The deprecation process of kmem.limit_in_bytes started with the commit
0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also
explains in detail the motivation behind the deprecation. To summarize,
it is the unexpected behavior on hitting the kmem limit. This patch
moves the deprecation process to the next stage by disallowing to set
the kmem limit. In future we might just remove the kmem.limit_in_bytes
file completely.
Signed-off-by: Shakeel Butt <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Andrew Morton <[email protected]>
---
Changes since v2:
- Updated the documentation
Changes since v1:
- Replaced EINVAL with ENOTSUPP on setting kmem limits.
- V1 was posted last year at [0].
[0] https://lore.kernel.org/all/[email protected]/
.../admin-guide/cgroup-v1/memory.rst | 11 ++----
mm/memcontrol.c | 35 +++----------------
2 files changed, 6 insertions(+), 40 deletions(-)
diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
index 41191b5fb69d..faac50149a22 100644
--- a/Documentation/admin-guide/cgroup-v1/memory.rst
+++ b/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -87,10 +87,8 @@ Brief summary of control files.
memory.oom_control set/show oom controls.
memory.numa_stat show the number of memory usage per numa
node
- memory.kmem.limit_in_bytes set/show hard limit for kernel memory
- This knob is deprecated and shouldn't be
- used. It is planned that this be removed in
- the foreseeable future.
+ memory.kmem.limit_in_bytes This knob is deprecated and writing to
+ it will return -ENOTSUPP.
memory.kmem.usage_in_bytes show current kernel memory allocation
memory.kmem.failcnt show the number of kernel memory usage
hits limits
@@ -518,11 +516,6 @@ will be charged as a new owner of it.
charged file caches. Some out-of-use page caches may keep charged until
memory pressure happens. If you want to avoid that, force_empty will be useful.
- Also, note that when memory.kmem.limit_in_bytes is set the charges due to
- kernel pages will still be seen. This is not considered a failure and the
- write will still return success. In this case, it is expected that
- memory.kmem.usage_in_bytes == memory.usage_in_bytes.
-
5.2 stat file
-------------
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8f1d9c028897..49a76049a885 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2999,7 +2999,6 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
unsigned int nr_pages)
{
- struct page_counter *counter;
struct mem_cgroup *memcg;
int ret;
@@ -3009,21 +3008,8 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
if (ret)
goto out;
- if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
- !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) {
-
- /*
- * Enforce __GFP_NOFAIL allocation because callers are not
- * prepared to see failures and likely do not have any failure
- * handling code.
- */
- if (gfp & __GFP_NOFAIL) {
- page_counter_charge(&memcg->kmem, nr_pages);
- goto out;
- }
- cancel_charge(memcg, nr_pages);
- ret = -ENOMEM;
- }
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ page_counter_charge(&memcg->kmem, nr_pages);
out:
css_put(&memcg->css);
@@ -3715,17 +3701,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
}
#endif /* CONFIG_MEMCG_KMEM */
-static int memcg_update_kmem_max(struct mem_cgroup *memcg,
- unsigned long max)
-{
- int ret;
-
- mutex_lock(&memcg_max_mutex);
- ret = page_counter_set_max(&memcg->kmem, max);
- mutex_unlock(&memcg_max_mutex);
- return ret;
-}
-
static int memcg_update_tcp_max(struct mem_cgroup *memcg, unsigned long max)
{
int ret;
@@ -3791,10 +3766,8 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
ret = mem_cgroup_resize_max(memcg, nr_pages, true);
break;
case _KMEM:
- pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
- "Please report your usecase to [email protected] if you "
- "depend on this functionality.\n");
- ret = memcg_update_kmem_max(memcg, nr_pages);
+ /* kmem.limit_in_bytes is deprecated. */
+ ret = -ENOTSUPP;
break;
case _TCP:
ret = memcg_update_tcp_max(memcg, nr_pages);
--
2.33.0.1079.g6e70778dc9-goog
On Tue, 19 Oct 2021 08:34:08 -0700 Shakeel Butt <[email protected]> wrote:
> The deprecation process of kmem.limit_in_bytes started with the commit
> 0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also
> explains in detail the motivation behind the deprecation. To summarize,
> it is the unexpected behavior on hitting the kmem limit. This patch
> moves the deprecation process to the next stage by disallowing to set
> the kmem limit. In future we might just remove the kmem.limit_in_bytes
> file completely.
>
> ...
>
> @@ -3791,10 +3766,8 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
> ret = mem_cgroup_resize_max(memcg, nr_pages, true);
> break;
> case _KMEM:
> - pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
> - "Please report your usecase to [email protected] if you "
> - "depend on this functionality.\n");
> - ret = memcg_update_kmem_max(memcg, nr_pages);
> + /* kmem.limit_in_bytes is deprecated. */
> + ret = -ENOTSUPP;
> break;
> case _TCP:
> ret = memcg_update_tcp_max(memcg, nr_pages);
checkpatch said "ENOTSUPP is not a SUSV4 error code, prefer EOPNOTSUPP"?
On Tue, Oct 19, 2021 at 12:51 PM Andrew Morton
<[email protected]> wrote:
>
> On Tue, 19 Oct 2021 08:34:08 -0700 Shakeel Butt <[email protected]> wrote:
>
> > The deprecation process of kmem.limit_in_bytes started with the commit
> > 0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also
> > explains in detail the motivation behind the deprecation. To summarize,
> > it is the unexpected behavior on hitting the kmem limit. This patch
> > moves the deprecation process to the next stage by disallowing to set
> > the kmem limit. In future we might just remove the kmem.limit_in_bytes
> > file completely.
> >
> > ...
> >
> > @@ -3791,10 +3766,8 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
> > ret = mem_cgroup_resize_max(memcg, nr_pages, true);
> > break;
> > case _KMEM:
> > - pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
> > - "Please report your usecase to [email protected] if you "
> > - "depend on this functionality.\n");
> > - ret = memcg_update_kmem_max(memcg, nr_pages);
> > + /* kmem.limit_in_bytes is deprecated. */
> > + ret = -ENOTSUPP;
> > break;
> > case _TCP:
> > ret = memcg_update_tcp_max(memcg, nr_pages);
>
> checkpatch said "ENOTSUPP is not a SUSV4 error code, prefer EOPNOTSUPP"?
I should have run checkpatch and Andrew, please replace ENOTSUPP with
EOPNOTSUPP. Thanks for catching this.