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Date: Tue, 25 Jun 2024 09:06:41 +0200
From: Michal Hocko <mhocko@...e.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
Shakeel Butt <shakeel.butt@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 02/14] mm: memcg: move soft limit reclaim code to
memcontrol-v1.c
On Mon 24-06-24 17:58:54, Roman Gushchin wrote:
> Soft limits are cgroup v1-specific and are not supported by cgroup v2,
> so let's move the corresponding code into memcontrol-v1.c.
>
> Aside from simple moving the code, this commits introduces a trivial
> memcg1_soft_limit_reset() function to reset soft limits and also
> moves the global soft limit tree initialization code into a new
> memcg1_init() function.
>
> It also moves corresponding declarations shared between memcontrol.c
> and memcontrol-v1.c into mm/memcontrol-v1.h.
>
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
I haven't done line for line check here and in other patches that move a
lot of code. I like you have separated the renaming into its own patch
because this makes review just easier.
Acked-by: Michal Hocko <mhocko@...e.com>
> ---
> mm/memcontrol-v1.c | 342 +++++++++++++++++++++++++++++++++++++++++++++
> mm/memcontrol-v1.h | 7 +
> mm/memcontrol.c | 337 +-------------------------------------------
> 3 files changed, 353 insertions(+), 333 deletions(-)
>
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index a941446ba575..2ccb8406fa84 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -1,3 +1,345 @@
> // SPDX-License-Identifier: GPL-2.0-or-later
>
> +#include <linux/memcontrol.h>
> +#include <linux/swap.h>
> +#include <linux/mm_inline.h>
> +
> #include "memcontrol-v1.h"
> +
> +/*
> + * Cgroups above their limits are maintained in a RB-Tree, independent of
> + * their hierarchy representation
> + */
> +
> +struct mem_cgroup_tree_per_node {
> + struct rb_root rb_root;
> + struct rb_node *rb_rightmost;
> + spinlock_t lock;
> +};
> +
> +struct mem_cgroup_tree {
> + struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
> +};
> +
> +static struct mem_cgroup_tree soft_limit_tree __read_mostly;
> +
> +/*
> + * Maximum loops in mem_cgroup_soft_reclaim(), used for soft
> + * limit reclaim to prevent infinite loops, if they ever occur.
> + */
> +#define MEM_CGROUP_MAX_RECLAIM_LOOPS 100
> +#define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2
> +
> +static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
> + struct mem_cgroup_tree_per_node *mctz,
> + unsigned long new_usage_in_excess)
> +{
> + struct rb_node **p = &mctz->rb_root.rb_node;
> + struct rb_node *parent = NULL;
> + struct mem_cgroup_per_node *mz_node;
> + bool rightmost = true;
> +
> + if (mz->on_tree)
> + return;
> +
> + mz->usage_in_excess = new_usage_in_excess;
> + if (!mz->usage_in_excess)
> + return;
> + while (*p) {
> + parent = *p;
> + mz_node = rb_entry(parent, struct mem_cgroup_per_node,
> + tree_node);
> + if (mz->usage_in_excess < mz_node->usage_in_excess) {
> + p = &(*p)->rb_left;
> + rightmost = false;
> + } else {
> + p = &(*p)->rb_right;
> + }
> + }
> +
> + if (rightmost)
> + mctz->rb_rightmost = &mz->tree_node;
> +
> + rb_link_node(&mz->tree_node, parent, p);
> + rb_insert_color(&mz->tree_node, &mctz->rb_root);
> + mz->on_tree = true;
> +}
> +
> +static void __mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
> + struct mem_cgroup_tree_per_node *mctz)
> +{
> + if (!mz->on_tree)
> + return;
> +
> + if (&mz->tree_node == mctz->rb_rightmost)
> + mctz->rb_rightmost = rb_prev(&mz->tree_node);
> +
> + rb_erase(&mz->tree_node, &mctz->rb_root);
> + mz->on_tree = false;
> +}
> +
> +static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
> + struct mem_cgroup_tree_per_node *mctz)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&mctz->lock, flags);
> + __mem_cgroup_remove_exceeded(mz, mctz);
> + spin_unlock_irqrestore(&mctz->lock, flags);
> +}
> +
> +static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
> +{
> + unsigned long nr_pages = page_counter_read(&memcg->memory);
> + unsigned long soft_limit = READ_ONCE(memcg->soft_limit);
> + unsigned long excess = 0;
> +
> + if (nr_pages > soft_limit)
> + excess = nr_pages - soft_limit;
> +
> + return excess;
> +}
> +
> +void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
> +{
> + unsigned long excess;
> + struct mem_cgroup_per_node *mz;
> + struct mem_cgroup_tree_per_node *mctz;
> +
> + if (lru_gen_enabled()) {
> + if (soft_limit_excess(memcg))
> + lru_gen_soft_reclaim(memcg, nid);
> + return;
> + }
> +
> + mctz = soft_limit_tree.rb_tree_per_node[nid];
> + if (!mctz)
> + return;
> + /*
> + * Necessary to update all ancestors when hierarchy is used.
> + * because their event counter is not touched.
> + */
> + for (; memcg; memcg = parent_mem_cgroup(memcg)) {
> + mz = memcg->nodeinfo[nid];
> + excess = soft_limit_excess(memcg);
> + /*
> + * We have to update the tree if mz is on RB-tree or
> + * mem is over its softlimit.
> + */
> + if (excess || mz->on_tree) {
> + unsigned long flags;
> +
> + spin_lock_irqsave(&mctz->lock, flags);
> + /* if on-tree, remove it */
> + if (mz->on_tree)
> + __mem_cgroup_remove_exceeded(mz, mctz);
> + /*
> + * Insert again. mz->usage_in_excess will be updated.
> + * If excess is 0, no tree ops.
> + */
> + __mem_cgroup_insert_exceeded(mz, mctz, excess);
> + spin_unlock_irqrestore(&mctz->lock, flags);
> + }
> + }
> +}
> +
> +void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
> +{
> + struct mem_cgroup_tree_per_node *mctz;
> + struct mem_cgroup_per_node *mz;
> + int nid;
> +
> + for_each_node(nid) {
> + mz = memcg->nodeinfo[nid];
> + mctz = soft_limit_tree.rb_tree_per_node[nid];
> + if (mctz)
> + mem_cgroup_remove_exceeded(mz, mctz);
> + }
> +}
> +
> +static struct mem_cgroup_per_node *
> +__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
> +{
> + struct mem_cgroup_per_node *mz;
> +
> +retry:
> + mz = NULL;
> + if (!mctz->rb_rightmost)
> + goto done; /* Nothing to reclaim from */
> +
> + mz = rb_entry(mctz->rb_rightmost,
> + struct mem_cgroup_per_node, tree_node);
> + /*
> + * Remove the node now but someone else can add it back,
> + * we will to add it back at the end of reclaim to its correct
> + * position in the tree.
> + */
> + __mem_cgroup_remove_exceeded(mz, mctz);
> + if (!soft_limit_excess(mz->memcg) ||
> + !css_tryget(&mz->memcg->css))
> + goto retry;
> +done:
> + return mz;
> +}
> +
> +static struct mem_cgroup_per_node *
> +mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
> +{
> + struct mem_cgroup_per_node *mz;
> +
> + spin_lock_irq(&mctz->lock);
> + mz = __mem_cgroup_largest_soft_limit_node(mctz);
> + spin_unlock_irq(&mctz->lock);
> + return mz;
> +}
> +
> +static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
> + pg_data_t *pgdat,
> + gfp_t gfp_mask,
> + unsigned long *total_scanned)
> +{
> + struct mem_cgroup *victim = NULL;
> + int total = 0;
> + int loop = 0;
> + unsigned long excess;
> + unsigned long nr_scanned;
> + struct mem_cgroup_reclaim_cookie reclaim = {
> + .pgdat = pgdat,
> + };
> +
> + excess = soft_limit_excess(root_memcg);
> +
> + while (1) {
> + victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
> + if (!victim) {
> + loop++;
> + if (loop >= 2) {
> + /*
> + * If we have not been able to reclaim
> + * anything, it might because there are
> + * no reclaimable pages under this hierarchy
> + */
> + if (!total)
> + break;
> + /*
> + * We want to do more targeted reclaim.
> + * excess >> 2 is not to excessive so as to
> + * reclaim too much, nor too less that we keep
> + * coming back to reclaim from this cgroup
> + */
> + if (total >= (excess >> 2) ||
> + (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
> + break;
> + }
> + continue;
> + }
> + total += mem_cgroup_shrink_node(victim, gfp_mask, false,
> + pgdat, &nr_scanned);
> + *total_scanned += nr_scanned;
> + if (!soft_limit_excess(root_memcg))
> + break;
> + }
> + mem_cgroup_iter_break(root_memcg, victim);
> + return total;
> +}
> +
> +unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
> + gfp_t gfp_mask,
> + unsigned long *total_scanned)
> +{
> + unsigned long nr_reclaimed = 0;
> + struct mem_cgroup_per_node *mz, *next_mz = NULL;
> + unsigned long reclaimed;
> + int loop = 0;
> + struct mem_cgroup_tree_per_node *mctz;
> + unsigned long excess;
> +
> + if (lru_gen_enabled())
> + return 0;
> +
> + if (order > 0)
> + return 0;
> +
> + mctz = soft_limit_tree.rb_tree_per_node[pgdat->node_id];
> +
> + /*
> + * Do not even bother to check the largest node if the root
> + * is empty. Do it lockless to prevent lock bouncing. Races
> + * are acceptable as soft limit is best effort anyway.
> + */
> + if (!mctz || RB_EMPTY_ROOT(&mctz->rb_root))
> + return 0;
> +
> + /*
> + * This loop can run a while, specially if mem_cgroup's continuously
> + * keep exceeding their soft limit and putting the system under
> + * pressure
> + */
> + do {
> + if (next_mz)
> + mz = next_mz;
> + else
> + mz = mem_cgroup_largest_soft_limit_node(mctz);
> + if (!mz)
> + break;
> +
> + reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat,
> + gfp_mask, total_scanned);
> + nr_reclaimed += reclaimed;
> + spin_lock_irq(&mctz->lock);
> +
> + /*
> + * If we failed to reclaim anything from this memory cgroup
> + * it is time to move on to the next cgroup
> + */
> + next_mz = NULL;
> + if (!reclaimed)
> + next_mz = __mem_cgroup_largest_soft_limit_node(mctz);
> +
> + excess = soft_limit_excess(mz->memcg);
> + /*
> + * One school of thought says that we should not add
> + * back the node to the tree if reclaim returns 0.
> + * But our reclaim could return 0, simply because due
> + * to priority we are exposing a smaller subset of
> + * memory to reclaim from. Consider this as a longer
> + * term TODO.
> + */
> + /* If excess == 0, no tree ops */
> + __mem_cgroup_insert_exceeded(mz, mctz, excess);
> + spin_unlock_irq(&mctz->lock);
> + css_put(&mz->memcg->css);
> + loop++;
> + /*
> + * Could not reclaim anything and there are no more
> + * mem cgroups to try or we seem to be looping without
> + * reclaiming anything.
> + */
> + if (!nr_reclaimed &&
> + (next_mz == NULL ||
> + loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
> + break;
> + } while (!nr_reclaimed);
> + if (next_mz)
> + css_put(&next_mz->memcg->css);
> + return nr_reclaimed;
> +}
> +
> +static int __init memcg1_init(void)
> +{
> + int node;
> +
> + for_each_node(node) {
> + struct mem_cgroup_tree_per_node *rtpn;
> +
> + rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node);
> +
> + rtpn->rb_root = RB_ROOT;
> + rtpn->rb_rightmost = NULL;
> + spin_lock_init(&rtpn->lock);
> + soft_limit_tree.rb_tree_per_node[node] = rtpn;
> + }
> +
> + return 0;
> +}
> +subsys_initcall(memcg1_init);
> diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
> index 7c5f094755ff..4da6fa561c6d 100644
> --- a/mm/memcontrol-v1.h
> +++ b/mm/memcontrol-v1.h
> @@ -3,5 +3,12 @@
> #ifndef __MM_MEMCONTROL_V1_H
> #define __MM_MEMCONTROL_V1_H
>
> +void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid);
> +void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg);
> +
> +static inline void memcg1_soft_limit_reset(struct mem_cgroup *memcg)
> +{
> + WRITE_ONCE(memcg->soft_limit, PAGE_COUNTER_MAX);
> +}
>
> #endif /* __MM_MEMCONTROL_V1_H */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 974bd160838c..003e944f34ea 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -72,6 +72,7 @@
> #include <net/ip.h>
> #include "slab.h"
> #include "swap.h"
> +#include "memcontrol-v1.h"
>
> #include <linux/uaccess.h>
>
> @@ -108,23 +109,6 @@ static bool do_memsw_account(void)
> #define THRESHOLDS_EVENTS_TARGET 128
> #define SOFTLIMIT_EVENTS_TARGET 1024
>
> -/*
> - * Cgroups above their limits are maintained in a RB-Tree, independent of
> - * their hierarchy representation
> - */
> -
> -struct mem_cgroup_tree_per_node {
> - struct rb_root rb_root;
> - struct rb_node *rb_rightmost;
> - spinlock_t lock;
> -};
> -
> -struct mem_cgroup_tree {
> - struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
> -};
> -
> -static struct mem_cgroup_tree soft_limit_tree __read_mostly;
> -
> /* for OOM */
> struct mem_cgroup_eventfd_list {
> struct list_head list;
> @@ -199,13 +183,6 @@ static struct move_charge_struct {
> .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
> };
>
> -/*
> - * Maximum loops in mem_cgroup_soft_reclaim(), used for soft
> - * limit reclaim to prevent infinite loops, if they ever occur.
> - */
> -#define MEM_CGROUP_MAX_RECLAIM_LOOPS 100
> -#define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2
> -
> /* for encoding cft->private value on file */
> enum res_type {
> _MEM,
> @@ -413,169 +390,6 @@ ino_t page_cgroup_ino(struct page *page)
> return ino;
> }
>
> -static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
> - struct mem_cgroup_tree_per_node *mctz,
> - unsigned long new_usage_in_excess)
> -{
> - struct rb_node **p = &mctz->rb_root.rb_node;
> - struct rb_node *parent = NULL;
> - struct mem_cgroup_per_node *mz_node;
> - bool rightmost = true;
> -
> - if (mz->on_tree)
> - return;
> -
> - mz->usage_in_excess = new_usage_in_excess;
> - if (!mz->usage_in_excess)
> - return;
> - while (*p) {
> - parent = *p;
> - mz_node = rb_entry(parent, struct mem_cgroup_per_node,
> - tree_node);
> - if (mz->usage_in_excess < mz_node->usage_in_excess) {
> - p = &(*p)->rb_left;
> - rightmost = false;
> - } else {
> - p = &(*p)->rb_right;
> - }
> - }
> -
> - if (rightmost)
> - mctz->rb_rightmost = &mz->tree_node;
> -
> - rb_link_node(&mz->tree_node, parent, p);
> - rb_insert_color(&mz->tree_node, &mctz->rb_root);
> - mz->on_tree = true;
> -}
> -
> -static void __mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
> - struct mem_cgroup_tree_per_node *mctz)
> -{
> - if (!mz->on_tree)
> - return;
> -
> - if (&mz->tree_node == mctz->rb_rightmost)
> - mctz->rb_rightmost = rb_prev(&mz->tree_node);
> -
> - rb_erase(&mz->tree_node, &mctz->rb_root);
> - mz->on_tree = false;
> -}
> -
> -static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
> - struct mem_cgroup_tree_per_node *mctz)
> -{
> - unsigned long flags;
> -
> - spin_lock_irqsave(&mctz->lock, flags);
> - __mem_cgroup_remove_exceeded(mz, mctz);
> - spin_unlock_irqrestore(&mctz->lock, flags);
> -}
> -
> -static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
> -{
> - unsigned long nr_pages = page_counter_read(&memcg->memory);
> - unsigned long soft_limit = READ_ONCE(memcg->soft_limit);
> - unsigned long excess = 0;
> -
> - if (nr_pages > soft_limit)
> - excess = nr_pages - soft_limit;
> -
> - return excess;
> -}
> -
> -static void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
> -{
> - unsigned long excess;
> - struct mem_cgroup_per_node *mz;
> - struct mem_cgroup_tree_per_node *mctz;
> -
> - if (lru_gen_enabled()) {
> - if (soft_limit_excess(memcg))
> - lru_gen_soft_reclaim(memcg, nid);
> - return;
> - }
> -
> - mctz = soft_limit_tree.rb_tree_per_node[nid];
> - if (!mctz)
> - return;
> - /*
> - * Necessary to update all ancestors when hierarchy is used.
> - * because their event counter is not touched.
> - */
> - for (; memcg; memcg = parent_mem_cgroup(memcg)) {
> - mz = memcg->nodeinfo[nid];
> - excess = soft_limit_excess(memcg);
> - /*
> - * We have to update the tree if mz is on RB-tree or
> - * mem is over its softlimit.
> - */
> - if (excess || mz->on_tree) {
> - unsigned long flags;
> -
> - spin_lock_irqsave(&mctz->lock, flags);
> - /* if on-tree, remove it */
> - if (mz->on_tree)
> - __mem_cgroup_remove_exceeded(mz, mctz);
> - /*
> - * Insert again. mz->usage_in_excess will be updated.
> - * If excess is 0, no tree ops.
> - */
> - __mem_cgroup_insert_exceeded(mz, mctz, excess);
> - spin_unlock_irqrestore(&mctz->lock, flags);
> - }
> - }
> -}
> -
> -static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
> -{
> - struct mem_cgroup_tree_per_node *mctz;
> - struct mem_cgroup_per_node *mz;
> - int nid;
> -
> - for_each_node(nid) {
> - mz = memcg->nodeinfo[nid];
> - mctz = soft_limit_tree.rb_tree_per_node[nid];
> - if (mctz)
> - mem_cgroup_remove_exceeded(mz, mctz);
> - }
> -}
> -
> -static struct mem_cgroup_per_node *
> -__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
> -{
> - struct mem_cgroup_per_node *mz;
> -
> -retry:
> - mz = NULL;
> - if (!mctz->rb_rightmost)
> - goto done; /* Nothing to reclaim from */
> -
> - mz = rb_entry(mctz->rb_rightmost,
> - struct mem_cgroup_per_node, tree_node);
> - /*
> - * Remove the node now but someone else can add it back,
> - * we will to add it back at the end of reclaim to its correct
> - * position in the tree.
> - */
> - __mem_cgroup_remove_exceeded(mz, mctz);
> - if (!soft_limit_excess(mz->memcg) ||
> - !css_tryget(&mz->memcg->css))
> - goto retry;
> -done:
> - return mz;
> -}
> -
> -static struct mem_cgroup_per_node *
> -mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
> -{
> - struct mem_cgroup_per_node *mz;
> -
> - spin_lock_irq(&mctz->lock);
> - mz = __mem_cgroup_largest_soft_limit_node(mctz);
> - spin_unlock_irq(&mctz->lock);
> - return mz;
> -}
> -
> /* Subset of node_stat_item for memcg stats */
> static const unsigned int memcg_node_stat_items[] = {
> NR_INACTIVE_ANON,
> @@ -1980,56 +1794,6 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
> return ret;
> }
>
> -static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
> - pg_data_t *pgdat,
> - gfp_t gfp_mask,
> - unsigned long *total_scanned)
> -{
> - struct mem_cgroup *victim = NULL;
> - int total = 0;
> - int loop = 0;
> - unsigned long excess;
> - unsigned long nr_scanned;
> - struct mem_cgroup_reclaim_cookie reclaim = {
> - .pgdat = pgdat,
> - };
> -
> - excess = soft_limit_excess(root_memcg);
> -
> - while (1) {
> - victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
> - if (!victim) {
> - loop++;
> - if (loop >= 2) {
> - /*
> - * If we have not been able to reclaim
> - * anything, it might because there are
> - * no reclaimable pages under this hierarchy
> - */
> - if (!total)
> - break;
> - /*
> - * We want to do more targeted reclaim.
> - * excess >> 2 is not to excessive so as to
> - * reclaim too much, nor too less that we keep
> - * coming back to reclaim from this cgroup
> - */
> - if (total >= (excess >> 2) ||
> - (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
> - break;
> - }
> - continue;
> - }
> - total += mem_cgroup_shrink_node(victim, gfp_mask, false,
> - pgdat, &nr_scanned);
> - *total_scanned += nr_scanned;
> - if (!soft_limit_excess(root_memcg))
> - break;
> - }
> - mem_cgroup_iter_break(root_memcg, victim);
> - return total;
> -}
> -
> #ifdef CONFIG_LOCKDEP
> static struct lockdep_map memcg_oom_lock_dep_map = {
> .name = "memcg_oom_lock",
> @@ -3925,88 +3689,6 @@ static int mem_cgroup_resize_max(struct mem_cgroup *memcg,
> return ret;
> }
>
> -unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
> - gfp_t gfp_mask,
> - unsigned long *total_scanned)
> -{
> - unsigned long nr_reclaimed = 0;
> - struct mem_cgroup_per_node *mz, *next_mz = NULL;
> - unsigned long reclaimed;
> - int loop = 0;
> - struct mem_cgroup_tree_per_node *mctz;
> - unsigned long excess;
> -
> - if (lru_gen_enabled())
> - return 0;
> -
> - if (order > 0)
> - return 0;
> -
> - mctz = soft_limit_tree.rb_tree_per_node[pgdat->node_id];
> -
> - /*
> - * Do not even bother to check the largest node if the root
> - * is empty. Do it lockless to prevent lock bouncing. Races
> - * are acceptable as soft limit is best effort anyway.
> - */
> - if (!mctz || RB_EMPTY_ROOT(&mctz->rb_root))
> - return 0;
> -
> - /*
> - * This loop can run a while, specially if mem_cgroup's continuously
> - * keep exceeding their soft limit and putting the system under
> - * pressure
> - */
> - do {
> - if (next_mz)
> - mz = next_mz;
> - else
> - mz = mem_cgroup_largest_soft_limit_node(mctz);
> - if (!mz)
> - break;
> -
> - reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat,
> - gfp_mask, total_scanned);
> - nr_reclaimed += reclaimed;
> - spin_lock_irq(&mctz->lock);
> -
> - /*
> - * If we failed to reclaim anything from this memory cgroup
> - * it is time to move on to the next cgroup
> - */
> - next_mz = NULL;
> - if (!reclaimed)
> - next_mz = __mem_cgroup_largest_soft_limit_node(mctz);
> -
> - excess = soft_limit_excess(mz->memcg);
> - /*
> - * One school of thought says that we should not add
> - * back the node to the tree if reclaim returns 0.
> - * But our reclaim could return 0, simply because due
> - * to priority we are exposing a smaller subset of
> - * memory to reclaim from. Consider this as a longer
> - * term TODO.
> - */
> - /* If excess == 0, no tree ops */
> - __mem_cgroup_insert_exceeded(mz, mctz, excess);
> - spin_unlock_irq(&mctz->lock);
> - css_put(&mz->memcg->css);
> - loop++;
> - /*
> - * Could not reclaim anything and there are no more
> - * mem cgroups to try or we seem to be looping without
> - * reclaiming anything.
> - */
> - if (!nr_reclaimed &&
> - (next_mz == NULL ||
> - loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
> - break;
> - } while (!nr_reclaimed);
> - if (next_mz)
> - css_put(&next_mz->memcg->css);
> - return nr_reclaimed;
> -}
> -
> /*
> * Reclaims as many pages from the given memcg as possible.
> *
> @@ -5784,7 +5466,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
> return ERR_CAST(memcg);
>
> page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
> - WRITE_ONCE(memcg->soft_limit, PAGE_COUNTER_MAX);
> + memcg1_soft_limit_reset(memcg);
> #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
> memcg->zswap_max = PAGE_COUNTER_MAX;
> WRITE_ONCE(memcg->zswap_writeback,
> @@ -5957,7 +5639,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
> page_counter_set_min(&memcg->memory, 0);
> page_counter_set_low(&memcg->memory, 0);
> page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
> - WRITE_ONCE(memcg->soft_limit, PAGE_COUNTER_MAX);
> + memcg1_soft_limit_reset(memcg);
> page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
> memcg_wb_domain_size_changed(memcg);
> }
> @@ -7984,7 +7666,7 @@ __setup("cgroup.memory=", cgroup_memory);
> */
> static int __init mem_cgroup_init(void)
> {
> - int cpu, node;
> + int cpu;
>
> /*
> * Currently s32 type (can refer to struct batched_lruvec_stat) is
> @@ -8001,17 +7683,6 @@ static int __init mem_cgroup_init(void)
> INIT_WORK(&per_cpu_ptr(&memcg_stock, cpu)->work,
> drain_local_stock);
>
> - for_each_node(node) {
> - struct mem_cgroup_tree_per_node *rtpn;
> -
> - rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node);
> -
> - rtpn->rb_root = RB_ROOT;
> - rtpn->rb_rightmost = NULL;
> - spin_lock_init(&rtpn->lock);
> - soft_limit_tree.rb_tree_per_node[node] = rtpn;
> - }
> -
> return 0;
> }
> subsys_initcall(mem_cgroup_init);
> --
> 2.45.2
--
Michal Hocko
SUSE Labs
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