On Fri, Aug 12, 2022 at 06:09:26PM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Memory charged on group B abserved on belowing v2 hierarchy where we just would
> like to only have group E's memory be controlled and B's descendants compete freely
> for memory. This should be the consequences of unified hierarchy. Solve this by
> have the cgroup without valid memory css alloced use root_mem_cgroup instead of
> its ancestor's.
>
> A(subtree_control = memory) - B(subtree_control = NULL) - C()
> \ D()
> - E(subtree_control = memory) - F()
> \ G()
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
> kernel/cgroup/cgroup.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index 1779ccd..b29b3f6 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -533,6 +533,14 @@ static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
> * can't test the csses directly. Test ss_mask.
> */
> while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
> + /*
> + * charging to the parent cgroup which hasn't distribute
> + * memory control to its descendants doesn't make sense
> + * especially on cgroup v2, where the parent could be configured
> + * to use memory controller as its sibling want to use it
> + */
> + if (memory_cgrp_id == ss->id)
> + return &root_mem_cgroup->css;
This is gonna be a hard nack. A given cgroup always encompasses all the
resources consumed in its self-including subtree.
Thanks.
--
tejun
