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Subject[PATCH v5 5/7] mm: rework reclaim_stat counters
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Currently there is two types of reclaim-stat counters:
recent_scanned (pages picked from from lru),
recent_rotated (pages putted back to active lru).
Reclaimer uses ratio recent_rotated / recent_scanned
for balancing pressure between file and anon pages.

But if we pick page from lru we can either reclaim it or put it back to lru, thus:
recent_scanned == recent_rotated[inactive] + recent_rotated[active] + reclaimed
This can be called "The Law of Conservation of Memory" =)

Thus recent_rotated counters for each lru list is enough, reclaimed pages can be
counted as rotatation into inactive lru. After that reclaimer can use this ratio:
recent_rotated[active] / (recent_rotated[active] + recent_rotated[inactive])

After this patch struct zone_reclaimer_stat has only one array: recent_rotated,
which is directly indexed by lru list index:

before patch:

LRU_ACTIVE_ANON -> LRU_ACTIVE_ANON : recent_scanned[ANON]++, recent_rotated[ANON]++
LRU_INACTIVE_ANON -> LRU_ACTIVE_ANON : recent_scanned[ANON]++, recent_rotated[ANON]++
LRU_ACTIVE_ANON -> LRU_INACTIVE_ANON : recent_scanned[ANON]++
LRU_INACTIVE_ANON -> LRU_INACTIVE_ANON : recent_scanned[ANON]++

after patch:

LRU_ACTIVE_ANON -> LRU_ACTIVE_ANON : recent_rotated[LRU_ACTIVE_ANON]++
LRU_INACTIVE_ANON -> LRU_ACTIVE_ANON : recent_rotated[LRU_ACTIVE_ANON]++
LRU_ACTIVE_ANON -> LRU_INACTIVE_ANON : recent_rotated[LRU_INACTIVE_ANON]++
LRU_INACTIVE_ANON -> LRU_INACTIVE_ANON : recent_rotated[LRU_INACTIVE_ANON]++

recent_scanned[ANON] === recent_rotated[LRU_ACTIVE_ANON] + recent_rotated[LRU_INACTIVE_ANON]
recent_rotated[ANON] === recent_rotated[LRU_ACTIVE_ANON]

(and the same for FILE/LRU_ACTIVE_FILE/LRU_INACTIVE_FILE)

v5:
* resolve conflict with "memcg: fix GPF when cgroup removal races with last exit"

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>

---
add/remove: 0/0 grow/shrink: 3/8 up/down: 32/-135 (-103)
function old new delta
shrink_mem_cgroup_zone 1507 1526 +19
free_area_init_node 852 862 +10
put_page_testzero 30 33 +3
mem_control_stat_show 754 750 -4
putback_inactive_pages 635 629 -6
lru_add_page_tail 364 349 -15
__pagevec_lru_add_fn 266 249 -17
lru_deactivate_fn 500 482 -18
__activate_page 365 347 -18
update_page_reclaim_stat 89 64 -25
static.shrink_active_list 853 821 -32
---
include/linux/mmzone.h | 11 +++++------
mm/memcontrol.c | 29 +++++++++++++++++------------
mm/page_alloc.c | 6 ++----
mm/swap.c | 29 ++++++++++-------------------
mm/vmscan.c | 42 ++++++++++++++++++++++--------------------
5 files changed, 56 insertions(+), 61 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3370a8c..6d40cc8 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -137,12 +137,14 @@ enum lru_list {
LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
LRU_UNEVICTABLE,
- NR_LRU_LISTS
+ NR_LRU_LISTS,
+ NR_EVICTABLE_LRU_LISTS = LRU_UNEVICTABLE,
};

#define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)

-#define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
+#define for_each_evictable_lru(lru) \
+ for (lru = 0; lru < NR_EVICTABLE_LRU_LISTS; lru++)

static inline int is_file_lru(enum lru_list lru)
{
@@ -165,11 +167,8 @@ struct zone_reclaim_stat {
* mem/swap backed and file backed pages are refeferenced.
* The higher the rotated/scanned ratio, the more valuable
* that cache is.
- *
- * The anon LRU stats live in [0], file LRU stats in [1]
*/
- unsigned long recent_rotated[2];
- unsigned long recent_scanned[2];
+ unsigned long recent_rotated[NR_EVICTABLE_LRU_LISTS];
};

struct lruvec {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6864f57..02af4a6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4183,26 +4183,31 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,

#ifdef CONFIG_DEBUG_VM
{
- int nid, zid;
+ int nid, zid, lru;
struct mem_cgroup_per_zone *mz;
struct zone_reclaim_stat *rstat;
- unsigned long recent_rotated[2] = {0, 0};
- unsigned long recent_scanned[2] = {0, 0};
+ unsigned long recent_rotated[NR_EVICTABLE_LRU_LISTS];

+ memset(recent_rotated, 0, sizeof(recent_rotated));
for_each_online_node(nid)
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
mz = mem_cgroup_zoneinfo(memcg, nid, zid);
rstat = &mz->lruvec.reclaim_stat;
-
- recent_rotated[0] += rstat->recent_rotated[0];
- recent_rotated[1] += rstat->recent_rotated[1];
- recent_scanned[0] += rstat->recent_scanned[0];
- recent_scanned[1] += rstat->recent_scanned[1];
+ for_each_evictable_lru(lru)
+ recent_rotated[lru] +=
+ rstat->recent_rotated[lru];
}
- cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
- cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
- cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
- cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
+
+ cb->fill(cb, "recent_rotated_anon",
+ recent_rotated[LRU_ACTIVE_ANON]);
+ cb->fill(cb, "recent_rotated_file",
+ recent_rotated[LRU_ACTIVE_FILE]);
+ cb->fill(cb, "recent_scanned_anon",
+ recent_rotated[LRU_ACTIVE_ANON] +
+ recent_rotated[LRU_INACTIVE_ANON]);
+ cb->fill(cb, "recent_scanned_file",
+ recent_rotated[LRU_ACTIVE_FILE] +
+ recent_rotated[LRU_INACTIVE_FILE]);
}
#endif

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ab2d210..ea40034 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4365,10 +4365,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
zone_pcp_init(zone);
for_each_lru(lru)
INIT_LIST_HEAD(&zone->lruvec.lists[lru]);
- zone->lruvec.reclaim_stat.recent_rotated[0] = 0;
- zone->lruvec.reclaim_stat.recent_rotated[1] = 0;
- zone->lruvec.reclaim_stat.recent_scanned[0] = 0;
- zone->lruvec.reclaim_stat.recent_scanned[1] = 0;
+ memset(&zone->lruvec.reclaim_stat, 0,
+ sizeof(struct zone_reclaim_stat));
zap_zone_vm_stats(zone);
zone->flags = 0;
if (!size)
diff --git a/mm/swap.c b/mm/swap.c
index 60d14da..9051079 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -277,7 +277,7 @@ void rotate_reclaimable_page(struct page *page)
}

static void update_page_reclaim_stat(struct zone *zone, struct page *page,
- int file, int rotated)
+ enum lru_list lru)
{
struct zone_reclaim_stat *reclaim_stat;

@@ -285,9 +285,7 @@ static void update_page_reclaim_stat(struct zone *zone, struct page *page,
if (!reclaim_stat)
reclaim_stat = &zone->lruvec.reclaim_stat;

- reclaim_stat->recent_scanned[file]++;
- if (rotated)
- reclaim_stat->recent_rotated[file]++;
+ reclaim_stat->recent_rotated[lru]++;
}

static void __activate_page(struct page *page, void *arg)
@@ -295,7 +293,6 @@ static void __activate_page(struct page *page, void *arg)
struct zone *zone = page_zone(page);

if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
- int file = page_is_file_cache(page);
int lru = page_lru_base_type(page);
del_page_from_lru_list(zone, page, lru);

@@ -304,7 +301,7 @@ static void __activate_page(struct page *page, void *arg)
add_page_to_lru_list(zone, page, lru);
__count_vm_event(PGACTIVATE);

- update_page_reclaim_stat(zone, page, file, 1);
+ update_page_reclaim_stat(zone, page, lru);
}
}

@@ -482,7 +479,7 @@ static void lru_deactivate_fn(struct page *page, void *arg)

if (active)
__count_vm_event(PGDEACTIVATE);
- update_page_reclaim_stat(zone, page, file, 0);
+ update_page_reclaim_stat(zone, page, lru);
}

/*
@@ -646,9 +643,7 @@ EXPORT_SYMBOL(__pagevec_release);
void lru_add_page_tail(struct zone* zone,
struct page *page, struct page *page_tail)
{
- int uninitialized_var(active);
enum lru_list lru;
- const int file = 0;

VM_BUG_ON(!PageHead(page));
VM_BUG_ON(PageCompound(page_tail));
@@ -660,12 +655,9 @@ void lru_add_page_tail(struct zone* zone,
if (page_evictable(page_tail, NULL)) {
if (PageActive(page)) {
SetPageActive(page_tail);
- active = 1;
lru = LRU_ACTIVE_ANON;
- } else {
- active = 0;
+ } else
lru = LRU_INACTIVE_ANON;
- }
} else {
SetPageUnevictable(page_tail);
lru = LRU_UNEVICTABLE;
@@ -687,8 +679,8 @@ void lru_add_page_tail(struct zone* zone,
list_move_tail(&page_tail->lru, list_head);
}

- if (!PageUnevictable(page))
- update_page_reclaim_stat(zone, page_tail, file, active);
+ if (!is_unevictable_lru(lru))
+ update_page_reclaim_stat(zone, page_tail, lru);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

@@ -696,18 +688,17 @@ static void __pagevec_lru_add_fn(struct page *page, void *arg)
{
enum lru_list lru = (enum lru_list)arg;
struct zone *zone = page_zone(page);
- int file = is_file_lru(lru);
- int active = is_active_lru(lru);

VM_BUG_ON(PageActive(page));
VM_BUG_ON(PageUnevictable(page));
VM_BUG_ON(PageLRU(page));

SetPageLRU(page);
- if (active)
+ if (is_active_lru(lru))
SetPageActive(page);
+
add_page_to_lru_list(zone, page, lru);
- update_page_reclaim_stat(zone, page, file, active);
+ update_page_reclaim_stat(zone, page, lru);
}

/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0966f11..ab5c0f6 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1348,11 +1348,7 @@ putback_inactive_pages(struct mem_cgroup_zone *mz,
SetPageLRU(page);
lru = page_lru(page);
add_page_to_lru_list(zone, page, lru);
- if (is_active_lru(lru)) {
- int file = is_file_lru(lru);
- int numpages = hpage_nr_pages(page);
- reclaim_stat->recent_rotated[file] += numpages;
- }
+ reclaim_stat->recent_rotated[lru] += hpage_nr_pages(page);
if (put_page_testzero(page)) {
__ClearPageLRU(page);
__ClearPageActive(page);
@@ -1533,8 +1529,11 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,

spin_lock_irq(&zone->lru_lock);

- reclaim_stat->recent_scanned[0] += nr_anon;
- reclaim_stat->recent_scanned[1] += nr_file;
+ /*
+ * Count reclaimed pages as rotated, this helps balance scan pressure
+ * between file and anonymous pages in get_scan_ratio.
+ */
+ reclaim_stat->recent_rotated[lru] += nr_reclaimed;

if (current_is_kswapd())
__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
@@ -1672,8 +1671,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
if (global_reclaim(sc))
zone->pages_scanned += nr_scanned;

- reclaim_stat->recent_scanned[file] += nr_taken;
-
__count_zone_vm_events(PGREFILL, zone, nr_scanned);
__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
@@ -1728,7 +1725,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
* helps balance scan pressure between file and anonymous pages in
* get_scan_ratio.
*/
- reclaim_stat->recent_rotated[file] += nr_rotated;
+ reclaim_stat->recent_rotated[lru] += nr_rotated;

move_active_pages_to_lru(zone, &l_active, &l_hold, lru);
move_active_pages_to_lru(zone, &l_inactive, &l_hold, lru - LRU_ACTIVE);
@@ -1861,6 +1858,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
unsigned long anon_prio, file_prio;
unsigned long ap, fp;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
+ unsigned long *recent_rotated = reclaim_stat->recent_rotated;
u64 fraction[2], denominator;
enum lru_list lru;
int noswap = 0;
@@ -1926,14 +1924,16 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
* anon in [0], file in [1]
*/
spin_lock_irq(&mz->zone->lru_lock);
- if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
- reclaim_stat->recent_scanned[0] /= 2;
- reclaim_stat->recent_rotated[0] /= 2;
+ if (unlikely(recent_rotated[LRU_INACTIVE_ANON] +
+ recent_rotated[LRU_ACTIVE_ANON] > anon / 4)) {
+ recent_rotated[LRU_INACTIVE_ANON] /= 2;
+ recent_rotated[LRU_ACTIVE_ANON] /= 2;
}

- if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
- reclaim_stat->recent_scanned[1] /= 2;
- reclaim_stat->recent_rotated[1] /= 2;
+ if (unlikely(recent_rotated[LRU_INACTIVE_FILE] +
+ recent_rotated[LRU_ACTIVE_FILE] > file / 4)) {
+ recent_rotated[LRU_INACTIVE_FILE] /= 2;
+ recent_rotated[LRU_ACTIVE_FILE] /= 2;
}

/*
@@ -1941,11 +1941,13 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
* proportional to the fraction of recently scanned pages on
* each list that were recently referenced and in active use.
*/
- ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
- ap /= reclaim_stat->recent_rotated[0] + 1;
+ ap = (anon_prio + 1) * (recent_rotated[LRU_INACTIVE_ANON] +
+ recent_rotated[LRU_ACTIVE_ANON] + 1);
+ ap /= recent_rotated[LRU_ACTIVE_ANON] + 1;

- fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
- fp /= reclaim_stat->recent_rotated[1] + 1;
+ fp = (file_prio + 1) * (recent_rotated[LRU_INACTIVE_FILE] +
+ recent_rotated[LRU_ACTIVE_FILE] + 1);
+ fp /= recent_rotated[LRU_ACTIVE_FILE] + 1;
spin_unlock_irq(&mz->zone->lru_lock);

fraction[0] = ap;


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