From: Johannes Weiner <han...@cmpxchg.org>

Pages are now uncharged at release time, and all sources of batched
uncharges operate on lists of pages.  Directly use those lists, and
get rid of the per-task batching state.

This also batches statistics accounting, in addition to the res
counter charges, to reduce IRQ-disabling and re-enabling.

Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Michal Hocko <mho...@suse.cz>
Cc: Hugh Dickins <hu...@google.com>
Cc: Tejun Heo <t...@kernel.org>
Cc: Vladimir Davydov <vdavy...@parallels.com>
Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Cc: Vladimir Davydov <vdavy...@parallels.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>

https://jira.sw.ru/browse/PSBM-51558
(cherry picked from commit 747db954cab64c6b7a95b121b517165f34751898)
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
---
 include/linux/memcontrol.h |  12 +--
 include/linux/sched.h      |   6 --
 kernel/fork.c              |   4 -
 mm/memcontrol.c            | 204 ++++++++++++++++++++++++---------------------
 mm/swap.c                  |  12 +--
 mm/vmscan.c                |  12 ++-
 6 files changed, 122 insertions(+), 128 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ca343bf..681f320 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -51,12 +51,8 @@ int mem_cgroup_try_charge(struct page *page, struct 
mm_struct *mm,
 void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg,
                              bool lrucare);
 void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg);
-
 void mem_cgroup_uncharge(struct page *page);
-
-/* Batched uncharging */
-void mem_cgroup_uncharge_start(void);
-void mem_cgroup_uncharge_end(void);
+void mem_cgroup_uncharge_list(struct list_head *page_list);
 
 void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
                        bool lrucare);
@@ -244,11 +240,7 @@ static inline void mem_cgroup_uncharge(struct page *page)
 {
 }
 
-static inline void mem_cgroup_uncharge_start(void)
-{
-}
-
-static inline void mem_cgroup_uncharge_end(void)
+static inline void mem_cgroup_uncharge_list(struct list_head *page_list)
 {
 }
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 05a4b12..c945d93 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1721,12 +1721,6 @@ struct task_struct {
        struct ve_struct *task_ve;
 #endif
 #ifdef CONFIG_MEMCG /* memcg uses this to do batch job */
-       struct memcg_batch_info {
-               int do_batch;   /* incremented when batch uncharge started */
-               struct mem_cgroup *memcg; /* target memcg of uncharge */
-               unsigned long nr_pages; /* uncharged usage */
-               unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
-       } memcg_batch;
        unsigned int memcg_kmem_skip_account;
 #endif
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
diff --git a/kernel/fork.c b/kernel/fork.c
index 99e39cc..329dc42 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1453,10 +1453,6 @@ static struct task_struct *copy_process(unsigned long 
clone_flags,
 #ifdef CONFIG_DEBUG_MUTEXES
        p->blocked_on = NULL; /* not blocked yet */
 #endif
-#ifdef CONFIG_MEMCG
-       p->memcg_batch.do_batch = 0;
-       p->memcg_batch.memcg = NULL;
-#endif
 #ifdef CONFIG_BCACHE
        p->sequential_io        = 0;
        p->sequential_io_avg    = 0;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1eb0e85..16bb6aa 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3625,51 +3625,6 @@ out:
        return ret;
 }
 
-/*
- * Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
- * In that cases, pages are freed continuously and we can expect pages
- * are in the same memcg. All these calls itself limits the number of
- * pages freed at once, then uncharge_start/end() is called properly.
- * This may be called prural(2) times in a context,
- */
-
-void mem_cgroup_uncharge_start(void)
-{
-       unsigned long flags;
-
-       local_irq_save(flags);
-       current->memcg_batch.do_batch++;
-       /* We can do nest. */
-       if (current->memcg_batch.do_batch == 1) {
-               current->memcg_batch.memcg = NULL;
-               current->memcg_batch.nr_pages = 0;
-               current->memcg_batch.memsw_nr_pages = 0;
-       }
-       local_irq_restore(flags);
-}
-
-void mem_cgroup_uncharge_end(void)
-{
-       struct memcg_batch_info *batch = &current->memcg_batch;
-       unsigned long flags;
-
-       local_irq_save(flags);
-       VM_BUG_ON(!batch->do_batch);
-       if (--batch->do_batch) /* If stacked, do nothing */
-               goto out;
-       /*
-        * This "batch->memcg" is valid without any css_get/put etc...
-        * bacause we hide charges behind us.
-        */
-       if (batch->nr_pages)
-               page_counter_uncharge(&batch->memcg->memory, batch->nr_pages);
-       if (batch->memsw_nr_pages)
-               page_counter_uncharge(&batch->memcg->memsw, 
batch->memsw_nr_pages);
-       memcg_oom_recover(batch->memcg);
-out:
-       local_irq_restore(flags);
-}
-
 #ifdef CONFIG_MEMCG_SWAP
 static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
                                         bool charge)
@@ -6957,6 +6912,98 @@ void mem_cgroup_cancel_charge(struct page *page, struct 
mem_cgroup *memcg)
        cancel_charge(memcg, nr_pages);
 }
 
+static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
+                          unsigned long nr_mem, unsigned long nr_memsw,
+                          unsigned long nr_anon, unsigned long nr_file,
+                          unsigned long nr_huge, struct page *dummy_page)
+{
+       unsigned long flags;
+
+       if (nr_mem)
+               page_counter_uncharge(&memcg->memory, nr_mem);
+       if (nr_memsw)
+               page_counter_uncharge(&memcg->memsw, nr_memsw);
+
+       memcg_oom_recover(memcg);
+
+       local_irq_save(flags);
+       __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS], nr_anon);
+       __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_CACHE], nr_file);
+       __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE], nr_huge);
+       __this_cpu_add(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT], pgpgout);
+       __this_cpu_add(memcg->stat->nr_page_events, nr_anon + nr_file);
+       memcg_check_events(memcg, dummy_page);
+       local_irq_restore(flags);
+}
+
+static void uncharge_list(struct list_head *page_list)
+{
+       struct mem_cgroup *memcg = NULL;
+       unsigned long nr_memsw = 0;
+       unsigned long nr_anon = 0;
+       unsigned long nr_file = 0;
+       unsigned long nr_huge = 0;
+       unsigned long pgpgout = 0;
+       unsigned long nr_mem = 0;
+       struct list_head *next;
+       struct page *page;
+
+       next = page_list->next;
+       do {
+               unsigned int nr_pages = 1;
+               struct page_cgroup *pc;
+
+               page = list_entry(next, struct page, lru);
+               next = page->lru.next;
+
+               VM_BUG_ON_PAGE(PageLRU(page), page);
+               VM_BUG_ON_PAGE(page_count(page), page);
+
+               pc = lookup_page_cgroup(page);
+               if (!PageCgroupUsed(pc))
+                       continue;
+
+               /*
+                * Nobody should be changing or seriously looking at
+                * pc->mem_cgroup and pc->flags at this point, we have
+                * fully exclusive access to the page.
+                */
+
+               if (memcg != pc->mem_cgroup) {
+                       if (memcg) {
+                               uncharge_batch(memcg, pgpgout, nr_mem, nr_memsw,
+                                              nr_anon, nr_file, nr_huge, page);
+                               pgpgout = nr_mem = nr_memsw = 0;
+                               nr_anon = nr_file = nr_huge = 0;
+                       }
+                       memcg = pc->mem_cgroup;
+               }
+
+               if (PageTransHuge(page)) {
+                       nr_pages <<= compound_order(page);
+                       VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+                       nr_huge += nr_pages;
+               }
+
+               if (PageAnon(page))
+                       nr_anon += nr_pages;
+               else
+                       nr_file += nr_pages;
+
+               if (pc->flags & PCG_MEM)
+                       nr_mem += nr_pages;
+               if (pc->flags & PCG_MEMSW)
+                       nr_memsw += nr_pages;
+               pc->flags = 0;
+
+               pgpgout++;
+       } while (next != page_list);
+
+       if (memcg)
+               uncharge_batch(memcg, pgpgout, nr_mem, nr_memsw,
+                              nr_anon, nr_file, nr_huge, page);
+}
+
 /**
  * mem_cgroup_uncharge - uncharge a page
  * @page: page to uncharge
@@ -6966,67 +7013,34 @@ void mem_cgroup_cancel_charge(struct page *page, struct 
mem_cgroup *memcg)
  */
 void mem_cgroup_uncharge(struct page *page)
 {
-       struct memcg_batch_info *batch;
-       unsigned int nr_pages = 1;
-       struct mem_cgroup *memcg;
        struct page_cgroup *pc;
-       unsigned long pc_flags;
-       unsigned long flags;
-
-       VM_BUG_ON_PAGE(PageLRU(page), page);
-       VM_BUG_ON_PAGE(page_count(page), page);
 
        if (mem_cgroup_disabled())
                return;
 
+       /* Don't touch page->lru of any random page, pre-check: */
        pc = lookup_page_cgroup(page);
-
-       /* Every final put_page() ends up here */
        if (!PageCgroupUsed(pc))
                return;
 
-       if (PageTransHuge(page)) {
-               nr_pages <<= compound_order(page);
-               VM_BUG_ON_PAGE(!PageTransHuge(page), page);
-       }
-       /*
-        * Nobody should be changing or seriously looking at
-        * pc->mem_cgroup and pc->flags at this point, we have fully
-        * exclusive access to the page.
-        */
-       memcg = pc->mem_cgroup;
-       pc_flags = pc->flags;
-       pc->flags = 0;
-
-       local_irq_save(flags);
+       INIT_LIST_HEAD(&page->lru);
+       uncharge_list(&page->lru);
+}
 
-       if (nr_pages > 1)
-               goto direct;
-       if (unlikely(test_thread_flag(TIF_MEMDIE)))
-               goto direct;
-       batch = &current->memcg_batch;
-       if (!batch->do_batch)
-               goto direct;
-       if (batch->memcg && batch->memcg != memcg)
-               goto direct;
-       if (!batch->memcg)
-               batch->memcg = memcg;
-       if (pc_flags & PCG_MEM)
-               batch->nr_pages++;
-       if (pc_flags & PCG_MEMSW)
-               batch->memsw_nr_pages++;
-       goto out;
-direct:
-       if (pc_flags & PCG_MEM)
-               page_counter_uncharge(&memcg->memory, nr_pages);
-       if (pc_flags & PCG_MEMSW)
-               page_counter_uncharge(&memcg->memsw, nr_pages);
-       memcg_oom_recover(memcg);
-out:
-       mem_cgroup_charge_statistics(memcg, page, -nr_pages);
-       memcg_check_events(memcg, page);
+/**
+ * mem_cgroup_uncharge_list - uncharge a list of page
+ * @page_list: list of pages to uncharge
+ *
+ * Uncharge a list of pages previously charged with
+ * mem_cgroup_try_charge() and mem_cgroup_commit_charge().
+ */
+void mem_cgroup_uncharge_list(struct list_head *page_list)
+{
+       if (mem_cgroup_disabled())
+               return;
 
-       local_irq_restore(flags);
+       if (!list_empty(page_list))
+               uncharge_list(page_list);
 }
 
 /**
diff --git a/mm/swap.c b/mm/swap.c
index 865375c..19caa19 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -928,8 +928,6 @@ void release_pages(struct page **pages, int nr, bool cold)
        unsigned long uninitialized_var(flags);
        unsigned int uninitialized_var(lock_batch);
 
-       mem_cgroup_uncharge_start();
-
        for (i = 0; i < nr; i++) {
                struct page *page = pages[i];
                const bool was_thp = is_trans_huge_page_release(page);
@@ -1025,7 +1023,6 @@ void release_pages(struct page **pages, int nr, bool cold)
                        __ClearPageLRU(page);
                        del_page_from_lru_list(page, lruvec, 
page_off_lru(page));
                }
-               mem_cgroup_uncharge(page);
 
                if (!was_thp) {
                        /*
@@ -1041,12 +1038,15 @@ void release_pages(struct page **pages, int nr, bool 
cold)
        if (zone)
                spin_unlock_irqrestore(&zone->lru_lock, flags);
 
-       mem_cgroup_uncharge_end();
-       if (!list_empty(&pages_to_free))
+       if (!list_empty(&pages_to_free)) {
+               mem_cgroup_uncharge_list(&pages_to_free);
                free_hot_cold_page_list(&pages_to_free, cold);
+       }
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-       if (!list_empty(&trans_huge_pages_to_free))
+       if (!list_empty(&trans_huge_pages_to_free)) {
+               mem_cgroup_uncharge_list(&trans_huge_pages_to_free);
                free_trans_huge_page_list(&trans_huge_pages_to_free);
+       }
 #endif
 }
 EXPORT_SYMBOL(release_pages);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6987a4b..194c2a2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -851,7 +851,6 @@ static unsigned long shrink_page_list(struct list_head 
*page_list,
 
        cond_resched();
 
-       mem_cgroup_uncharge_start();
        while (!list_empty(page_list)) {
                struct address_space *mapping;
                struct page *page;
@@ -1135,7 +1134,6 @@ static unsigned long shrink_page_list(struct list_head 
*page_list,
                 */
                __clear_page_locked(page);
 free_it:
-               mem_cgroup_uncharge(page);
                nr_reclaimed++;
 
                /*
@@ -1165,8 +1163,8 @@ keep:
                list_add(&page->lru, &ret_pages);
                VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
        }
-       mem_cgroup_uncharge_end();
 
+       mem_cgroup_uncharge_list(&free_pages);
        try_to_unmap_flush();
        free_hot_cold_page_list(&free_pages, true);
 
@@ -1488,10 +1486,9 @@ putback_inactive_pages(struct lruvec *lruvec, struct 
list_head *page_list)
                        __ClearPageActive(page);
                        del_page_from_lru_list(page, lruvec, lru);
 
-                       mem_cgroup_uncharge(page);
-
                        if (unlikely(PageCompound(page))) {
                                spin_unlock_irq(&zone->lru_lock);
+                               mem_cgroup_uncharge(page);
                                (*get_compound_page_dtor(page))(page);
                                spin_lock_irq(&zone->lru_lock);
                        } else
@@ -1586,6 +1583,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct 
lruvec *lruvec,
 
        spin_unlock_irq(&zone->lru_lock);
 
+       mem_cgroup_uncharge_list(&page_list);
        free_hot_cold_page_list(&page_list, true);
 
        /*
@@ -1697,10 +1695,9 @@ static void move_active_pages_to_lru(struct lruvec 
*lruvec,
                        __ClearPageActive(page);
                        del_page_from_lru_list(page, lruvec, lru);
 
-                       mem_cgroup_uncharge(page);
-
                        if (unlikely(PageCompound(page))) {
                                spin_unlock_irq(&zone->lru_lock);
+                               mem_cgroup_uncharge(page);
                                (*get_compound_page_dtor(page))(page);
                                spin_lock_irq(&zone->lru_lock);
                        } else
@@ -1810,6 +1807,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
        __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
        spin_unlock_irq(&zone->lru_lock);
 
+       mem_cgroup_uncharge_list(&l_hold);
        free_hot_cold_page_list(&l_hold, true);
 
        KSTAT_PERF_LEAVE(refill_inact);
-- 
2.10.2

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