstable pages */
};

+/* Cgroup memory statistics items exported to the kernel. */
+enum mem_cgroup_nr_pages_item {
+ MEMCG_NR_DIRTYABLE_PAGES,
+ MEMCG_NR_RECLAIM_PAGES,
+ MEMCG_NR_WRITEBACK,
+ MEMCG_NR_DIRTY_WRITEBACK_PAGES,
+};
+
+/* Dirty memory parameters */
+struct vm_dirty_param {
+ int dirty_ratio;
+ int dirty_background_ratio;
+ unsigned long dirty_bytes;
+ unsigned long dirty_background_bytes;
+};
+
+static inline void global_vm_dirty_param(struct vm_dirty_param *param)
+{
+ 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;
+}
+
extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
struct list_head *dst,
unsigned long *scanned, int order,
@@ -145,6 +170,10 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
mem_cgroup_update_page_stat(page, idx, -1);
}

+bool mem_cgroup_has_dirty_limit(void);
+void vm_dirty_param(struct vm_dirty_param *param);
+s64 mem_cgroup_page_stat(enum mem_cgroup_nr_pages_item item);
+
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask);
u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
@@ -326,6 +355,21 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
{
}

+static inline bool mem_cgroup_has_dirty_limit(void)
+{
+ return false;
+}
+
+static inline void vm_dirty_param(struct vm_dirty_param *param)
+{
+ global_vm_dirty_param(param);
+}
+
+static inline s64 mem_cgroup_page_stat(enum mem_cgroup_nr_pages_item item)
+{
+ return -ENOSYS;
+}
+
static inline
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3ac2693..f876919 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -233,6 +233,10 @@ 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;

@@ -1149,6 +1153,178 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
return swappiness;
}

+/*
+ * 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 both dirty_[background_]_ratio and _bytes are set.
+ */
+static void __mem_cgroup_dirty_param(struct vm_dirty_param *param,
+ struct mem_cgroup *mem)
+{
+ if (mem && !mem_cgroup_is_root(mem)) {
+ param->dirty_ratio = mem->dirty_param.dirty_ratio;
+ param->dirty_bytes = mem->dirty_param.dirty_bytes;
+ param->dirty_background_ratio =
+ mem->dirty_param.dirty_background_ratio;
+ param->dirty_background_bytes =
+ mem->dirty_param.dirty_background_bytes;
+ } else {
+ global_vm_dirty_param(param);
+ }
+}
+
+/*
+ * Get dirty memory parameters of the current memcg or global values (if memory
+ * cgroups are disabled or querying the root cgroup).
+ *
+ * The current task may be moved to other cgroup while we access cgroup changing
+ * the task's dirty limit. But a precise check is meaningless because the task
+ * can be moved after our access and writeback tends to take long time. At
+ * least, "memcg" will not be freed while holding rcu_read_lock().
+ */
+void vm_dirty_param(struct vm_dirty_param *param)
+{
+ struct mem_cgroup *memcg;
+
+ if (mem_cgroup_disabled()) {
+ global_vm_dirty_param(param);
+ return;
+ }
+
+ rcu_read_lock();
+ memcg = mem_cgroup_from_task(current);
+ __mem_cgroup_dirty_param(param, memcg);
+ rcu_read_unlock();
+}
+
+/*
+ * 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.
+ */
+bool mem_cgroup_has_dirty_limit(void)
+{
+ struct mem_cgroup *mem;
+ bool ret;
+
+ if (mem_cgroup_disabled())
+ return false;
+
+ rcu_read_lock();
+ mem = mem_cgroup_from_task(current);
+ ret = mem && !mem_cgroup_is_root(mem);
+ rcu_read_unlock();
+
+ return ret;
+}
+
+static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
+{
+ if (!do_swap_account)
+ return nr_swap_pages > 0;
+ return !memcg->memsw_is_minimum &&
+ (res_counter_read_u64(&memcg->memsw, RES_LIMIT) > 0);
+}
+
+static s64 mem_cgroup_local_page_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_nr_pages_item item)
+{
+ s64 ret;
+
+ switch (item) {
+ case MEMCG_NR_DIRTYABLE_PAGES:
+ ret = mem_cgroup_read_stat(mem, LRU_ACTIVE_FILE) +
+ mem_cgroup_read_stat(mem, LRU_INACTIVE_FILE);
+ if (mem_cgroup_can_swap(mem))
+ ret += mem_cgroup_read_stat(mem, LRU_ACTIVE_ANON) +
+ mem_cgroup_read_stat(mem, LRU_INACTIVE_ANON);
+ break;
+ case MEMCG_NR_RECLAIM_PAGES:
+ ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_DIRTY) +
+ mem_cgroup_read_stat(mem,
+ MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
+ break;
+ case MEMCG_NR_WRITEBACK:
+ ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_WRITEBACK);
+ break;
+ case MEMCG_NR_DIRTY_WRITEBACK_PAGES:
+ ret = mem_cgroup_read_stat(mem,
+ MEM_CGROUP_STAT_FILE_WRITEBACK) +
+ mem_cgroup_read_stat(mem,
+ MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
+ break;
+ default:
+ BUG();
+ break;
+ }
+ return ret;
+}
+
+static unsigned long long
+memcg_hierarchical_free_pages(struct mem_cgroup *mem)
+{
+ struct cgroup *cgroup;
+ unsigned long long min_free, free;
+
+ min_free = res_counter_read_u64(&mem->res, RES_LIMIT) -
+ res_counter_read_u64(&mem->res, RES_USAGE);
+ cgroup = mem->css.cgroup;
+ if (!mem->use_hierarchy)
+ goto out;
+
+ while (cgroup->parent) {
+ cgroup = cgroup->parent;
+ mem = mem_cgroup_from_cont(cgroup);
+ if (!mem->use_hierarchy)
+ break;
+ free = res_counter_read_u64(&mem->res, RES_LIMIT) -
+ res_counter_read_u64(&mem->res, RES_USAGE);
+ min_free = min(min_free, free);
+ }
+out:
+ /* Translate free memory in pages */
+ return min_free >> PAGE_SHIFT;
+}
+
+/*
+ * mem_cgroup_page_stat() - get memory cgroup file cache statistics
+ * @item: memory statistic item exported to the kernel
+ *
+ * Return the accounted statistic value.
+ */
+s64 mem_cgroup_page_stat(enum mem_cgroup_nr_pages_item item)
+{
+ struct mem_cgroup *mem;
+ struct mem_cgroup *iter;
+ s64 value;
+
+ rcu_read_lock();
+ mem = mem_cgroup_from_task(current);
+ if (mem && !mem_cgroup_is_root(mem)) {
+ /*
+ * If we're looking for dirtyable pages we need to evaluate
+ * free pages depending on the limit and usage of the parents
+ * first of all.
+ */
+ if (item == MEMCG_NR_DIRTYABLE_PAGES)
+ value = memcg_hierarchical_free_pages(mem);
+ else
+ value = 0;
+ /*
+ * Recursively evaluate page statistics against all cgroup
+ * under hierarchy tree
+ */
+ for_each_mem_cgroup_tree(iter, mem)
+ value += mem_cgroup_local_page_stat(iter, item);
+ } else
+ value = -EINVAL;
+ rcu_read_unlock();
+
+ return value;
+}
+
static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
int cpu;
@@ -4457,8 +4633,16 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
spin_lock_init(&mem->reclaim_param_lock);
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);
--
1.7.1