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Date: Mon, 22 Sep 2014 16:07:34 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Vladimir Davydov <vdavydov@...allels.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Johannes Weiner <hannes@...xchg.org>,
Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH 2/2] memcg: move memcg_update_cache_size to slab_common.c
On Thu 18-09-14 19:50:20, Vladimir Davydov wrote:
> The only reason why this function lives in memcontrol.c is that it
> depends on memcg_caches_array_size. However, we can pass the new array
> size immediately to it instead of new_id+1 so that it will be free of
> any memcontrol.c dependencies.
>
> So let's move this function to slab_common.c and make it static.
Why?
besides that the patch does more code reshuffling which should be
documented. I have got lost a bit to be honest.
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: Christoph Lameter <cl@...ux.com>
> ---
> include/linux/memcontrol.h | 1 -
> mm/memcontrol.c | 114 ++++++++++++++------------------------------
> mm/slab_common.c | 30 +++++++++++-
> 3 files changed, 65 insertions(+), 80 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 4d17242eeff7..19df5d857411 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -440,7 +440,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
>
> int memcg_cache_id(struct mem_cgroup *memcg);
>
> -int memcg_update_cache_size(struct kmem_cache *s, int num_groups);
> void memcg_update_array_size(int num_groups);
>
> struct kmem_cache *
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b6bbb1e3e2ab..9431024e490c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -646,11 +646,13 @@ int memcg_limited_groups_array_size;
> struct static_key memcg_kmem_enabled_key;
> EXPORT_SYMBOL(memcg_kmem_enabled_key);
>
> +static void memcg_free_cache_id(int id);
> +
> static void disarm_kmem_keys(struct mem_cgroup *memcg)
> {
> if (memcg_kmem_is_active(memcg)) {
> static_key_slow_dec(&memcg_kmem_enabled_key);
> - ida_simple_remove(&kmem_limited_groups, memcg->kmemcg_id);
> + memcg_free_cache_id(memcg->kmemcg_id);
> }
> /*
> * This check can't live in kmem destruction function,
> @@ -2892,19 +2894,45 @@ int memcg_cache_id(struct mem_cgroup *memcg)
> return memcg ? memcg->kmemcg_id : -1;
> }
>
> -static size_t memcg_caches_array_size(int num_groups)
> +static int memcg_alloc_cache_id(void)
> {
> - ssize_t size;
> - if (num_groups <= 0)
> - return 0;
> + int id, size;
> + int err;
> +
> + id = ida_simple_get(&kmem_limited_groups,
> + 0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
> + if (id < 0)
> + return id;
>
> - size = 2 * num_groups;
> + if (id < memcg_limited_groups_array_size)
> + return id;
> +
> + /*
> + * There's no space for the new id in memcg_caches arrays,
> + * so we have to grow them.
> + */
> +
> + size = 2 * (id + 1);
> if (size < MEMCG_CACHES_MIN_SIZE)
> size = MEMCG_CACHES_MIN_SIZE;
> else if (size > MEMCG_CACHES_MAX_SIZE)
> size = MEMCG_CACHES_MAX_SIZE;
>
> - return size;
> + mutex_lock(&memcg_slab_mutex);
> + err = memcg_update_all_caches(size);
> + mutex_unlock(&memcg_slab_mutex);
> +
> + if (err) {
> + ida_simple_remove(&kmem_limited_groups, id);
> + return err;
> + }
> + return id;
> +
> +}
> +
> +static void memcg_free_cache_id(int id)
> +{
> + ida_simple_remove(&kmem_limited_groups, id);
> }
>
> /*
> @@ -2914,60 +2942,7 @@ static size_t memcg_caches_array_size(int num_groups)
> */
> void memcg_update_array_size(int num)
> {
> - if (num > memcg_limited_groups_array_size)
> - memcg_limited_groups_array_size = memcg_caches_array_size(num);
> -}
> -
> -int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
> -{
> - struct memcg_cache_params *cur_params = s->memcg_params;
> -
> - VM_BUG_ON(!is_root_cache(s));
> -
> - if (num_groups > memcg_limited_groups_array_size) {
> - int i;
> - struct memcg_cache_params *new_params;
> - ssize_t size = memcg_caches_array_size(num_groups);
> -
> - size *= sizeof(void *);
> - size += offsetof(struct memcg_cache_params, memcg_caches);
> -
> - new_params = kzalloc(size, GFP_KERNEL);
> - if (!new_params)
> - return -ENOMEM;
> -
> - new_params->is_root_cache = true;
> -
> - /*
> - * There is the chance it will be bigger than
> - * memcg_limited_groups_array_size, if we failed an allocation
> - * in a cache, in which case all caches updated before it, will
> - * have a bigger array.
> - *
> - * But if that is the case, the data after
> - * memcg_limited_groups_array_size is certainly unused
> - */
> - for (i = 0; i < memcg_limited_groups_array_size; i++) {
> - if (!cur_params->memcg_caches[i])
> - continue;
> - new_params->memcg_caches[i] =
> - cur_params->memcg_caches[i];
> - }
> -
> - /*
> - * Ideally, we would wait until all caches succeed, and only
> - * then free the old one. But this is not worth the extra
> - * pointer per-cache we'd have to have for this.
> - *
> - * It is not a big deal if some caches are left with a size
> - * bigger than the others. And all updates will reset this
> - * anyway.
> - */
> - rcu_assign_pointer(s->memcg_params, new_params);
> - if (cur_params)
> - kfree_rcu(cur_params, rcu_head);
> - }
> - return 0;
> + memcg_limited_groups_array_size = num;
> }
>
> static void memcg_register_cache(struct mem_cgroup *memcg,
> @@ -4167,23 +4142,12 @@ static int __memcg_activate_kmem(struct mem_cgroup *memcg,
> if (err)
> goto out;
>
> - memcg_id = ida_simple_get(&kmem_limited_groups,
> - 0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
> + memcg_id = memcg_alloc_cache_id();
> if (memcg_id < 0) {
> err = memcg_id;
> goto out;
> }
>
> - /*
> - * Make sure we have enough space for this cgroup in each root cache's
> - * memcg_params.
> - */
> - mutex_lock(&memcg_slab_mutex);
> - err = memcg_update_all_caches(memcg_id + 1);
> - mutex_unlock(&memcg_slab_mutex);
> - if (err)
> - goto out_rmid;
> -
> memcg->kmemcg_id = memcg_id;
> INIT_LIST_HEAD(&memcg->memcg_slab_caches);
>
> @@ -4204,10 +4168,6 @@ static int __memcg_activate_kmem(struct mem_cgroup *memcg,
> out:
> memcg_resume_kmem_account();
> return err;
> -
> -out_rmid:
> - ida_simple_remove(&kmem_limited_groups, memcg_id);
> - goto out;
> }
>
> static int memcg_activate_kmem(struct mem_cgroup *memcg,
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 9c29ba792368..800314e2a075 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -120,6 +120,33 @@ static void memcg_free_cache_params(struct kmem_cache *s)
> kfree(s->memcg_params);
> }
>
> +static int memcg_update_cache_params(struct kmem_cache *s, int num_memcgs)
> +{
> + int size;
> + struct memcg_cache_params *new_params, *cur_params;
> +
> + BUG_ON(!is_root_cache(s));
> +
> + size = offsetof(struct memcg_cache_params, memcg_caches);
> + size += num_memcgs * sizeof(void *);
> +
> + new_params = kzalloc(size, GFP_KERNEL);
> + if (!new_params)
> + return -ENOMEM;
> +
> + cur_params = s->memcg_params;
> + memcpy(new_params->memcg_caches, cur_params->memcg_caches,
> + memcg_limited_groups_array_size * sizeof(void *));
> +
> + new_params->is_root_cache = true;
> +
> + rcu_assign_pointer(s->memcg_params, new_params);
> + if (cur_params)
> + kfree_rcu(cur_params, rcu_head);
> +
> + return 0;
> +}
> +
> int memcg_update_all_caches(int num_memcgs)
> {
> struct kmem_cache *s;
> @@ -130,9 +157,8 @@ int memcg_update_all_caches(int num_memcgs)
> if (!is_root_cache(s))
> continue;
>
> - ret = memcg_update_cache_size(s, num_memcgs);
> + ret = memcg_update_cache_params(s, num_memcgs);
> /*
> - * See comment in memcontrol.c, memcg_update_cache_size:
> * Instead of freeing the memory, we'll just leave the caches
> * up to this point in an updated state.
> */
> --
> 1.7.10.4
>
--
Michal Hocko
SUSE Labs
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