On Wed, Aug 14, 2024 at 3:00 PM Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
>
> Memcg v1 provides soft limit functionality for the best effort memory
> sharing between multiple workloads on a system. It is usually triggered
> through kswapd and at the moment does not reclaim kernel memory.
>
> Memcg v2 provide more straightforward best effort (memory.low) and hard
"provides"
> protection (memory.min) functionalities. Let's initiate the deprecation
> of soft limit from v1 and gather if v2 needs something more to move the
> existing v1 users to v2 regarding soft limit.
>
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Reviewed-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
> ---
> Changes since v1:
> - N/A
>
> Documentation/admin-guide/cgroup-v1/memory.rst | 8 ++++++--
> mm/memcontrol-v1.c | 3 +++
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
> index 0114d758beab..6831c6c16e3f 100644
> --- a/Documentation/admin-guide/cgroup-v1/memory.rst
> +++ b/Documentation/admin-guide/cgroup-v1/memory.rst
> @@ -78,6 +78,8 @@ Brief summary of control files.
> memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded
> memory.soft_limit_in_bytes set/show soft limit of memory usage
> This knob is not available on CONFIG_PREEMPT_RT systems.
> + This knob is deprecated and shouldn't be
> + used.
> memory.stat show various statistics
> memory.use_hierarchy set/show hierarchical account enabled
> This knob is deprecated and shouldn't be
> @@ -701,8 +703,10 @@ For compatibility reasons writing 1 to memory.use_hierarchy will always pass::
>
> # echo 1 > memory.use_hierarchy
>
> -7. Soft limits
> -==============
> +7. Soft limits (DEPRECATED)
> +===========================
> +
> +THIS IS DEPRECATED!
>
> Soft limits allow for greater sharing of memory. The idea behind soft limits
> is to allow control groups to use as much of the memory as needed, provided
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index b8e2ee454eaa..e0bb54e42011 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -2458,6 +2458,9 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
> if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> ret = -EOPNOTSUPP;
> } else {
> + pr_warn_once("soft_limit_in_bytes is deprecated and will be removed. "
> + "Please report your usecase to linux-mm@xxxxxxxxx if you "
> + "depend on this functionality.\n");
> WRITE_ONCE(memcg->soft_limit, nr_pages);
> ret = 0;
> }
> --
> 2.43.5
>
