From d046ff46ee3b920ac617564226d2a0494d9af772 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Wed, 14 Aug 2024 15:00:18 -0700 Subject: [PATCH] memcg: initiate deprecation of v1 tcp accounting 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 Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton --- Documentation/admin-guide/cgroup-v1/memory.rst | 8 ++++++++ mm/memcontrol-v1.c | 3 +++ 2 files changed, 11 insertions(+) diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst index 9cde26d33843..0114d758beab 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -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 diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index ff972a35ecc5..89944f83afb3 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -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; }