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Date: Tue, 20 Dec 2022 10:27:45 -0800
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: linux-mm@...ck.org
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
Shakeel Butt <shakeelb@...gle.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Muchun Song <muchun.song@...ux.dev>,
Andrew Morton <akpm@...ux-foundation.org>,
Roman Gushchin <roman.gushchin@...ux.dev>
Subject: [PATCH RFC 2/2] mm: kmem: add direct objcg pointer to task_struct
To charge a freshly allocated kernel object to a memory cgroup, the
kernel needs to obtain an objcg pointer. Currently it does it
indirectly by obtaining the memcg pointer first and then calling to
__get_obj_cgroup_from_memcg().
Usually tasks spend their entire life belonging to the same object
cgroup. So it makes sense to save the objcg pointer on task_struct
directly, so it can be obtained faster. It requires some work on fork,
exit and cgroup migrate paths, but these paths are way colder.
The old indirect way is still used for remote memcg charging.
Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
---
include/linux/sched.h | 4 +++
mm/memcontrol.c | 84 +++++++++++++++++++++++++++++++++++++------
2 files changed, 77 insertions(+), 11 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 853d08f7562b..e17be609cbcb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1435,6 +1435,10 @@ struct task_struct {
struct mem_cgroup *active_memcg;
#endif
+#ifdef CONFIG_MEMCG_KMEM
+ struct obj_cgroup *objcg;
+#endif
+
#ifdef CONFIG_BLK_CGROUP
struct request_queue *throttle_queue;
#endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 82828c51d2ea..e0547b224f40 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3001,23 +3001,29 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
__always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
{
struct mem_cgroup *memcg;
- struct obj_cgroup *objcg;
+ struct obj_cgroup *objcg = NULL;
if (in_task()) {
memcg = current->active_memcg;
-
- /* Memcg to charge can't be determined. */
- if (likely(!memcg) && (!current->mm || (current->flags & PF_KTHREAD)))
- return NULL;
+ if (unlikely(memcg))
+ goto from_memcg;
+
+ if (current->objcg) {
+ rcu_read_lock();
+ do {
+ objcg = READ_ONCE(current->objcg);
+ } while (objcg && !obj_cgroup_tryget(objcg));
+ rcu_read_unlock();
+ }
} else {
memcg = this_cpu_read(int_active_memcg);
- if (likely(!memcg))
- return NULL;
+ if (unlikely(memcg))
+ goto from_memcg;
}
+ return objcg;
+from_memcg:
rcu_read_lock();
- if (!memcg)
- memcg = mem_cgroup_from_task(current);
objcg = __get_obj_cgroup_from_memcg(memcg);
rcu_read_unlock();
return objcg;
@@ -6303,6 +6309,28 @@ static void mem_cgroup_move_task(void)
mem_cgroup_clear_mc();
}
}
+
+#ifdef CONFIG_MEMCG_KMEM
+static void mem_cgroup_fork(struct task_struct *task)
+{
+ struct mem_cgroup *memcg;
+
+ rcu_read_lock();
+ memcg = mem_cgroup_from_task(task);
+ if (!memcg || mem_cgroup_is_root(memcg))
+ task->objcg = NULL;
+ else
+ task->objcg = __get_obj_cgroup_from_memcg(memcg);
+ rcu_read_unlock();
+}
+
+static void mem_cgroup_exit(struct task_struct *task)
+{
+ if (task->objcg)
+ obj_cgroup_put(task->objcg);
+}
+#endif
+
#else /* !CONFIG_MMU */
static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
{
@@ -6317,7 +6345,7 @@ static void mem_cgroup_move_task(void)
#endif
#ifdef CONFIG_LRU_GEN
-static void mem_cgroup_attach(struct cgroup_taskset *tset)
+static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset)
{
struct task_struct *task;
struct cgroup_subsys_state *css;
@@ -6335,10 +6363,38 @@ static void mem_cgroup_attach(struct cgroup_taskset *tset)
task_unlock(task);
}
#else
+static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset) {}
+#endif /* CONFIG_LRU_GEN */
+
+#ifdef CONFIG_MEMCG_KMEM
+static void mem_cgroup_kmem_attach(struct cgroup_taskset *tset)
+{
+ struct task_struct *task;
+ struct cgroup_subsys_state *css;
+
+ cgroup_taskset_for_each(task, css, tset) {
+ struct mem_cgroup *memcg;
+
+ if (task->objcg)
+ obj_cgroup_put(task->objcg);
+
+ rcu_read_lock();
+ memcg = container_of(css, struct mem_cgroup, css);
+ task->objcg = __get_obj_cgroup_from_memcg(memcg);
+ rcu_read_unlock();
+ }
+}
+#else
+static void mem_cgroup_kmem_attach(struct cgroup_taskset *tset) {}
+#endif /* CONFIG_MEMCG_KMEM */
+
+#if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MEMCG_KMEM)
static void mem_cgroup_attach(struct cgroup_taskset *tset)
{
+ mem_cgroup_lru_gen_attach(tset);
+ mem_cgroup_kmem_attach(tset);
}
-#endif /* CONFIG_LRU_GEN */
+#endif
static int seq_puts_memcg_tunable(struct seq_file *m, unsigned long value)
{
@@ -6816,9 +6872,15 @@ struct cgroup_subsys memory_cgrp_subsys = {
.css_reset = mem_cgroup_css_reset,
.css_rstat_flush = mem_cgroup_css_rstat_flush,
.can_attach = mem_cgroup_can_attach,
+#if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MEMCG_KMEM)
.attach = mem_cgroup_attach,
+#endif
.cancel_attach = mem_cgroup_cancel_attach,
.post_attach = mem_cgroup_move_task,
+#ifdef CONFIG_MEMCG_KMEM
+ .fork = mem_cgroup_fork,
+ .exit = mem_cgroup_exit,
+#endif
.dfl_cftypes = memory_files,
.legacy_cftypes = mem_cgroup_legacy_files,
.early_init = 0,
--
2.39.0
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