Subject: Re: [PATCH v3 1/7] Basic kernel memory functionality for the Memory Controller

From: Glauber Costa <[email-masked]>
Date: Tue, 20 Sep 2011 23:23:30 -0300

Hi people,

Any insights on this series?
Kame, is it inline with your expectations ?

Thank you all

On 09/18/2011 09:56 PM, Glauber Costa wrote:
> This patch lays down the foundation for the kernel memory component
> of the Memory Controller.
>
> As of today, I am only laying down the following files:
>
>   * memory.independent_kmem_limit
>   * memory.kmem.limit_in_bytes (currently ignored)
>   * memory.kmem.usage_in_bytes (always zero)
>
> Signed-off-by: Glauber Costa<[email-masked]>
> CC: Paul Menage<[email-masked]>
> CC: Greg Thelen<[email-masked]>
> ---
>   Documentation/cgroups/memory.txt |   30 +++++++++-
>   init/Kconfig                     |   11 ++++
>   mm/memcontrol.c                  |  115 ++++++++++++++++++++++++++++++++++++--
>   3 files changed, 148 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> index 6f3c598..6f1954a 100644
> --- a/Documentation/cgroups/memory.txt
> +++ b/Documentation/cgroups/memory.txt
> @@ -44,8 +44,9 @@ Features:
>    - oom-killer disable knob and oom-notifier
>    - Root cgroup has no limit controls.
>
> - Kernel memory and Hugepages are not under control yet. We just manage
> - pages on LRU. To add more controls, we have to take care of performance.
> + Hugepages is not under control yet. We just manage pages on LRU. To add more
> + controls, we have to take care of performance. Kernel memory support is work
> + in progress, and the current version provides basically functionality.
>
>   Brief summary of control files.
>
> @@ -56,8 +57,11 @@ Brief summary of control files.
>   				 (See 5.5 for details)
>    memory.memsw.usage_in_bytes	 # show current res_counter usage for memory+Swap
>   				 (See 5.5 for details)
> + memory.kmem.usage_in_bytes	 # show current res_counter usage for kmem only.
> +				 (See 2.7 for details)
>    memory.limit_in_bytes		 # set/show limit of memory usage
>    memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage
> + memory.kmem.limit_in_bytes	 # if allowed, set/show limit of kernel memory
>    memory.failcnt			 # show the number of memory usage hits limits
>    memory.memsw.failcnt		 # show the number of memory+Swap hits limits
>    memory.max_usage_in_bytes	 # show max memory usage recorded
> @@ -72,6 +76,9 @@ Brief summary of control files.
>    memory.oom_control		 # set/show oom controls.
>    memory.numa_stat		 # show the number of memory usage per numa node
>
> + memory.independent_kmem_limit	 # select whether or not kernel memory limits are
> +				   independent of user limits
> +
>   1. History
>
>   The memory controller has a long history. A request for comments for the memory
> @@ -255,6 +262,25 @@ When oom event notifier is registered, event will be delivered.
>     per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
>     zone->lru_lock, it has no lock of its own.
>
> +2.7 Kernel Memory Extension (CONFIG_CGROUP_MEM_RES_CTLR_KMEM)
> +
> + With the Kernel memory extension, the Memory Controller is able to limit
> +the amount of kernel memory used by the system. Kernel memory is fundamentally
> +different than user memory, since it can't be swapped out, which makes it
> +possible to DoS the system by consuming too much of this precious resource.
> +Kernel memory limits are not imposed for the root cgroup.
> +
> +Memory limits as specified by the standard Memory Controller may or may not
> +take kernel memory into consideration. This is achieved through the file
> +memory.independent_kmem_limit. A Value different than 0 will allow for kernel
> +memory to be controlled separately.
> +
> +When kernel memory limits are not independent, the limit values set in
> +memory.kmem files are ignored.
> +
> +Currently no soft limit is implemented for kernel memory. It is future work
> +to trigger slab reclaim when those limits are reached.
> +
>   3. User Interface
>
>   0. Configuration
> diff --git a/init/Kconfig b/init/Kconfig
> index d627783..49e5839 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -689,6 +689,17 @@ config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
>   	  For those who want to have the feature enabled by default should
>   	  select this option (if, for some reason, they need to disable it
>   	  then swapaccount=0 does the trick).
> +config CGROUP_MEM_RES_CTLR_KMEM
> +	bool "Memory Resource Controller Kernel Memory accounting"
> +	depends on CGROUP_MEM_RES_CTLR
> +	default y
> +	help
> +	  The Kernel Memory extension for Memory Resource Controller can limit
> +	  the amount of memory used by kernel objects in the system. Those are
> +	  fundamentally different from the entities handled by the standard
> +	  Memory Controller, which are page-based, and can be swapped. Users of
> +	  the kmem extension can use it to guarantee that no group of processes
> +	  will ever exhaust kernel resources alone.
>
>   config CGROUP_PERF
>   	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ebd1e86..d32e931 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -73,7 +73,11 @@ static int really_do_swap_account __initdata = 0;
>   #define do_swap_account		(0)
>   #endif
>
> -
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +int do_kmem_account __read_mostly = 1;
> +#else
> +#define do_kmem_account		0
> +#endif
>   /*
>    * Statistics for memory cgroup.
>    */
> @@ -270,6 +274,10 @@ struct mem_cgroup {
>   	 */
>   	struct res_counter memsw;
>   	/*
> +	 * the counter to account for kmem usage.
> +	 */
> +	struct res_counter kmem;
> +	/*
>   	 * Per cgroup active and inactive list, similar to the
>   	 * per zone LRU lists.
>   	 */
> @@ -321,6 +329,11 @@ struct mem_cgroup {
>   	 */
>   	unsigned long 	move_charge_at_immigrate;
>   	/*
> +	 * Should kernel memory limits be stabilished independently
> +	 * from user memory ?
> +	 */
> +	int		kmem_independent;
> +	/*
>   	 * percpu counter.
>   	 */
>   	struct mem_cgroup_stat_cpu *stat;
> @@ -388,9 +401,14 @@ enum charge_type {
>   };
>
>   /* for encoding cft->private value on file */
> -#define _MEM			(0)
> -#define _MEMSWAP		(1)
> -#define _OOM_TYPE		(2)
> +
> +enum mem_type {
> +	_MEM = 0,
> +	_MEMSWAP,
> +	_OOM_TYPE,
> +	_KMEM,
> +};
> +
>   #define MEMFILE_PRIVATE(x, val)	(((x)<<  16) | (val))
>   #define MEMFILE_TYPE(val)	(((val)>>  16)&  0xffff)
>   #define MEMFILE_ATTR(val)	((val)&  0xffff)
> @@ -3943,10 +3961,15 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
>   	u64 val;
>
>   	if (!mem_cgroup_is_root(mem)) {
> +		val = 0;
> +		if (!mem->kmem_independent)
> +			val = res_counter_read_u64(&mem->kmem, RES_USAGE);
>   		if (!swap)
> -			return res_counter_read_u64(&mem->res, RES_USAGE);
> +			val += res_counter_read_u64(&mem->res, RES_USAGE);
>   		else
> -			return res_counter_read_u64(&mem->memsw, RES_USAGE);
> +			val += res_counter_read_u64(&mem->memsw, RES_USAGE);
> +
> +		return val;
>   	}
>
>   	val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
> @@ -3979,6 +4002,10 @@ static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
>   		else
>   			val = res_counter_read_u64(&mem->memsw, name);
>   		break;
> +	case _KMEM:
> +		val = res_counter_read_u64(&mem->kmem, name);
> +		break;
> +
>   	default:
>   		BUG();
>   		break;
> @@ -4756,6 +4783,21 @@ static int mem_cgroup_reset_vmscan_stat(struct cgroup *cgrp,
>   	return 0;
>   }
>
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +static u64 kmem_limit_independent_read(struct cgroup *cont, struct cftype *cft)
> +{
> +	return mem_cgroup_from_cont(cont)->kmem_independent;
> +}
> +
> +static int kmem_limit_independent_write(struct cgroup *cont, struct cftype *cft,
> +					u64 val)
> +{
> +	cgroup_lock();
> +	mem_cgroup_from_cont(cont)->kmem_independent = !!val;
> +	cgroup_unlock();
> +	return 0;
> +}
> +#endif
>
>   static struct cftype mem_cgroup_files[] = {
>   	{
> @@ -4877,6 +4919,47 @@ static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
>   }
>   #endif
>
> +
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +static struct cftype kmem_cgroup_files[] = {
> +	{
> +		.name = "independent_kmem_limit",
> +		.read_u64 = kmem_limit_independent_read,
> +		.write_u64 = kmem_limit_independent_write,
> +	},
> +	{
> +		.name = "kmem.usage_in_bytes",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
> +		.read_u64 = mem_cgroup_read,
> +	},
> +	{
> +		.name = "kmem.limit_in_bytes",
> +		.private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
> +		.read_u64 = mem_cgroup_read,
> +	},
> +};
> +
> +static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
> +{
> +	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> +	int ret = 0;
> +
> +	if (!do_kmem_account)
> +		return 0;
> +
> +	if (!mem_cgroup_is_root(mem))
> +		ret = cgroup_add_files(cont, ss, kmem_cgroup_files,
> +					ARRAY_SIZE(kmem_cgroup_files));
> +	return ret;
> +};
> +
> +#else
> +static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
> +{
> +	return 0;
> +}
> +#endif
> +
>   static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
>   {
>   	struct mem_cgroup_per_node *pn;
> @@ -5075,6 +5158,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>   	if (parent&&  parent->use_hierarchy) {
>   		res_counter_init(&mem->res,&parent->res);
>   		res_counter_init(&mem->memsw,&parent->memsw);
> +		res_counter_init(&mem->kmem,&parent->kmem);
>   		/*
>   		 * We increment refcnt of the parent to ensure that we can
>   		 * safely access it on res_counter_charge/uncharge.
> @@ -5085,6 +5169,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>   	} else {
>   		res_counter_init(&mem->res, NULL);
>   		res_counter_init(&mem->memsw, NULL);
> +		res_counter_init(&mem->kmem, NULL);
>   	}
>   	mem->last_scanned_child = 0;
>   	mem->last_scanned_node = MAX_NUMNODES;
> @@ -5129,6 +5214,10 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
>
>   	if (!ret)
>   		ret = register_memsw_files(cont, ss);
> +
> +	if (!ret)
> +		ret = register_kmem_files(cont, ss);
> +
>   	return ret;
>   }
>
> @@ -5665,3 +5754,17 @@ static int __init enable_swap_account(char *s)
>   __setup("swapaccount=", enable_swap_account);
>
>   #endif
> +
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +static int __init disable_kmem_account(char *s)
> +{
> +	/* consider enabled if no parameter or 1 is given */
> +	if (!strcmp(s, "1"))
> +		do_kmem_account = 1;
> +	else if (!strcmp(s, "0"))
> +		do_kmem_account = 0;
> +	return 1;
> +}
> +__setup("kmemaccount=", disable_kmem_account);
> +
> +#endif

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