Cgroups v2 have been around for a while and many users have fully adopted them, so they never use cgroups v1 features and functionality. Yet they have to "pay" for the cgroup v1 support anyway: 1) the kernel binary contains an unused cgroup v1 code, 2) some code paths have additional checks which are not needed, 3) some common structures like task_struct and mem_cgroup contain unused cgroup v1-specific members. Cgroup v1's memory controller has a number of features that are not supported by cgroup v2 and their implementation is pretty much self contained. Most notably, these features are: soft limit reclaim, oom handling in userspace, complicated event notification system, charge migration. Cgroup v1-specific code in memcontrol.c is close to 4k lines in size and it's intervened with generic and cgroup v2-specific code. It's a burden on developers and maintainers. This patchset aims to solve these problems by: 1) moving cgroup v1-specific memcg code to the new mm/memcontrol-v1.c file, 2) putting definitions shared by memcontrol.c and memcontrol-v1.c into the mm/memcontrol-v1.h header, 3) introducing the CONFIG_MEMCG_V1 config option, turned off by default, 4) making memcontrol-v1.c to compile only if CONFIG_MEMCG_V1 is set. If CONFIG_MEMCG_V1 is not set, cgroup v1 memory controller is still available for mounting, however no memory-specific control knobs are present. This patchset is based against mm-unstable tree (b610f75d19a34), however a version based on mm-stable can be found here: https://github.com/rgushchin/linux/tree/memcontrol_v1.1-stable . rfc: https://lwn.net/Articles/973082/ v1: - switched to CONFIG_MEMCG_V1 being off by default based on LSFMMBPF discussion [1] - switched to memcg1_ prefix (Johannes) - many minor fixes - dropped patches which put struct memcg members under CONFIG_MEMCG_V1 (will post as a separate patchset) [1]: https://lwn.net/Articles/974575/ MAINTAINERS | 2 + include/linux/memcontrol.h | 156 ++++--- init/Kconfig | 9 + mm/Makefile | 2 + mm/memcontrol-v1.c | 2933 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ mm/memcontrol-v1.h | 132 ++++++ mm/memcontrol.c | 4169 +++++++++++++++++++++++++++--------------------------------------------------------------------------------------------------------------------------------------------------- mm/vmscan.c | 10 +- 8 files changed, 3794 insertions(+), 3619 deletions(-) Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx> Roman Gushchin (14): mm: memcg: introduce memcontrol-v1.c mm: memcg: move soft limit reclaim code to memcontrol-v1.c mm: memcg: rename soft limit reclaim-related functions mm: memcg: move charge migration code to memcontrol-v1.c mm: memcg: rename charge move-related functions mm: memcg: move legacy memcg event code into memcontrol-v1.c mm: memcg: rename memcg_check_events() mm: memcg: move cgroup v1 oom handling code into memcontrol-v1.c mm: memcg: rename memcg_oom_recover() mm: memcg: move cgroup v1 interface files to memcontrol-v1.c mm: memcg: make memcg1_update_tree() static mm: memcg: group cgroup v1 memcg related declarations mm: memcg: put cgroup v1-related members of task_struct under config option MAINTAINERS: add mm/memcontrol-v1.c/h to the list of maintained files MAINTAINERS | 2 + include/linux/memcontrol.h | 156 +- init/Kconfig | 9 + mm/Makefile | 2 + mm/memcontrol-v1.c | 2933 +++++++++++++++++++++++++ mm/memcontrol-v1.h | 132 ++ mm/memcontrol.c | 4141 ++++++------------------------------ mm/vmscan.c | 10 +- 8 files changed, 3780 insertions(+), 3605 deletions(-) create mode 100644 mm/memcontrol-v1.c create mode 100644 mm/memcontrol-v1.h -- 2.45.1
