Re: [PATCH mm v2 6/9] memcg: enable accounting for percpu allocation of struct cgroup_rstat_cpu

[Vasily Averin]

On 5/21/22 19:38, Vasily Averin wrote:
> struct cgroup_rstat_cpu is percpu allocated for each new cgroup and
> can consume a significant portion of all allocated memory on nodes
> with a large number of CPUs.
> 
> Common part of the cgroup creation:
> Allocs  Alloc   $1*$2   Sum	Allocation
> number  size
> --------------------------------------------
> 16  ~   352     5632    5632    KERNFS
> 1   +   4096    4096    9728    (cgroup_mkdir+0xe4)
> 1       584     584     10312   (radix_tree_node_alloc.constprop.0+0x89)
> 1       192     192     10504   (__d_alloc+0x29)
> 2       72      144     10648   (avc_alloc_node+0x27)
> 2       64      128     10776   (percpu_ref_init+0x6a)
> 1       64      64      10840   (memcg_list_lru_alloc+0x21a)
> percpu:
> 1   +   192     192     192     call_site=psi_cgroup_alloc+0x1e
> 1   +   96      96      288     call_site=cgroup_rstat_init+0x5f
> 2       12      24      312     call_site=percpu_ref_init+0x23
> 1       6       6       318     call_site=__percpu_counter_init+0x22
> 
>  '+' -- to be accounted,
>  '~' -- partially accounted
> 
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxx>
> ---
>  kernel/cgroup/rstat.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> index 24b5c2ab5598..f76cb63ae2e0 100644
> --- a/kernel/cgroup/rstat.c
> +++ b/kernel/cgroup/rstat.c
> @@ -257,7 +257,8 @@ int cgroup_rstat_init(struct cgroup *cgrp)
>  
>  	/* the root cgrp has rstat_cpu preallocated */
>  	if (!cgrp->rstat_cpu) {
> -		cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
> +		cgrp->rstat_cpu = alloc_percpu_gfp(struct cgroup_rstat_cpu
"," was lost here
> +						   GFP_KERNEL_ACCOUNT);
>  		if (!cgrp->rstat_cpu)
>  			return -ENOMEM;
>  	}