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Date: Fri, 29 Jan 2021 09:11:12 -0800
From: Yang Shi <shy828301@...il.com>
To: Kirill Tkhai <ktkhai@...tuozzo.com>
Cc: Roman Gushchin <guro@...com>, Shakeel Butt <shakeelb@...gle.com>,
Dave Chinner <david@...morbit.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux MM <linux-mm@...ck.org>,
Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v5 PATCH 02/11] mm: vmscan: consolidate shrinker_maps handling code
On Fri, Jan 29, 2021 at 6:34 AM Kirill Tkhai <ktkhai@...tuozzo.com> wrote:
>
> On 28.01.2021 02:33, Yang Shi wrote:
> > The shrinker map management is not purely memcg specific, it is at the intersection
> > between memory cgroup and shrinkers. It's allocation and assignment of a structure,
> > and the only memcg bit is the map is being stored in a memcg structure. So move the
> > shrinker_maps handling code into vmscan.c for tighter integration with shrinker code,
> > and remove the "memcg_" prefix. There is no functional change.
> >
> > Signed-off-by: Yang Shi <shy828301@...il.com>
> > ---
> > include/linux/memcontrol.h | 12 ++--
> > mm/huge_memory.c | 4 +-
> > mm/list_lru.c | 6 +-
> > mm/memcontrol.c | 130 +------------------------------------
> > mm/vmscan.c | 130 ++++++++++++++++++++++++++++++++++++-
> > 5 files changed, 142 insertions(+), 140 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index eeb0b52203e9..0ee2924991fb 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -1581,10 +1581,10 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
> > return false;
> > }
> >
> > -extern int memcg_expand_shrinker_maps(int new_id);
> > -
> > -extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
> > - int nid, int shrinker_id);
> > +extern int alloc_shrinker_maps(struct mem_cgroup *memcg);
> > +extern void free_shrinker_maps(struct mem_cgroup *memcg);
> > +extern void set_shrinker_bit(struct mem_cgroup *memcg,
> > + int nid, int shrinker_id);
> > #else
> > #define mem_cgroup_sockets_enabled 0
> > static inline void mem_cgroup_sk_alloc(struct sock *sk) { };
> > @@ -1594,8 +1594,8 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
> > return false;
> > }
> >
> > -static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
> > - int nid, int shrinker_id)
> > +static inline void set_shrinker_bit(struct mem_cgroup *memcg,
> > + int nid, int shrinker_id)
> > {
> > }
> > #endif
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 9237976abe72..05190d7f32ae 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2823,8 +2823,8 @@ void deferred_split_huge_page(struct page *page)
> > ds_queue->split_queue_len++;
> > #ifdef CONFIG_MEMCG
> > if (memcg)
> > - memcg_set_shrinker_bit(memcg, page_to_nid(page),
> > - deferred_split_shrinker.id);
> > + set_shrinker_bit(memcg, page_to_nid(page),
> > + deferred_split_shrinker.id);
> > #endif
> > }
> > spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
> > diff --git a/mm/list_lru.c b/mm/list_lru.c
> > index fe230081690b..628030fa5f69 100644
> > --- a/mm/list_lru.c
> > +++ b/mm/list_lru.c
> > @@ -125,8 +125,8 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
> > list_add_tail(item, &l->list);
> > /* Set shrinker bit if the first element was added */
> > if (!l->nr_items++)
> > - memcg_set_shrinker_bit(memcg, nid,
> > - lru_shrinker_id(lru));
> > + set_shrinker_bit(memcg, nid,
> > + lru_shrinker_id(lru));
> > nlru->nr_items++;
> > spin_unlock(&nlru->lock);
> > return true;
> > @@ -548,7 +548,7 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
> >
> > if (src->nr_items) {
> > dst->nr_items += src->nr_items;
> > - memcg_set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
> > + set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
> > src->nr_items = 0;
> > }
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index e2de77b5bcc2..f5c9a0d2160b 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -397,130 +397,6 @@ DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
> > EXPORT_SYMBOL(memcg_kmem_enabled_key);
> > #endif
> >
> > -static int memcg_shrinker_map_size;
> > -static DEFINE_MUTEX(memcg_shrinker_map_mutex);
> > -
> > -static void memcg_free_shrinker_map_rcu(struct rcu_head *head)
> > -{
> > - kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > -}
> > -
> > -static int memcg_expand_one_shrinker_map(struct mem_cgroup *memcg,
> > - int size, int old_size)
> > -{
> > - struct memcg_shrinker_map *new, *old;
> > - int nid;
> > -
> > - lockdep_assert_held(&memcg_shrinker_map_mutex);
> > -
> > - for_each_node(nid) {
> > - old = rcu_dereference_protected(
> > - mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
> > - /* Not yet online memcg */
> > - if (!old)
> > - return 0;
> > -
> > - new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
> > - if (!new)
> > - return -ENOMEM;
> > -
> > - /* Set all old bits, clear all new bits */
> > - memset(new->map, (int)0xff, old_size);
> > - memset((void *)new->map + old_size, 0, size - old_size);
> > -
> > - rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > - call_rcu(&old->rcu, memcg_free_shrinker_map_rcu);
> > - }
> > -
> > - return 0;
> > -}
> > -
> > -static void memcg_free_shrinker_maps(struct mem_cgroup *memcg)
> > -{
> > - struct mem_cgroup_per_node *pn;
> > - struct memcg_shrinker_map *map;
> > - int nid;
> > -
> > - if (mem_cgroup_is_root(memcg))
> > - return;
> > -
> > - for_each_node(nid) {
> > - pn = mem_cgroup_nodeinfo(memcg, nid);
> > - map = rcu_dereference_protected(pn->shrinker_map, true);
> > - if (map)
> > - kvfree(map);
> > - rcu_assign_pointer(pn->shrinker_map, NULL);
> > - }
> > -}
> > -
> > -static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg)
> > -{
> > - struct memcg_shrinker_map *map;
> > - int nid, size, ret = 0;
> > -
> > - if (mem_cgroup_is_root(memcg))
> > - return 0;
> > -
> > - mutex_lock(&memcg_shrinker_map_mutex);
> > - size = memcg_shrinker_map_size;
> > - for_each_node(nid) {
> > - map = kvzalloc_node(sizeof(*map) + size, GFP_KERNEL, nid);
> > - if (!map) {
> > - memcg_free_shrinker_maps(memcg);
> > - ret = -ENOMEM;
> > - break;
> > - }
> > - rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, map);
> > - }
> > - mutex_unlock(&memcg_shrinker_map_mutex);
> > -
> > - return ret;
> > -}
> > -
> > -int memcg_expand_shrinker_maps(int new_id)
> > -{
> > - int size, old_size, ret = 0;
> > - struct mem_cgroup *memcg;
> > -
> > - size = DIV_ROUND_UP(new_id + 1, BITS_PER_LONG) * sizeof(unsigned long);
> > - old_size = memcg_shrinker_map_size;
> > - if (size <= old_size)
> > - return 0;
> > -
> > - mutex_lock(&memcg_shrinker_map_mutex);
> > - if (!root_mem_cgroup)
> > - goto unlock;
> > -
> > - for_each_mem_cgroup(memcg) {
> > - if (mem_cgroup_is_root(memcg))
> > - continue;
> > - ret = memcg_expand_one_shrinker_map(memcg, size, old_size);
> > - if (ret) {
> > - mem_cgroup_iter_break(NULL, memcg);
> > - goto unlock;
> > - }
> > - }
> > -unlock:
> > - if (!ret)
> > - memcg_shrinker_map_size = size;
> > - mutex_unlock(&memcg_shrinker_map_mutex);
> > - return ret;
> > -}
> > -
> > -void memcg_set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
> > -{
> > - if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
> > - struct memcg_shrinker_map *map;
> > -
> > - rcu_read_lock();
> > - map = rcu_dereference(memcg->nodeinfo[nid]->shrinker_map);
> > - /* Pairs with smp mb in shrink_slab() */
> > - smp_mb__before_atomic();
> > - set_bit(shrinker_id, map->map);
> > - rcu_read_unlock();
> > - }
> > -}
> > -
> > /**
> > * mem_cgroup_css_from_page - css of the memcg associated with a page
> > * @page: page of interest
> > @@ -5370,11 +5246,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
> > struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> >
> > /*
> > - * A memcg must be visible for memcg_expand_shrinker_maps()
> > + * A memcg must be visible for expand_shrinker_maps()
> > * by the time the maps are allocated. So, we allocate maps
> > * here, when for_each_mem_cgroup() can't skip it.
> > */
> > - if (memcg_alloc_shrinker_maps(memcg)) {
> > + if (alloc_shrinker_maps(memcg)) {
> > mem_cgroup_id_remove(memcg);
> > return -ENOMEM;
> > }
> > @@ -5438,7 +5314,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
> > vmpressure_cleanup(&memcg->vmpressure);
> > cancel_work_sync(&memcg->high_work);
> > mem_cgroup_remove_from_trees(memcg);
> > - memcg_free_shrinker_maps(memcg);
> > + free_shrinker_maps(memcg);
> > memcg_free_kmem(memcg);
> > mem_cgroup_free(memcg);
> > }
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index b512dd5e3a1c..d950cead66ca 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -185,6 +185,132 @@ static LIST_HEAD(shrinker_list);
> > static DECLARE_RWSEM(shrinker_rwsem);
> >
> > #ifdef CONFIG_MEMCG
> > +
> > +static int memcg_shrinker_map_size;
> > +static DEFINE_MUTEX(memcg_shrinker_map_mutex);
> > +
> > +static void free_shrinker_map_rcu(struct rcu_head *head)
> > +{
> > + kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > +}
> > +
> > +static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > + int size, int old_size)
> > +{
> > + struct memcg_shrinker_map *new, *old;
> > + int nid;
> > +
> > + lockdep_assert_held(&memcg_shrinker_map_mutex);
> > +
> > + for_each_node(nid) {
> > + old = rcu_dereference_protected(
> > + mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
> > + /* Not yet online memcg */
> > + if (!old)
> > + return 0;
> > +
> > + new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
> > + if (!new)
> > + return -ENOMEM;
> > +
> > + /* Set all old bits, clear all new bits */
> > + memset(new->map, (int)0xff, old_size);
> > + memset((void *)new->map + old_size, 0, size - old_size);
> > +
> > + rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > + call_rcu(&old->rcu, free_shrinker_map_rcu);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +void free_shrinker_maps(struct mem_cgroup *memcg)
> > +{
> > + struct mem_cgroup_per_node *pn;
> > + struct memcg_shrinker_map *map;
> > + int nid;
> > +
> > + if (mem_cgroup_is_root(memcg))
> > + return;
> > +
> > + for_each_node(nid) {
> > + pn = mem_cgroup_nodeinfo(memcg, nid);
> > + map = rcu_dereference_protected(pn->shrinker_map, true);
> > + if (map)
> > + kvfree(map);
>
> We should to forget about below patch and kill "if (map)" check here:
>
> https://lore.kernel.org/linux-mm/1611216029-34397-1-git-send-email-abaci-bugfix@linux.alibaba.com/
Aha, thanks for reminding me. I didn't notice that patch. It seems it
has been in the -mm tree. Will rebase on top of that patch.
>
> > + rcu_assign_pointer(pn->shrinker_map, NULL);
> > + }
> > +}
> > +
> > +int alloc_shrinker_maps(struct mem_cgroup *memcg)
> > +{
> > + struct memcg_shrinker_map *map;
> > + int nid, size, ret = 0;
> > +
> > + if (mem_cgroup_is_root(memcg))
> > + return 0;
> > +
> > + mutex_lock(&memcg_shrinker_map_mutex);
> > + size = memcg_shrinker_map_size;
> > + for_each_node(nid) {
> > + map = kvzalloc_node(sizeof(*map) + size, GFP_KERNEL, nid);
> > + if (!map) {
> > + free_shrinker_maps(memcg);
> > + ret = -ENOMEM;
> > + break;
> > + }
> > + rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, map);
> > + }
> > + mutex_unlock(&memcg_shrinker_map_mutex);
> > +
> > + return ret;
> > +}
> > +
> > +static int expand_shrinker_maps(int new_id)
> > +{
> > + int size, old_size, ret = 0;
> > + struct mem_cgroup *memcg;
> > +
> > + size = DIV_ROUND_UP(new_id + 1, BITS_PER_LONG) * sizeof(unsigned long);
> > + old_size = memcg_shrinker_map_size;
> > + if (size <= old_size)
> > + return 0;
> > +
> > + mutex_lock(&memcg_shrinker_map_mutex);
> > + if (!root_mem_cgroup)
> > + goto unlock;
> > +
> > + memcg = mem_cgroup_iter(NULL, NULL, NULL);
> > + do {
> > + if (mem_cgroup_is_root(memcg))
> > + continue;
> > + ret = expand_one_shrinker_map(memcg, size, old_size);
> > + if (ret) {
> > + mem_cgroup_iter_break(NULL, memcg);
> > + goto unlock;
> > + }
> > + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
> > +unlock:
> > + if (!ret)
> > + memcg_shrinker_map_size = size;
> > + mutex_unlock(&memcg_shrinker_map_mutex);
> > + return ret;
> > +}
> > +
> > +void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
> > +{
> > + if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
> > + struct memcg_shrinker_map *map;
> > +
> > + rcu_read_lock();
> > + map = rcu_dereference(memcg->nodeinfo[nid]->shrinker_map);
> > + /* Pairs with smp mb in shrink_slab() */
> > + smp_mb__before_atomic();
> > + set_bit(shrinker_id, map->map);
> > + rcu_read_unlock();
> > + }
> > +}
> > +
> > /*
> > * We allow subsystems to populate their shrinker-related
> > * LRU lists before register_shrinker_prepared() is called
> > @@ -212,7 +338,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> > goto unlock;
> >
> > if (id >= shrinker_nr_max) {
> > - if (memcg_expand_shrinker_maps(id)) {
> > + if (expand_shrinker_maps(id)) {
> > idr_remove(&shrinker_idr, id);
> > goto unlock;
> > }
> > @@ -601,7 +727,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
> > if (ret == SHRINK_EMPTY)
> > ret = 0;
> > else
> > - memcg_set_shrinker_bit(memcg, nid, i);
> > + set_shrinker_bit(memcg, nid, i);
> > }
> > freed += ret;
> >
> >
>
>
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