[Devel] Re: [PATCH] memory.min_usage

[Balbir Singh]

YAMAMOTO Takashi wrote:
> hi,
> 
> here's a patch to implement memory.min_usage,
> which controls the minimum memory usage for a cgroup.
> 
> it works similarly to mlock;
> global memory reclamation doesn't reclaim memory from
> cgroups whose memory usage is below the value.
> setting it too high is a dangerous operation.
> 
> it's against 2.6.24-rc3-mm2 + memory.swappiness patch i posted here yesterday.
> but it's logically independent from the swappiness patch.
> 

Hi,

I think it's a good approach, but we need to make the reclaim dependent
on priority. I think that if we stop reclaiming from a cgroup even
though there is high global pressure, it might be a bad idea.

> todo:
> - restrict non-root user's operation ragardless of owner of cgroupfs files?

Sorry, I don't understand this and I think using file permissions is a
good idea.

> - make oom killer aware of this?
> 

Yes, we might also need a memory controller version of

1. overcommit
2. oom_adj* parameters


> YAMAMOTO Takashi
> 
> 
> Signed-off-by: YAMAMOTO Takashi <yamamoto at valinux.co.jp>
> ---
> 
> --- linux-2.6.24-rc3-mm2-swappiness/include/linux/memcontrol.h.BACKUP2	2007-12-03 13:52:37.000000000 +0900
> +++ linux-2.6.24-rc3-mm2-swappiness/include/linux/memcontrol.h	2007-12-03 14:07:45.000000000 +0900
> @@ -47,6 +47,7 @@ extern int mem_cgroup_cache_charge(struc
>  					gfp_t gfp_mask);
>  int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
>  extern int mem_cgroup_swappiness(struct mem_cgroup *mem);
> +extern int mem_cgroup_canreclaim(struct page *page, struct mem_cgroup *mem);
> 
>  static inline struct mem_cgroup *mm_cgroup(const struct mm_struct *mm)
>  {
> --- linux-2.6.24-rc3-mm2-swappiness/mm/memcontrol.c.BACKUP2	2007-12-03 13:52:13.000000000 +0900
> +++ linux-2.6.24-rc3-mm2-swappiness/mm/memcontrol.c	2007-12-04 11:42:07.000000000 +0900
> @@ -134,6 +134,7 @@ struct mem_cgroup {
>  	unsigned long control_type;	/* control RSS or RSS+Pagecache */
>  	int	prev_priority;	/* for recording reclaim priority */
>  	unsigned int swappiness;	/* swappiness */
> +	unsigned long long min_usage; /* XXX should be a part of res_counter? */
>  	/*
>  	 * statistics.
>  	 */
> @@ -1096,6 +1097,22 @@ static u64 mem_cgroup_swappiness_read(st
>  	return mem->swappiness;
>  }
> 
> +static int mem_cgroup_min_usage_write(struct cgroup *cont, struct cftype *cft,
> +				       u64 val)
> +{
> +	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> +
> +	mem->min_usage = val;
> +	return 0;
> +}
> +
> +static u64 mem_cgroup_min_usage_read(struct cgroup *cont, struct cftype *cft)
> +{
> +	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> +
> +	return mem->min_usage;
> +}
> +
>  static struct cftype mem_cgroup_files[] = {
>  	{
>  		.name = "usage_in_bytes",
> @@ -1132,6 +1149,11 @@ static struct cftype mem_cgroup_files[] 
>  		.write_uint = mem_cgroup_swappiness_write,
>  		.read_uint = mem_cgroup_swappiness_read,
>  	},
> +	{
> +		.name = "min_usage_in_bytes",
> +		.write_uint = mem_cgroup_min_usage_write,
> +		.read_uint = mem_cgroup_min_usage_read,
> +	},
>  };
> 
>  /* XXX probably it's better to move try_to_free_mem_cgroup_pages to
> @@ -1142,6 +1164,36 @@ int mem_cgroup_swappiness(struct mem_cgr
>  	return mem->swappiness;
>  }
> 
> +int mem_cgroup_canreclaim(struct page *page, struct mem_cgroup *mem1)
> +{
> +	struct page_cgroup *pc;
> +	int result = 1;
> +
> +	if (mem1 != NULL)
> +		return 1;
> +
> +	lock_page_cgroup(page);
> +	pc = page_get_page_cgroup(page);
> +	if (pc) {
> +		struct mem_cgroup *mem2 = pc->mem_cgroup;
> +		unsigned long long min_usage;
> +
> +		BUG_ON(mem2 == NULL);
> +		min_usage = mem2->min_usage;
> +		if (min_usage != 0) {
> +			unsigned long flags;
> +
> +			spin_lock_irqsave(&mem2->res.lock, flags);
> +			if (mem2->res.usage <= min_usage)
> +				result = 0;
> +			spin_unlock_irqrestore(&mem2->res.lock, flags);
> +		}
> +	}
> +	unlock_page_cgroup(page);
> +
> +	return result;
> +}
> +
>  static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
>  {
>  	struct mem_cgroup_per_node *pn;
> --- linux-2.6.24-rc3-mm2-swappiness/mm/vmscan.c.BACKUP2	2007-12-03 13:52:22.000000000 +0900
> +++ linux-2.6.24-rc3-mm2-swappiness/mm/vmscan.c	2007-12-03 14:11:42.000000000 +0900
> @@ -531,6 +531,11 @@ static unsigned long shrink_page_list(st
>  					referenced && page_mapping_inuse(page))
>  			goto activate_locked;
> 
> +#ifdef CONFIG_CGROUP_MEM_CONT
> +		if (!mem_cgroup_canreclaim(page, sc->mem_cgroup))
> +			goto activate_locked;
> +#endif /* CONFIG_CGROUP_MEM_CONT */
> +
>  #ifdef CONFIG_SWAP
>  		/*
>  		 * Anonymous process memory has backing store?
> @@ -1122,6 +1127,12 @@ static void shrink_active_list(unsigned 
>  			list_add(&page->lru, &l_active);
>  			continue;
>  		}
> +#ifdef CONFIG_CGROUP_MEM_CONT
> +		if (!mem_cgroup_canreclaim(page, sc->mem_cgroup)) {
> +			list_add(&page->lru, &l_active);
> +			continue;
> +		}
> +#endif /* CONFIG_CGROUP_MEM_CONT */
>  		list_add(&page->lru, &l_inactive);
>  	}
> 
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-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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