Since Kame expressed the wish to see a context-based method to skip
accounting for caches, I came up with the following proposal for
your appreciation.
It basically works in the same way as preempt_disable()/preempt_enable():
By marking a region under which all allocations will be accounted
to the root memcg.
I basically see two main advantages of it:
* No need to clutter the code with *_noaccount functions; they could
become specially widespread if we needed to skip accounting for
kmalloc variants like track, zalloc, etc.
* Works with other caches, not only kmalloc; specially interesting
since during cache creation we touch things like cache_cache,
that could very well we wrapped inside a noaccount region.
However:
* It touches task_struct
* It is harder to keep drivers away from using it. With
kmalloc_no_account we could simply not export it. Here, one can
always set this in the task_struct...
Let me know what you think of it.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
---
include/linux/sched.h | 1 +
mm/memcontrol.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 81a173c..516a9fe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1613,6 +1613,7 @@ struct task_struct {
unsigned long nr_pages; /* uncharged usage */
unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
} memcg_batch;
+ int memcg_kmem_skip_account;
#endif
#ifdef CONFIG_HAVE_HW_BREAKPOINT
atomic_t ptrace_bp_refcnt;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8c7c404..833f4cd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -479,6 +479,33 @@ struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
EXPORT_SYMBOL(tcp_proto_cgroup);
#endif /* CONFIG_INET */
+static void memcg_stop_kmem_account(void)
+{
+ struct task_struct *p;
+
+ if (!current->mm)
+ return;
+
+ p = rcu_dereference(current->mm->owner);
+ if (p) {
+ task_lock(p);
+ p->memcg_kmem_skip_account = true;
+ }
+}
+
+static void memcg_start_kmem_account(void)
+{
+ struct task_struct *p;
+
+ if (!current->mm)
+ return;
+
+ p = rcu_dereference(current->mm->owner);
+ if (p) {
+ p->memcg_kmem_skip_account = false;
+ task_unlock(p);
+ }
+}
char *mem_cgroup_cache_name(struct mem_cgroup *memcg, struct kmem_cache *cachep)
{
char *name;
@@ -541,7 +568,9 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
if (new_cachep)
goto out;
+ memcg_stop_kmem_account();
new_cachep = kmem_cache_dup(memcg, cachep);
+ memcg_start_kmem_account();
if (new_cachep == NULL) {
new_cachep = cachep;
@@ -634,7 +663,9 @@ static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
if (!css_tryget(&memcg->css))
return;
+ memcg_stop_kmem_account();
cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
+ memcg_start_kmem_account();
if (cw == NULL) {
css_put(&memcg->css);
return;
@@ -678,6 +709,9 @@ struct kmem_cache *__mem_cgroup_get_kmem_cache(struct kmem_cache *cachep,
VM_BUG_ON(idx == -1);
p = rcu_dereference(current->mm->owner);
+ if (p->memcg_kmem_skip_account)
+ return cachep;
+
memcg = mem_cgroup_from_task(p);
if (!mem_cgroup_kmem_enabled(memcg))
--
1.7.7.6
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