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revert "memcg, vmscan: integrate soft reclaim tighter with zone shrin…
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…king code"

Revert commit 3b38722 ("memcg, vmscan: integrate soft reclaim
tighter with zone shrinking code")

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 bb4cc1a commit 0608f43
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Showing 3 changed files with 175 additions and 60 deletions.
10 changes: 7 additions & 3 deletions include/linux/memcontrol.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -234,7 +234,9 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
mem_cgroup_update_page_stat(page, idx, -1);
}

bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg);
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask,
unsigned long *total_scanned);

void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
Expand Down Expand Up @@ -434,9 +436,11 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
}

static inline
bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg)
unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask,
unsigned long *total_scanned)
{
return false;
return 0;
}

static inline void mem_cgroup_split_huge_fixup(struct page *head)
Expand Down
163 changes: 142 additions & 21 deletions mm/memcontrol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1991,28 +1991,57 @@ static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
}
#endif

/*
* A group is eligible for the soft limit reclaim if
* a) it is over its soft limit
* b) any parent up the hierarchy is over its soft limit
*/
bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg)
{
struct mem_cgroup *parent = memcg;

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

/*
* If any parent up 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 true;
static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
struct zone *zone,
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 = {
.zone = zone,
.priority = 0,
};

excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;

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;
}
if (!mem_cgroup_reclaimable(victim, false))
continue;
total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
zone, &nr_scanned);
*total_scanned += nr_scanned;
if (!res_counter_soft_limit_excess(&root_memcg->res))
break;
}

return false;
mem_cgroup_iter_break(root_memcg, victim);
return total;
}

static DEFINE_SPINLOCK(memcg_oom_lock);
Expand Down Expand Up @@ -4761,6 +4790,98 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
return ret;
}

unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask,
unsigned long *total_scanned)
{
unsigned long nr_reclaimed = 0;
struct mem_cgroup_per_zone *mz, *next_mz = NULL;
unsigned long reclaimed;
int loop = 0;
struct mem_cgroup_tree_per_zone *mctz;
unsigned long long excess;
unsigned long nr_scanned;

if (order > 0)
return 0;

mctz = soft_limit_tree_node_zone(zone_to_nid(zone), zone_idx(zone));
/*
* 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;

nr_scanned = 0;
reclaimed = mem_cgroup_soft_reclaim(mz->memcg, zone,
gfp_mask, &nr_scanned);
nr_reclaimed += reclaimed;
*total_scanned += nr_scanned;
spin_lock(&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) {
do {
/*
* Loop until we find yet another one.
*
* By the time we get the soft_limit lock
* again, someone might have aded the
* group back on the RB tree. Iterate to
* make sure we get a different mem.
* mem_cgroup_largest_soft_limit_node returns
* NULL if no other cgroup is present on
* the tree
*/
next_mz =
__mem_cgroup_largest_soft_limit_node(mctz);
if (next_mz == mz)
css_put(&next_mz->memcg->css);
else /* next_mz == NULL or other memcg */
break;
} while (1);
}
__mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
excess = res_counter_soft_limit_excess(&mz->memcg->res);
/*
* 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->memcg, mz, mctz, excess);
spin_unlock(&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;
}

/**
* mem_cgroup_force_empty_list - clears LRU of a group
* @memcg: group to clear
Expand Down
62 changes: 26 additions & 36 deletions mm/vmscan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -139,21 +139,11 @@ static bool global_reclaim(struct scan_control *sc)
{
return !sc->target_mem_cgroup;
}

static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc)
{
return !mem_cgroup_disabled() && global_reclaim(sc);
}
#else
static bool global_reclaim(struct scan_control *sc)
{
return true;
}

static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc)
{
return false;
}
#endif

unsigned long zone_reclaimable_pages(struct zone *zone)
Expand Down Expand Up @@ -2174,8 +2164,7 @@ static inline bool should_continue_reclaim(struct zone *zone,
}
}

static void
__shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
static void shrink_zone(struct zone *zone, struct scan_control *sc)
{
unsigned long nr_reclaimed, nr_scanned;

Expand All @@ -2194,12 +2183,6 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
do {
struct lruvec *lruvec;

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

lruvec = mem_cgroup_zone_lruvec(zone, memcg);

shrink_lruvec(lruvec, sc);
Expand Down Expand Up @@ -2230,24 +2213,6 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
sc->nr_scanned - nr_scanned, sc));
}


static void shrink_zone(struct zone *zone, struct scan_control *sc)
{
bool do_soft_reclaim = mem_cgroup_should_soft_reclaim(sc);
unsigned long nr_scanned = sc->nr_scanned;

__shrink_zone(zone, sc, do_soft_reclaim);

/*
* No group is over the soft limit or those that are do not have
* pages in the zone we are reclaiming so we have to reclaim everybody
*/
if (do_soft_reclaim && (sc->nr_scanned == nr_scanned)) {
__shrink_zone(zone, sc, false);
return;
}
}

/* Returns true if compaction should go ahead for a high-order request */
static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
{
Expand Down Expand Up @@ -2309,6 +2274,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
{
struct zoneref *z;
struct zone *zone;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
bool aborted_reclaim = false;

/*
Expand Down Expand Up @@ -2348,6 +2315,18 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
continue;
}
}
/*
* This steals pages from memory cgroups over softlimit
* and returns the number of reclaimed pages and
* scanned pages. This works for global memory pressure
* and balancing, not for a memcg's limit.
*/
nr_soft_scanned = 0;
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
sc->order, sc->gfp_mask,
&nr_soft_scanned);
sc->nr_reclaimed += nr_soft_reclaimed;
sc->nr_scanned += nr_soft_scanned;
/* need some check for avoid more shrink_zone() */
}

Expand Down Expand Up @@ -2941,6 +2920,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
{
int i;
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.priority = DEF_PRIORITY,
Expand Down Expand Up @@ -3055,6 +3036,15 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,

sc.nr_scanned = 0;

nr_soft_scanned = 0;
/*
* Call soft limit reclaim before calling shrink_zone.
*/
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
order, sc.gfp_mask,
&nr_soft_scanned);
sc.nr_reclaimed += nr_soft_reclaimed;

/*
* There should be no need to raise the scanning
* priority if enough pages are already being scanned
Expand Down

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