On Wed 18-11-20 09:57:26, Shakeel Butt 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@xxxxxxxxxx>
I am not against this. I am just not sure whether one year is enough for
those users who tend to have a more considervative kernel upgrade path.
I am not worried about SLES user base much as we didn't even enable
KMEM accounting when it was still guarded by a config option. Not sure
about others though.
Considering the code cleanup is not that large, I would rather wait some
more. But you can add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Maybe we can ask Andrew to put it into mmotm for few releases.
> ---
> .../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 52688ae34461..cb993d80194d 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 -EINVAL.
> 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 45465c03a8d7..78d17b3181ad 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3075,28 +3075,14 @@ static void memcg_free_cache_id(int id)
> int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
> unsigned int nr_pages)
> {
> - struct page_counter *counter;
> int ret;
>
> ret = try_charge(memcg, gfp, nr_pages);
> if (ret)
> return ret;
>
> - 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);
> - return 0;
> - }
> - cancel_charge(memcg, nr_pages);
> - return -ENOMEM;
> - }
> + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
> + page_counter_charge(&memcg->kmem, nr_pages);
> return 0;
> }
>
> @@ -3769,17 +3755,6 @@ static void memcg_free_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;
> @@ -3845,10 +3820,8 @@ 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@xxxxxxxxx if you "
> - "depend on this functionality.\n");
> - ret = memcg_update_kmem_max(memcg, nr_pages);
> + /* kmem.limit_in_bytes is deprecated. */
> + ret = -EINVAL;
> break;
> case _TCP:
> ret = memcg_update_tcp_max(memcg, nr_pages);
> --
> 2.29.2.299.gdc1121823c-goog
--
Michal Hocko
SUSE Labs
