[Devel] Re: [PATCH] memory.min_usage

[KAMEZAWA Hiroyuki]

On Tue,  4 Dec 2007 13:09:34 +0900 (JST)
yamamoto at valinux.co.jp (YAMAMOTO Takashi) wrote:

> hi,
> 
> here's a patch to implement memory.min_usage,
> which controls the minimum memory usage for a cgroup.
> 
Thanks.

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

I like 'only-for-root' user. or CAP_SYS_RESOURCE.

> - make oom killer aware of this?
>
For OOM-Killer, IMHO, no care is necessary (now).
This function can be considered as a kind of mlock(). A user can be aware of
memory usage.
But, we may need some logic/reason to request this function.

> +	unsigned long long min_usage; /* XXX should be a part of res_counter? */
>  	/*
Maybe res_counter is better. (Added CC: to Pavel Emelianov)


> +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;
> +}
> +

How about adding lock_and_get_page_cgroup(page)/put_page_cgroup() ?
==
struct page_cgroup *pc lock_and_get_page_cgroup(page)
{
	struct page_cgroup *pc;

	lock_page_cgroup(page);
	pc = page_get_page_cgroup(page);
	if (atomic_inc_not_zero(&pc->ref_cnt)) 
		pc = NULL;
	unlock_page_cgroup(page);
	return pc;
}

struct page_cgroup *pc put_page_cgroup(struct page_cgroup *pc)
{
	mem_cgroup_uncharge(pc);
}
==

BTW, how about add a status to res_counter ?
My (based on your) current patch uses watermark_state.

Maybe we can change it to be resource_state and show following status.

RES_STATE_HIT_LIMIT,
RES_STATE_ABOVE_HWATER,
RES_STATE_ABOVE_LWATER,
RES_STATE_STABLE, ?
RES_STATE_BELOW_MIN,

Useful ?


>  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 */
> +

Maybe 
==
if (scan_global_lru(sc) && !
    mem_cgroup_canreclaim(page, sc->mem-cgroup))
    goto activate_locked:
==



>  #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;
> +		}
here too.

Thanks,
-Kame

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