Re: [PATCH 08/10] memcg: add cgroupfs interface to memcg dirty limits

[Ciju Rajan K <ciju@linux.vnet.ibm.com>]

Greg Thelen wrote:
> Add cgroupfs interface to memcg dirty page limits:
>   Direct write-out is controlled with:
>   - memory.dirty_ratio
>   - memory.dirty_bytes
>
>   Background write-out is controlled with:
>   - memory.dirty_background_ratio
>   - memory.dirty_background_bytes
>
> Signed-off-by: Andrea Righi <arighi@develer.com>
> Signed-off-by: Greg Thelen <gthelen@google.com>
> ---
>  mm/memcontrol.c |   89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 89 insertions(+), 0 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6ec2625..2d45a0a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -100,6 +100,13 @@ enum mem_cgroup_stat_index {
>  	MEM_CGROUP_STAT_NSTATS,
>  };
>
> +enum {
> +	MEM_CGROUP_DIRTY_RATIO,
> +	MEM_CGROUP_DIRTY_BYTES,
> +	MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
> +	MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
> +};
> +
>  struct mem_cgroup_stat_cpu {
>  	s64 count[MEM_CGROUP_STAT_NSTATS];
>  };
> @@ -4292,6 +4299,64 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
>  	return 0;
>  }
>
> +static u64 mem_cgroup_dirty_read(struct cgroup *cgrp, struct cftype *cft)
> +{
> +	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> +	bool root;
> +
> +	root = mem_cgroup_is_root(mem);
> +
> +	switch (cft->private) {
> +	case MEM_CGROUP_DIRTY_RATIO:
> +		return root ? vm_dirty_ratio : mem->dirty_param.dirty_ratio;
> +	case MEM_CGROUP_DIRTY_BYTES:
> +		return root ? vm_dirty_bytes : mem->dirty_param.dirty_bytes;
> +	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
> +		return root ? dirty_background_ratio :
> +			mem->dirty_param.dirty_background_ratio;
> +	case MEM_CGROUP_DIRTY_BACKGROUND_BYTES:
> +		return root ? dirty_background_bytes :
> +			mem->dirty_param.dirty_background_bytes;
> +	default:
> +		BUG();
> +	}
> +}
> +
> +static int
> +mem_cgroup_dirty_write(struct cgroup *cgrp, struct cftype *cft, u64 val)
> +{
> +	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> +	int type = cft->private;
> +
> +	if (cgrp->parent == NULL)
> +		return -EINVAL;
> +	if ((type == MEM_CGROUP_DIRTY_RATIO ||
> +	     type == MEM_CGROUP_DIRTY_BACKGROUND_RATIO) && val > 100)
> +		return -EINVAL;
> +	switch (type) {
> +	case MEM_CGROUP_DIRTY_RATIO:
> +		memcg->dirty_param.dirty_ratio = val;
> +		memcg->dirty_param.dirty_bytes = 0;
> +		break;
> +	case MEM_CGROUP_DIRTY_BYTES:
> +		memcg->dirty_param.dirty_bytes = val;
> +		memcg->dirty_param.dirty_ratio  = 0;
> +		break;
> +	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
> +		memcg->dirty_param.dirty_background_ratio = val;
> +		memcg->dirty_param.dirty_background_bytes = 0;
> +		break;
> +	case MEM_CGROUP_DIRTY_BACKGROUND_BYTES:
> +		memcg->dirty_param.dirty_background_bytes = val;
> +		memcg->dirty_param.dirty_background_ratio = 0;
> +		break;
> +	default:
> +		BUG();
> +		break;
> +	}
> +	return 0;
> +}
> +
>  static struct cftype mem_cgroup_files[] = {
>  	{
>  		.name = "usage_in_bytes",
> @@ -4355,6 +4420,30 @@ static struct cftype mem_cgroup_files[] = {
>  		.unregister_event = mem_cgroup_oom_unregister_event,
>  		.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
>  	},
> +	{
> +		.name = "dirty_ratio",
> +		.read_u64 = mem_cgroup_dirty_read,
> +		.write_u64 = mem_cgroup_dirty_write,
> +		.private = MEM_CGROUP_DIRTY_RATIO,
> +	},
> +	{
> +		.name = "dirty_bytes",
> +		.read_u64 = mem_cgroup_dirty_read,
> +		.write_u64 = mem_cgroup_dirty_write,
> +		.private = MEM_CGROUP_DIRTY_BYTES,
> +	},
> +	{
>   
Is it a good idea to rename "dirty_bytes" to "dirty_limit_in_bytes" ?
So that it can match with other memcg tunable naming convention.
We already have memory.memsw.limit_in_bytes, memory.limit_in_bytes, 
memory.soft_limit_in_bytes, etc.
> +		.name = "dirty_background_ratio",
> +		.read_u64 = mem_cgroup_dirty_read,
> +		.write_u64 = mem_cgroup_dirty_write,
> +		.private = MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
> +	},
> +	{
> +		.name = "dirty_background_bytes",
> +		.read_u64 = mem_cgroup_dirty_read,
> +		.write_u64 = mem_cgroup_dirty_write,
> +		.private = MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
>   
Similarly "dirty_background_bytes" to dirty_background_limit_in_bytes ?
> +	},
>  };
>
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
>   

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