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memcg: initiate deprecation of v1 tcp accounting

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Patch series "memcg: initiate deprecation of v1 features", v2.

Start the deprecation process of the memcg v1 features which we discussed
during LSFMMBPF 2024 [1].  For now add the warnings to collect the
information on how the current users are using these features.  Next we
will work on providing better alternatives in v2 (if needed) and fully
deprecate these features.

Link: https://lwn.net/Articles/974575 [1]


This patch (of 4):

Memcg v1 provides opt-in TCP memory accounting feature.  However it is
mostly unused due to its performance impact on the network traffic.  In
v2, the TCP memory is accounted in the regular memory usage and is
transparent to the users but they can observe the TCP memory usage through
memcg stats.

Let's initiate the deprecation process of memcg v1's tcp accounting
functionality and add warnings to gather if there are any users and if
there are, collect how they are using it and plan to provide them better
alternative in v2.

Link: https://lkml.kernel.org/r/20240814220021.3208384-1-shakeel.butt@linux.dev
Link: https://lkml.kernel.org/r/20240814220021.3208384-2-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shakeel Butt 2024-08-14 15:00:18 -07:00 committed by Andrew Morton
parent 98455eef80
commit d046ff46ee
2 changed files with 11 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
Documentation/admin-guide/cgroup-v1/memory.rst
View File

@ -105,10 +105,18 @@ Brief summary of control files.
memory.kmem.max_usage_in_bytes show max kernel memory usage recorded
memory.kmem.tcp.limit_in_bytes set/show hard limit for tcp buf memory
This knob is deprecated and shouldn't be
used.
memory.kmem.tcp.usage_in_bytes show current tcp buf memory allocation
This knob is deprecated and shouldn't be
used.
memory.kmem.tcp.failcnt show the number of tcp buf memory usage
hits limits
This knob is deprecated and shouldn't be
used.
memory.kmem.tcp.max_usage_in_bytes show max tcp buf memory usage recorded
This knob is deprecated and shouldn't be
used.
==================================== ==========================================
1. History

3
mm/memcontrol-v1.c
View File

@ -2534,6 +2534,9 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
ret = 0;
break;
case _TCP:
pr_warn_once("kmem.tcp.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_tcp_max(memcg, nr_pages);
break;
}