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

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Message-ID: <xr93r5g5w0uc.fsf@ninji.mtv.corp.google.com>
Date:	Tue, 05 Oct 2010 00:33:15 -0700
From:	Greg Thelen <gthelen@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	containers@...ts.osdl.org, Andrea Righi <arighi@...eler.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH 08/10] memcg: add cgroupfs interface to memcg dirty limits

KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes:

> On Sun,  3 Oct 2010 23:58:03 -0700
> Greg Thelen <gthelen@...gle.com> 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@...eler.com>
>> Signed-off-by: Greg Thelen <gthelen@...gle.com>
>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> a question below.
>
>
>> ---
>>  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;
>
>
> Curious....is this same behavior as vm_dirty_ratio ?

I think this is same behavior as vm_dirty_ratio.  When vm_dirty_ratio is
changed then dirty_ratio_handler() will set vm_dirty_bytes=0.  When
vm_dirty_bytes is written dirty_bytes_handler() will set
vm_dirty_ratio=0.  So I think that the per-memcg dirty memory parameters
mimic the behavior of vm_dirty_ratio, vm_dirty_bytes and the other
global dirty parameters.

Am I missing your question?

> Thanks,
> -Kame
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