Re: [PATCH 4/4] Memory controller soft limit reclaim on contention (v5)

["KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>]

Balbir Singh wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-13
> 15:51:25]:
>
>> Balbir Singh wrote:
>> > Feature: Implement reclaim from groups over their soft limit
>> >
>> > From: Balbir Singh <balbir@linux.vnet.ibm.com>
>>
>> > +unsigned long mem_cgroup_soft_limit_reclaim(struct zonelist *zl,
>> gfp_t
>> > gfp_mask)
>> > +{
>> > +	unsigned long nr_reclaimed = 0;
>> > +	struct mem_cgroup *mem;
>> > +	unsigned long flags;
>> > +	unsigned long reclaimed;
>> > +
>> > +	/*
>> > +	 * This loop can run a while, specially if mem_cgroup's continuously
>> > +	 * keep exceeding their soft limit and putting the system under
>> > +	 * pressure
>> > +	 */
>> > +	do {
>> > +		mem = mem_cgroup_largest_soft_limit_node();
>> > +		if (!mem)
>> > +			break;
>> > +
>> > +		reclaimed = mem_cgroup_hierarchical_reclaim(mem, zl,
>> > +						gfp_mask,
>> > +						MEM_CGROUP_RECLAIM_SOFT);
>> > +		nr_reclaimed += reclaimed;
>> > +		spin_lock_irqsave(&memcg_soft_limit_tree_lock, flags);
>> > +		mem->usage_in_excess = res_counter_soft_limit_excess(&mem->res);
>> > +		__mem_cgroup_remove_exceeded(mem);
>> > +		if (mem->usage_in_excess)
>> > +			__mem_cgroup_insert_exceeded(mem);
>> > +		spin_unlock_irqrestore(&memcg_soft_limit_tree_lock, flags);
>> > +		css_put(&mem->css);
>> > +		cond_resched();
>> > +	} while (!nr_reclaimed);
>> > +	return nr_reclaimed;
>> > +}
>> > +
>>  Why do you never consider bad corner case....
>>  As I wrote many times, "order of global usage" doesn't mean the
>>  biggest user of memcg containes memory in zones which we want.
>>  So, please don't pust "mem" back to RB-tree if reclaimed is 0.
>>
>>  This routine seems toooo bad as v4.
>
> Are you talking about cases where a particular mem cgroup never
> allocated from a node? Thanks.. let me take a look at it
>
Using cpuset to test and limiting nodes for memory is an easy way,

Thanks,
-Kame

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