[PATCH 3/8] mm: memcontrol: give the kmem states more descriptive names

Johannes Weiner
2015-12-08T18:34:56Z

On any given memcg, the kmem accounting feature has three separate
states: not initialized, structures allocated, and actively accounting
slab memory. These are represented through a combination of the
kmem_acct_activated and kmem_acct_active flags, which is confusing.

Convert to a kmem_state enum with the states NONE, ALLOCATED, and
ONLINE. Then rename the functions to modify the state accordingly.
This follows the nomenclature of css object states more closely.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 15 ++++++++-----
mm/memcontrol.c | 52 ++++++++++++++++++++++------------------------
mm/slab_common.c | 4 ++--
mm/vmscan.c | 2 +-
4 files changed, 38 insertions(+), 35 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 189f04d..54dab4d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -152,6 +152,12 @@ struct mem_cgroup_thresholds {
struct mem_cgroup_threshold_ary *spare;
};

+enum memcg_kmem_state {
+ KMEM_NONE,
+ KMEM_ALLOCATED,
+ KMEM_ONLINE,
+};
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -233,8 +239,7 @@ struct mem_cgroup {
#if defined(CONFIG_MEMCG_KMEM)
/* Index in the kmem_cache->memcg_params.memcg_caches array */
int kmemcg_id;
- bool kmem_acct_activated;
- bool kmem_acct_active;
+ enum memcg_kmem_state kmem_state;
#endif

int last_scanned_node;
@@ -750,9 +755,9 @@ static inline bool memcg_kmem_enabled(void)
return static_branch_unlikely(&memcg_kmem_enabled_key);
}

-static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
+static inline bool memcg_kmem_online(struct mem_cgroup *memcg)
{
- return memcg->kmem_acct_active;
+ return memcg->kmem_state == KMEM_ONLINE;
}

/*
@@ -850,7 +855,7 @@ static inline bool memcg_kmem_enabled(void)
return false;
}

-static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
+static inline bool memcg_kmem_online(struct mem_cgroup *memcg)
{
return false;
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 02167db..22b8c4f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2357,7 +2357,7 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
struct page_counter *counter;
int ret;

- if (!memcg_kmem_is_active(memcg))
+ if (!memcg_kmem_online(memcg))
return 0;

if (!page_counter_try_charge(&memcg->kmem, nr_pages, &counter))
@@ -2840,14 +2840,13 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
}

#ifdef CONFIG_MEMCG_KMEM
-static int memcg_activate_kmem(struct mem_cgroup *memcg)
+static int memcg_online_kmem(struct mem_cgroup *memcg)
{
int err = 0;
int memcg_id;

BUG_ON(memcg->kmemcg_id >= 0);
- BUG_ON(memcg->kmem_acct_activated);
- BUG_ON(memcg->kmem_acct_active);
+ BUG_ON(memcg->kmem_state);

/*
* For simplicity, we won't allow this to be disabled. It also can't
@@ -2877,14 +2876,13 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg)

static_branch_inc(&memcg_kmem_enabled_key);
/*
- * A memory cgroup is considered kmem-active as soon as it gets
+ * A memory cgroup is considered kmem-online as soon as it gets
* kmemcg_id. Setting the id after enabling static branching will
* guarantee no one starts accounting before all call sites are
* patched.
*/
memcg->kmemcg_id = memcg_id;
- memcg->kmem_acct_activated = true;
- memcg->kmem_acct_active = true;
+ memcg->kmem_state = KMEM_ONLINE;
out:
return err;
}
@@ -2896,8 +2894,8 @@ static int memcg_update_kmem_limit(struct mem_cgroup *memcg,

mutex_lock(&memcg_limit_mutex);
/* Top-level cgroup doesn't propagate from root */
- if (!memcg_kmem_is_active(memcg)) {
- ret = memcg_activate_kmem(memcg);
+ if (!memcg_kmem_online(memcg)) {
+ ret = memcg_online_kmem(memcg);
if (ret)
goto out;
}
@@ -2917,11 +2915,12 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)

mutex_lock(&memcg_limit_mutex);
/*
- * If the parent cgroup is not kmem-active now, it cannot be activated
- * after this point, because it has at least one child already.
+ * If the parent cgroup is not kmem-online now, it cannot be
+ * onlined after this point, because it has at least one child
+ * already.
*/
- if (memcg_kmem_is_active(parent))
- ret = memcg_activate_kmem(memcg);
+ if (memcg_kmem_online(parent))
+ ret = memcg_online_kmem(memcg);
mutex_unlock(&memcg_limit_mutex);
return ret;
}
@@ -3568,22 +3567,21 @@ static int memcg_init_kmem(struct mem_cgroup *memcg)
return tcp_init_cgroup(memcg);
}

-static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
+static void memcg_offline_kmem(struct mem_cgroup *memcg)
{
struct cgroup_subsys_state *css;
struct mem_cgroup *parent, *child;
int kmemcg_id;

- if (!memcg->kmem_acct_active)
+ if (memcg->kmem_state != KMEM_ONLINE)
return;
-
/*
- * Clear the 'active' flag before clearing memcg_caches arrays entries.
- * Since we take the slab_mutex in memcg_deactivate_kmem_caches(), it
- * guarantees no cache will be created for this cgroup after we are
- * done (see memcg_create_kmem_cache()).
+ * Clear the online state before clearing memcg_caches array
+ * entries. The slab_mutex in memcg_deactivate_kmem_caches()
+ * guarantees that no cache will be created for this cgroup
+ * after we are done (see memcg_create_kmem_cache()).
*/
- memcg->kmem_acct_active = false;
+ memcg->kmem_state = KMEM_ALLOCATED;

memcg_deactivate_kmem_caches(memcg);

@@ -3614,9 +3612,9 @@ static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
memcg_free_cache_id(kmemcg_id);
}

-static void memcg_destroy_kmem(struct mem_cgroup *memcg)
+static void memcg_free_kmem(struct mem_cgroup *memcg)
{
- if (memcg->kmem_acct_activated) {
+ if (memcg->kmem_state == KMEM_ALLOCATED) {
memcg_destroy_kmem_caches(memcg);
static_branch_dec(&memcg_kmem_enabled_key);
WARN_ON(page_counter_read(&memcg->kmem));
@@ -3629,11 +3627,11 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
return 0;
}

-static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
+static void memcg_offline_kmem(struct mem_cgroup *memcg)
{
}

-static void memcg_destroy_kmem(struct mem_cgroup *memcg)
+static void memcg_free_kmem(struct mem_cgroup *memcg)
{
}
#endif
@@ -4286,7 +4284,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)

vmpressure_cleanup(&memcg->vmpressure);

- memcg_deactivate_kmem(memcg);
+ memcg_offline_kmem(memcg);

wb_memcg_offline(memcg);
}
@@ -4295,7 +4293,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);

- memcg_destroy_kmem(memcg);
+ memcg_free_kmem(memcg);
#ifdef CONFIG_INET
if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
static_branch_dec(&memcg_sockets_enabled_key);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index e016178..8c262e6 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -503,10 +503,10 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
mutex_lock(&slab_mutex);

/*
- * The memory cgroup could have been deactivated while the cache
+ * The memory cgroup could have been offlined while the cache
* creation work was pending.
*/
- if (!memcg_kmem_is_active(memcg))
+ if (!memcg_kmem_online(memcg))
goto out_unlock;

idx = memcg_cache_id(memcg);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 50e54c0..2dbc679 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -411,7 +411,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
struct shrinker *shrinker;
unsigned long freed = 0;

- if (memcg && !memcg_kmem_is_active(memcg))
+ if (memcg && !memcg_kmem_online(memcg))
return 0;

if (nr_scanned == 0)
--
2.6.3