On Wed, May 08, 2024 at 08:41:29PM -0700, Roman Gushchin wrote: > 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. Great patchset. The moves look clean and straight-forward to me on first glance. > This patchset aims to solve these problems by: > 1) moving cgroup v1-specific memcg code to the new mm/memcontrol-v1.c file, +1 > 2) putting definitions shared by memcontrol.c and memcontrol-v1.c into the > mm/internal.h header You proposed mm/memcontrol-v1.h below, IMO that's the best option. > 3) introducing the CONFIG_MEMCG_V1 config option, turned on by default +1 CONFIG_MEMCG1 should also work. > 4) making memcontrol-v1.c to compile only if CONFIG_MEMCG_V1 is set +1 > 5) putting unused struct memory_cgroup and task_struct members under > CONFIG_MEMCG_V1 as well. +1 > > 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? I think this would be great, to make it more obvious in memcontrol.c. For core cgroup code, we used cgroup1_foo(). Maybe name them all things like memcg1_update_tree() etc.? That's short and sweet while sticking out visually pretty well. > 2) Do we want to extend it beyond the memory controller? Should Could you please elaborate? ^_^ > 3) Is it better to use a new include/linux/memcontrol-v1.h instead of > mm/internal.h? Or mm/memcontrol-v1.h. mm/memcontrol-v1.h sounds good to me. > mm/memcontrol.c | 4121 ++++++++++++++++++++++--------------------------------------------------------------------------------------------------------------------------------- Lol, awesome.
