| Message ID | 06505918-3b8a-0ad5-5951-89ecb510138e@openvz.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | memcg: accounting for objects allocated by mkdir cgroup | expand |
On Mon, May 30, 2022 at 7:27 PM Vasily Averin <vvs@openvz.org> wrote: > > If enabled in config, alloc_rt_sched_group() is called for each new > cpu cgroup and allocates a huge (~1700 bytes) percpu struct rt_rq. > This significantly exceeds the size of the percpu allocation in the > common part of cgroup creation. > > Memory allocated during new cpu cgroup creation > (with enabled RT_GROUP_SCHED): > common part: ~11Kb + 318 bytes percpu > cpu cgroup: ~2.5Kb + ~2800 bytes percpu > > Accounting for this memory helps to avoid misuse inside memcg-limited > containers. > > Signed-off-by: Vasily Averin <vvs@openvz.org> Acked-by: Muchun Song <songmuchun@bytedance.com> Thanks.
Below is tracing results of mkdir /sys/fs/cgroup/vvs.test on 4cpu VM with Fedora and self-complied upstream kernel. The calculations are not precise, it depends on kernel config options, number of cpus, enabled controllers, ignores possible page allocations etc. However this is enough to clarify the general situation. All allocations are splited into: - common part, always called for each cgroup type - per-cgroup allocations In each group we consider 2 corner cases: - usual allocations, important for 1-2 CPU nodes/Vms - percpu allocations, important for 'big irons' common part: ~11Kb + 318 bytes percpu memcg: ~17Kb + 4692 bytes percpu cpu: ~2.5Kb + 1036 bytes percpu cpuset: ~3Kb + 12 bytes percpu blkcg: ~3Kb + 12 bytes percpu pid: ~1.5Kb + 12 bytes percpu perf: ~320b + 60 bytes percpu ------------------------------------------- total: ~38Kb + 6142 bytes percpu currently accounted: 4668 bytes percpu - it's important to account usual allocations called in common part, because almost all of cgroup-specific allocations are small. One exception here is memory cgroup, it allocates a few huge objects that should be accounted. - Percpu allocation called in common part, in memcg and cpu cgroups should be accounted, rest ones are small an can be ignored. - KERNFS objects are allocated both in common part and in most of cgroups Details can be found here: https://lore.kernel.org/all/d28233ee-bccb-7bc3-c2ec-461fd7f95e6a@openvz.org/ I checked other cgroups types was found that they all can be ignored. Additionally I found allocation of struct rt_rq called in cpu cgroup if CONFIG_RT_GROUP_SCHED was enabled, it allocates huge (~1700 bytes) percpu structure and should be accounted too. v2: 1) re-split to simplify possible bisect, re-ordered 2) added accounting for percpu psi_group_cpu and cgroup_rstat_cpu, allocated in common part 3) added accounting for percpu allocation of struct rt_rq (actual if CONFIG_RT_GROUP_SCHED is enabled) 4) improved patches descriptions Vasily Averin (9): memcg: enable accounting for struct cgroup memcg: enable accounting for kernfs nodes memcg: enable accounting for kernfs iattrs memcg: enable accounting for struct simple_xattr memcg: enable accounting for percpu allocation of struct psi_group_cpu memcg: enable accounting for percpu allocation of struct cgroup_rstat_cpu memcg: enable accounting for large allocations in mem_cgroup_css_alloc memcg: enable accounting for allocations in alloc_fair_sched_group memcg: enable accounting for percpu allocation of struct rt_rq fs/kernfs/mount.c | 6 ++++-- fs/xattr.c | 2 +- kernel/cgroup/cgroup.c | 2 +- kernel/cgroup/rstat.c | 3 ++- kernel/sched/fair.c | 4 ++-- kernel/sched/psi.c | 3 ++- kernel/sched/rt.c | 2 +- mm/memcontrol.c | 4 ++-- 8 files changed, 15 insertions(+), 11 deletions(-)