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SubjectRe: [PATCH v2 04/11] kmem accounting basic infrastructure
(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@parallels.com>
> CC: Michal Hocko <mhocko@suse.cz>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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);
>




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