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 useless cgroup v1 code,
2) some common structures like task_struct and mem_cgroup have never used
cgroup v1-specific members,
3) some code paths have additional checks which are not needed.
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/internal.h header
3) introducing the CONFIG_MEMCG_V1 config option, turned on by default
4) making memcontrol-v1.c to compile only if CONFIG_MEMCG_V1 is set
5) putting unused struct memory_cgroup and task_struct members under
CONFIG_MEMCG_V1 as well.
This is an RFC version, which is not 100% polished yet, so but it would be great
to discuss and agree on the overall approach.
Some open questions, opinions are appreciated:
1) I consider renaming non-static functions in memcontrol-v1.c to have
mem_cgroup_v1_ prefix. Is this a good idea?
2) Do we want to extend it beyond the memory controller? Should
3) Is it better to use a new include/linux/memcontrol-v1.h instead of
mm/internal.h? Or mm/memcontrol-v1.h.
diffstat:
include/linux/memcontrol.h | 165 ++++---
include/linux/sched.h | 5 +-
init/Kconfig | 7 +
mm/Makefile | 2 +
mm/internal.h | 124 +++++
mm/memcontrol-v1.c | 2941 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
mm/memcontrol.c | 4121 ++++++++++++++++++++++---------------------------------------------------------------------------------------------------------------------------------
7 files changed, 3765 insertions(+), 3600 deletions(-)
Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Roman Gushchin (9):
mm: memcg: introduce memcontrol-v1.c
mm: memcg: move soft limit reclaim code to memcontrol-v1.c
mm: memcg: move charge migration code to memcontrol-v1.c
mm: memcg: move legacy memcg event code into memcontrol-v1.c
mm: memcg: move cgroup v1 interface files to memcontrol-v1.c
mm: memcg: move cgroup v1 oom handling code into memcontrol-v1.c
mm: memcg: put cgroup v1-specific code under a config option
mm: memcg: put corresponding struct mem_cgroup members under
CONFIG_MEMCG_V1
mm: memcg: put cgroup v1-related members of task_struct under config
option
include/linux/memcontrol.h | 165 +-
include/linux/sched.h | 5 +-
init/Kconfig | 7 +
mm/Makefile | 2 +
mm/internal.h | 124 ++
mm/memcontrol-v1.c | 2941 +++++++++++++++++++++++++
mm/memcontrol.c | 4121 ++++++------------------------------
7 files changed, 3765 insertions(+), 3600 deletions(-)
create mode 100644 mm/memcontrol-v1.c
--
2.43.2
