Re: [PATCH v2 04/11] kmem accounting basic infrastructure

[Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>]

(2012/08/09 22:01), Glauber Costa wrote:
> This patch adds the basic infrastructure for the accounting of the slab
> caches. To control that, the following files are created:
> 
>   * memory.kmem.usage_in_bytes
>   * memory.kmem.limit_in_bytes
>   * memory.kmem.failcnt
>   * memory.kmem.max_usage_in_bytes
> 
> They have the same meaning of their user memory counterparts. They
> reflect the state of the "kmem" res_counter.
> 
> The code is not enabled until a limit is set. This can be tested by the
> flag "kmem_accounted". This means that after the patch is applied, no
> behavioral changes exists for whoever is still using memcg to control
> their memory usage.
> 
> We always account to both user and kernel resource_counters. This
> effectively means that an independent kernel limit is in place when the
> limit is set to a lower value than the user memory. A equal or higher
> value means that the user limit will always hit first, meaning that kmem
> is effectively unlimited.
> 
> People who want to track kernel memory but not limit it, can set this
> limit to a very high number (like RESOURCE_MAX - 1page - that no one
> will ever hit, or equal to the user memory)
> 
> Signed-off-by: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
> CC: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
> CC: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>

Could you add  a patch for documentation of this new interface and a text
explaining the behavior of "kmem_accounting" ?

Hm, my concern is the difference of behavior between user page accounting and
kmem accounting...but this is how tcp-accounting is working.

Once you add Documentation, it's okay to add my Ack.

Thanks,
-Kame


> ---
>   mm/memcontrol.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b0e29f4..54e93de 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -273,6 +273,10 @@ struct mem_cgroup {
>   	};
>   
>   	/*
> +	 * the counter to account for kernel memory usage.
> +	 */
> +	struct res_counter kmem;
> +	/*
>   	 * Per cgroup active and inactive list, similar to the
>   	 * per zone LRU lists.
>   	 */
> @@ -287,6 +291,7 @@ struct mem_cgroup {
>   	 * Should the accounting and control be hierarchical, per subtree?
>   	 */
>   	bool use_hierarchy;
> +	bool kmem_accounted;
>   
>   	bool		oom_lock;
>   	atomic_t	under_oom;
> @@ -397,6 +402,7 @@ enum res_type {
>   	_MEM,
>   	_MEMSWAP,
>   	_OOM_TYPE,
> +	_KMEM,
>   };
>   
>   #define MEMFILE_PRIVATE(x, val)	((x) << 16 | (val))
> @@ -1499,6 +1505,10 @@ done:
>   		res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
>   		res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
>   		res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
> +	printk(KERN_INFO "kmem: usage %llukB, limit %llukB, failcnt %llu\n",
> +		res_counter_read_u64(&memcg->kmem, RES_USAGE) >> 10,
> +		res_counter_read_u64(&memcg->kmem, RES_LIMIT) >> 10,
> +		res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
>   
>   	mem_cgroup_print_oom_stat(memcg);
>   }
> @@ -4008,6 +4018,9 @@ static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
>   		else
>   			val = res_counter_read_u64(&memcg->memsw, name);
>   		break;
> +	case _KMEM:
> +		val = res_counter_read_u64(&memcg->kmem, name);
> +		break;
>   	default:
>   		BUG();
>   	}
> @@ -4046,8 +4059,23 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
>   			break;
>   		if (type == _MEM)
>   			ret = mem_cgroup_resize_limit(memcg, val);
> -		else
> +		else if (type == _MEMSWAP)
>   			ret = mem_cgroup_resize_memsw_limit(memcg, val);
> +		else if (type == _KMEM) {
> +			ret = res_counter_set_limit(&memcg->kmem, val);
> +			if (ret)
> +				break;
> +			/*
> +			 * Once enabled, can't be disabled. We could in theory
> +			 * disable it if we haven't yet created any caches, or
> +			 * if we can shrink them all to death.
> +			 *
> +			 * But it is not worth the trouble
> +			 */
> +			if (!memcg->kmem_accounted && val != RESOURCE_MAX)
> +				memcg->kmem_accounted = true;
> +		} else
> +			return -EINVAL;
>   		break;
>   	case RES_SOFT_LIMIT:
>   		ret = res_counter_memparse_write_strategy(buffer, &val);
> @@ -4113,12 +4141,16 @@ static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
>   	case RES_MAX_USAGE:
>   		if (type == _MEM)
>   			res_counter_reset_max(&memcg->res);
> +		else if (type == _KMEM)
> +			res_counter_reset_max(&memcg->kmem);
>   		else
>   			res_counter_reset_max(&memcg->memsw);
>   		break;
>   	case RES_FAILCNT:
>   		if (type == _MEM)
>   			res_counter_reset_failcnt(&memcg->res);
> +		else if (type == _KMEM)
> +			res_counter_reset_failcnt(&memcg->kmem);
>   		else
>   			res_counter_reset_failcnt(&memcg->memsw);
>   		break;
> @@ -4672,6 +4704,33 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
>   }
>   
>   #ifdef CONFIG_MEMCG_KMEM
> +static struct cftype kmem_cgroup_files[] = {
> +	{
> +		.name = "kmem.limit_in_bytes",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
> +		.write_string = mem_cgroup_write,
> +		.read = mem_cgroup_read,
> +	},
> +	{
> +		.name = "kmem.usage_in_bytes",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
> +		.read = mem_cgroup_read,
> +	},
> +	{
> +		.name = "kmem.failcnt",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
> +		.trigger = mem_cgroup_reset,
> +		.read = mem_cgroup_read,
> +	},
> +	{
> +		.name = "kmem.max_usage_in_bytes",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
> +		.trigger = mem_cgroup_reset,
> +		.read = mem_cgroup_read,
> +	},
> +	{},
> +};
> +
>   static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
>   {
>   	return mem_cgroup_sockets_init(memcg, ss);
> @@ -5015,6 +5074,12 @@ mem_cgroup_create(struct cgroup *cont)
>   		int cpu;
>   		enable_swap_cgroup();
>   		parent = NULL;
> +
> +#ifdef CONFIG_MEMCG_KMEM
> +		WARN_ON(cgroup_add_cftypes(&mem_cgroup_subsys,
> +					   kmem_cgroup_files));
> +#endif
> +
>   		if (mem_cgroup_soft_limit_tree_init())
>   			goto free_out;
>   		root_mem_cgroup = memcg;
> @@ -5033,6 +5098,7 @@ mem_cgroup_create(struct cgroup *cont)
>   	if (parent && parent->use_hierarchy) {
>   		res_counter_init(&memcg->res, &parent->res);
>   		res_counter_init(&memcg->memsw, &parent->memsw);
> +		res_counter_init(&memcg->kmem, &parent->kmem);
>   		/*
>   		 * We increment refcnt of the parent to ensure that we can
>   		 * safely access it on res_counter_charge/uncharge.
> @@ -5043,6 +5109,7 @@ mem_cgroup_create(struct cgroup *cont)
>   	} else {
>   		res_counter_init(&memcg->res, NULL);
>   		res_counter_init(&memcg->memsw, NULL);
> +		res_counter_init(&memcg->kmem, NULL);
>   	}
>   	memcg->last_scanned_node = MAX_NUMNODES;
>   	INIT_LIST_HEAD(&memcg->oom_notify);
>