diff mbox series

[v2] memcg, kmem: further deprecate kmem.limit_in_bytes

Message ID 20211019053058.2873615-1-shakeelb@google.com (mailing list archive)
State New
Headers show
Series [v2] memcg, kmem: further deprecate kmem.limit_in_bytes | expand

Commit Message

Shakeel Butt Oct. 19, 2021, 5:30 a.m. UTC
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 <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
Changes since v1:
- Replaced EINVAL with ENOTSUPP on setting kmem limits.
- V1 was posted last year at [0].

[0] https://lore.kernel.org/all/20201118175726.2453120-1-shakeelb@google.com/

 .../admin-guide/cgroup-v1/memory.rst          |  6 ++--
 mm/memcontrol.c                               | 35 +++----------------
 2 files changed, 6 insertions(+), 35 deletions(-)

Comments

Muchun Song Oct. 19, 2021, 5:51 a.m. UTC | #1
On Tue, Oct 19, 2021 at 1:31 PM Shakeel Butt <shakeelb@google.com> 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.
>
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Acked-by: Roman Gushchin <guro@fb.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Cc: Vasily Averin <vvs@virtuozzo.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
> Changes since v1:
> - Replaced EINVAL with ENOTSUPP on setting kmem limits.
> - V1 was posted last year at [0].
>
> [0] https://lore.kernel.org/all/20201118175726.2453120-1-shakeelb@google.com/
>
>  .../admin-guide/cgroup-v1/memory.rst          |  6 ++--
>  mm/memcontrol.c                               | 35 +++----------------
>  2 files changed, 6 insertions(+), 35 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
> index 41191b5fb69d..9be961521743 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

Since memory.kmem.limit_in_bytes can not be set, how about removing
those instructions as well?

diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst
b/Documentation/admin-guide/cgroup-v1/memory.rst
index 41191b5fb69d..f710f36770fa 100644
--- a/Documentation/admin-guide/cgroup-v1/memory.rst
+++ b/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -518,11 +518,6 @@ 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
-------------

With this changes,

Reviewed-by: Muchun Song <songmuchun@bytedance.com>

Thanks.

> 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 linux-mm@kvack.org 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
>
diff mbox series

Patch

diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
index 41191b5fb69d..9be961521743 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
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 linux-mm@kvack.org 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);