[PATCH] mm: memcg/percpu: account extra objcg space to memory cgroups

From: Qi Zheng
Date: Thu Nov 25 2021 - 23:28:43 EST


Similar to slab memory allocator, for each accounted percpu object
there is an extra space which is used to store obj_cgroup membership.
Charge it too.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
mm/percpu-internal.h | 17 +++++++++++++++++
mm/percpu.c | 10 +++++-----
2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h
index 639662c20c82..030a176b5b8e 100644
--- a/mm/percpu-internal.h
+++ b/mm/percpu-internal.h
@@ -113,6 +113,23 @@ static inline int pcpu_chunk_map_bits(struct pcpu_chunk *chunk)
return pcpu_nr_pages_to_map_bits(chunk->nr_pages);
}

+#ifdef CONFIG_MEMCG_KMEM
+/**
+ * pcpu_obj_full_size - helper to calculate size of each accounted object
+ * @size: size of area to allocate in bytes
+ *
+ * For each accounted object there is an extra space which is used to store
+ * obj_cgroup membership. Charge it too.
+ */
+static inline size_t pcpu_obj_full_size(size_t size)
+{
+ size_t extra_size =
+ size / PCPU_MIN_ALLOC_SIZE * sizeof(struct obj_cgroup *);
+
+ return size * num_possible_cpus() + extra_size;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
#ifdef CONFIG_PERCPU_STATS

#include <linux/spinlock.h>
diff --git a/mm/percpu.c b/mm/percpu.c
index 293009cc03ef..f5c9a3faadee 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1635,7 +1635,7 @@ static bool pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
if (!objcg)
return true;

- if (obj_cgroup_charge(objcg, gfp, size * num_possible_cpus())) {
+ if (obj_cgroup_charge(objcg, gfp, pcpu_obj_full_size(size))) {
obj_cgroup_put(objcg);
return false;
}
@@ -1656,10 +1656,10 @@ static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,

rcu_read_lock();
mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
- size * num_possible_cpus());
+ pcpu_obj_full_size(size));
rcu_read_unlock();
} else {
- obj_cgroup_uncharge(objcg, size * num_possible_cpus());
+ obj_cgroup_uncharge(objcg, pcpu_obj_full_size(size));
obj_cgroup_put(objcg);
}
}
@@ -1676,11 +1676,11 @@ static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
return;
chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = NULL;

- obj_cgroup_uncharge(objcg, size * num_possible_cpus());
+ obj_cgroup_uncharge(objcg, pcpu_obj_full_size(size));

rcu_read_lock();
mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
- -(size * num_possible_cpus()));
+ -pcpu_obj_full_size(size));
rcu_read_unlock();

obj_cgroup_put(objcg);
--
2.11.0