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revert "memcg: enhance memcg iterator to support predicates"
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Revert commit de57780 ("memcg: enhance memcg iterator to support
predicates")

I merged this prematurely - Michal and Johannes still disagree about the
overall design direction and the future remains unclear.

Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Andrew Morton authored and Linus Torvalds committed Sep 25, 2013
1 parent 30361e5 commit 694fbc0
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Showing 3 changed files with 32 additions and 103 deletions.
49 changes: 6 additions & 43 deletions include/linux/memcontrol.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,23 +53,6 @@ struct mem_cgroup_reclaim_cookie {
unsigned int generation;
};

enum mem_cgroup_filter_t {
VISIT, /* visit current node */
SKIP, /* skip the current node and continue traversal */
SKIP_TREE, /* skip the whole subtree and continue traversal */
};

/*
* mem_cgroup_filter_t predicate might instruct mem_cgroup_iter_cond how to
* iterate through the hierarchy tree. Each tree element is checked by the
* predicate before it is returned by the iterator. If a filter returns
* SKIP or SKIP_TREE then the iterator code continues traversal (with the
* next node down the hierarchy or the next node that doesn't belong under the
* memcg's subtree).
*/
typedef enum mem_cgroup_filter_t
(*mem_cgroup_iter_filter)(struct mem_cgroup *memcg, struct mem_cgroup *root);

#ifdef CONFIG_MEMCG
/*
* All "charge" functions with gfp_mask should use GFP_KERNEL or
Expand Down Expand Up @@ -137,18 +120,9 @@ mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
extern void mem_cgroup_end_migration(struct mem_cgroup *memcg,
struct page *oldpage, struct page *newpage, bool migration_ok);

struct mem_cgroup *mem_cgroup_iter_cond(struct mem_cgroup *root,
struct mem_cgroup *prev,
struct mem_cgroup_reclaim_cookie *reclaim,
mem_cgroup_iter_filter cond);

static inline struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
struct mem_cgroup *prev,
struct mem_cgroup_reclaim_cookie *reclaim)
{
return mem_cgroup_iter_cond(root, prev, reclaim, NULL);
}

struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *,
struct mem_cgroup *,
struct mem_cgroup_reclaim_cookie *);
void mem_cgroup_iter_break(struct mem_cgroup *, struct mem_cgroup *);

/*
Expand Down Expand Up @@ -260,8 +234,7 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
mem_cgroup_update_page_stat(page, idx, -1);
}

enum mem_cgroup_filter_t
mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
struct mem_cgroup *root);

void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
Expand Down Expand Up @@ -376,15 +349,6 @@ static inline void mem_cgroup_end_migration(struct mem_cgroup *memcg,
struct page *oldpage, struct page *newpage, bool migration_ok)
{
}
static inline struct mem_cgroup *
mem_cgroup_iter_cond(struct mem_cgroup *root,
struct mem_cgroup *prev,
struct mem_cgroup_reclaim_cookie *reclaim,
mem_cgroup_iter_filter cond)
{
/* first call must return non-NULL, second return NULL */
return (struct mem_cgroup *)(unsigned long)!prev;
}

static inline struct mem_cgroup *
mem_cgroup_iter(struct mem_cgroup *root,
Expand Down Expand Up @@ -471,11 +435,10 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
}

static inline
enum mem_cgroup_filter_t
mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
struct mem_cgroup *root)
{
return VISIT;
return false;
}

static inline void mem_cgroup_split_huge_fixup(struct page *head)
Expand Down
70 changes: 15 additions & 55 deletions mm/memcontrol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -862,23 +862,14 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
return memcg;
}

static enum mem_cgroup_filter_t
mem_cgroup_filter(struct mem_cgroup *memcg, struct mem_cgroup *root,
mem_cgroup_iter_filter cond)
{
if (!cond)
return VISIT;
return cond(memcg, root);
}

/*
* Returns a next (in a pre-order walk) alive memcg (with elevated css
* ref. count) or NULL if the whole root's subtree has been visited.
*
* helper function to be used by mem_cgroup_iter
*/
static struct mem_cgroup *__mem_cgroup_iter_next(struct mem_cgroup *root,
struct mem_cgroup *last_visited, mem_cgroup_iter_filter cond)
struct mem_cgroup *last_visited)
{
struct cgroup_subsys_state *prev_css, *next_css;

Expand All @@ -896,31 +887,11 @@ static struct mem_cgroup *__mem_cgroup_iter_next(struct mem_cgroup *root,
if (next_css) {
struct mem_cgroup *mem = mem_cgroup_from_css(next_css);

switch (mem_cgroup_filter(mem, root, cond)) {
case SKIP:
if (css_tryget(&mem->css))
return mem;
else {
prev_css = next_css;
goto skip_node;
case SKIP_TREE:
if (mem == root)
return NULL;
/*
* css_rightmost_descendant is not an optimal way to
* skip through a subtree (especially for imbalanced
* trees leaning to right) but that's what we have right
* now. More effective solution would be traversing
* right-up for first non-NULL without calling
* css_next_descendant_pre afterwards.
*/
prev_css = css_rightmost_descendant(next_css);
goto skip_node;
case VISIT:
if (css_tryget(&mem->css))
return mem;
else {
prev_css = next_css;
goto skip_node;
}
break;
}
}

Expand Down Expand Up @@ -984,7 +955,6 @@ static void mem_cgroup_iter_update(struct mem_cgroup_reclaim_iter *iter,
* @root: hierarchy root
* @prev: previously returned memcg, NULL on first invocation
* @reclaim: cookie for shared reclaim walks, NULL for full walks
* @cond: filter for visited nodes, NULL for no filter
*
* Returns references to children of the hierarchy below @root, or
* @root itself, or %NULL after a full round-trip.
Expand All @@ -997,18 +967,15 @@ static void mem_cgroup_iter_update(struct mem_cgroup_reclaim_iter *iter,
* divide up the memcgs in the hierarchy among all concurrent
* reclaimers operating on the same zone and priority.
*/
struct mem_cgroup *mem_cgroup_iter_cond(struct mem_cgroup *root,
struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
struct mem_cgroup *prev,
struct mem_cgroup_reclaim_cookie *reclaim,
mem_cgroup_iter_filter cond)
struct mem_cgroup_reclaim_cookie *reclaim)
{
struct mem_cgroup *memcg = NULL;
struct mem_cgroup *last_visited = NULL;

if (mem_cgroup_disabled()) {
/* first call must return non-NULL, second return NULL */
return (struct mem_cgroup *)(unsigned long)!prev;
}
if (mem_cgroup_disabled())
return NULL;

if (!root)
root = root_mem_cgroup;
Expand All @@ -1019,9 +986,7 @@ struct mem_cgroup *mem_cgroup_iter_cond(struct mem_cgroup *root,
if (!root->use_hierarchy && root != root_mem_cgroup) {
if (prev)
goto out_css_put;
if (mem_cgroup_filter(root, root, cond) == VISIT)
return root;
return NULL;
return root;
}

rcu_read_lock();
Expand All @@ -1044,7 +1009,7 @@ struct mem_cgroup *mem_cgroup_iter_cond(struct mem_cgroup *root,
last_visited = mem_cgroup_iter_load(iter, root, &seq);
}

memcg = __mem_cgroup_iter_next(root, last_visited, cond);
memcg = __mem_cgroup_iter_next(root, last_visited);

if (reclaim) {
mem_cgroup_iter_update(iter, last_visited, memcg, seq);
Expand All @@ -1055,11 +1020,7 @@ struct mem_cgroup *mem_cgroup_iter_cond(struct mem_cgroup *root,
reclaim->generation = iter->generation;
}

/*
* We have finished the whole tree walk or no group has been
* visited because filter told us to skip the root node.
*/
if (!memcg && (prev || (cond && !last_visited)))
if (prev && !memcg)
goto out_unlock;
}
out_unlock:
Expand Down Expand Up @@ -1804,27 +1765,26 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
* a) it is over its soft limit
* b) any parent up the hierarchy is over its soft limit
*/
enum mem_cgroup_filter_t
mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
struct mem_cgroup *root)
{
struct mem_cgroup *parent = memcg;

if (res_counter_soft_limit_excess(&memcg->res))
return VISIT;
return true;

/*
* If any parent up to the root in the hierarchy is over its soft limit
* then we have to obey and reclaim from this group as well.
*/
while ((parent = parent_mem_cgroup(parent))) {
if (res_counter_soft_limit_excess(&parent->res))
return VISIT;
return true;
if (parent == root)
break;
}

return SKIP;
return false;
}

static DEFINE_SPINLOCK(memcg_oom_lock);
Expand Down
16 changes: 11 additions & 5 deletions mm/vmscan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2185,16 +2185,21 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
.zone = zone,
.priority = sc->priority,
};
struct mem_cgroup *memcg = NULL;
mem_cgroup_iter_filter filter = (soft_reclaim) ?
mem_cgroup_soft_reclaim_eligible : NULL;
struct mem_cgroup *memcg;

nr_reclaimed = sc->nr_reclaimed;
nr_scanned = sc->nr_scanned;

while ((memcg = mem_cgroup_iter_cond(root, memcg, &reclaim, filter))) {
memcg = mem_cgroup_iter(root, NULL, &reclaim);
do {
struct lruvec *lruvec;

if (soft_reclaim &&
!mem_cgroup_soft_reclaim_eligible(memcg, root)) {
memcg = mem_cgroup_iter(root, memcg, &reclaim);
continue;
}

lruvec = mem_cgroup_zone_lruvec(zone, memcg);

shrink_lruvec(lruvec, sc);
Expand All @@ -2214,7 +2219,8 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
mem_cgroup_iter_break(root, memcg);
break;
}
}
memcg = mem_cgroup_iter(root, memcg, &reclaim);
} while (memcg);

vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
sc->nr_scanned - nr_scanned,
Expand Down

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