Commit 569c4f62 authored by Shakeel Butt's avatar Shakeel Butt Committed by Andrew Morton
Browse files

memcg: initiate deprecation of v1 soft limit 

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 provides more straightforward best effort (memory.low) and hard
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.

Link: https://lkml.kernel.org/r/20240814220021.3208384-3-shakeel.butt@linux.dev


Signed-off-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: default avatarT.J. Mercier <tjmercier@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d046ff46

Documentation/admin-guide/cgroup-v1/memory.rst

+6 −2
Original line number Diff line number Diff line
@@ -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

mm/memcontrol-v1.c

+3 −0
Original line number Diff line number Diff line
@@ -2545,6 +2545,9 @@ 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@kvack.org if you "

				     "depend on this functionality.\n");

			WRITE_ONCE(memcg->soft_limit, nr_pages);

			ret = 0;

		}