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    Subject[PATCH v3 20/21] mm: split zone->lru_lock
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    Looks like all ready for splitting zone->lru_lock into per-lruvec pieces.

    lruvec locking loop protected with rcu, actually there is irq-disabling instead
    of rcu_read_lock(). Memory controller already releases its lru-vectors after
    syncronize_rcu() in cgroup_diput(). Probably it should be replaced with synchronize_sched()

    Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
    ---
    include/linux/mmzone.h | 3 +-
    mm/compaction.c | 2 +
    mm/internal.h | 66 +++++++++++++++++++++++++-----------------------
    mm/page_alloc.c | 2 +
    mm/swap.c | 2 +
    5 files changed, 40 insertions(+), 35 deletions(-)

    diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
    index 2e3a298..9880150 100644
    --- a/include/linux/mmzone.h
    +++ b/include/linux/mmzone.h
    @@ -304,6 +304,8 @@ struct zone_reclaim_stat {
    };

    struct lruvec {
    + spinlock_t lru_lock;
    +
    struct list_head pages_lru[NR_LRU_LISTS];
    unsigned long pages_count[NR_LRU_COUNTERS];

    @@ -386,7 +388,6 @@ struct zone {
    ZONE_PADDING(_pad1_)

    /* Fields commonly accessed by the page reclaim scanner */
    - spinlock_t lru_lock;
    struct lruvec lruvec;

    unsigned long pages_scanned; /* since last reclaim */
    diff --git a/mm/compaction.c b/mm/compaction.c
    index fa74cbe..8661bb58 100644
    --- a/mm/compaction.c
    +++ b/mm/compaction.c
    @@ -306,7 +306,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
    lruvec = NULL;
    }
    if (need_resched() ||
    - (lruvec && spin_is_contended(&zone->lru_lock))) {
    + (lruvec && spin_is_contended(&lruvec->lru_lock))) {
    if (lruvec)
    unlock_lruvec_irq(lruvec);
    lruvec = NULL;
    diff --git a/mm/internal.h b/mm/internal.h
    index 6dd2e70..9a9fd53 100644
    --- a/mm/internal.h
    +++ b/mm/internal.h
    @@ -15,27 +15,27 @@

    static inline void lock_lruvec(struct lruvec *lruvec, unsigned long *flags)
    {
    - spin_lock_irqsave(&lruvec_zone(lruvec)->lru_lock, *flags);
    + spin_lock_irqsave(&lruvec->lru_lock, *flags);
    }

    static inline void lock_lruvec_irq(struct lruvec *lruvec)
    {
    - spin_lock_irq(&lruvec_zone(lruvec)->lru_lock);
    + spin_lock_irq(&lruvec->lru_lock);
    }

    static inline void unlock_lruvec(struct lruvec *lruvec, unsigned long *flags)
    {
    - spin_unlock_irqrestore(&lruvec_zone(lruvec)->lru_lock, *flags);
    + spin_unlock_irqrestore(&lruvec->lru_lock, *flags);
    }

    static inline void unlock_lruvec_irq(struct lruvec *lruvec)
    {
    - spin_unlock_irq(&lruvec_zone(lruvec)->lru_lock);
    + spin_unlock_irq(&lruvec->lru_lock);
    }

    static inline void wait_lruvec_unlock(struct lruvec *lruvec)
    {
    - spin_unlock_wait(&lruvec_zone(lruvec)->lru_lock);
    + spin_unlock_wait(&lruvec->lru_lock);
    }

    #ifdef CONFIG_CGROUP_MEM_RES_CTLR
    @@ -46,37 +46,39 @@ static inline void wait_lruvec_unlock(struct lruvec *lruvec)
    static inline struct lruvec *__relock_page_lruvec(struct lruvec *locked_lruvec,
    struct page *page)
    {
    - /* Currenyly only one lru_lock per-zone */
    - return page_lruvec(page);
    + struct lruvec *lruvec;
    +
    + do {
    + lruvec = page_lruvec(page);
    + if (likely(lruvec == locked_lruvec))
    + return lruvec;
    + spin_unlock(&locked_lruvec->lru_lock);
    + spin_lock(&lruvec->lru_lock);
    + locked_lruvec = lruvec;
    + } while (1);
    }

    static inline struct lruvec *relock_page_lruvec_irq(struct lruvec *lruvec,
    struct page *page)
    {
    - struct zone *zone = page_zone(page);
    -
    if (!lruvec) {
    - spin_lock_irq(&zone->lru_lock);
    - } else if (zone != lruvec_zone(lruvec)) {
    - unlock_lruvec_irq(lruvec);
    - spin_lock_irq(&zone->lru_lock);
    + local_irq_disable();
    + lruvec = page_lruvec(page);
    + spin_lock(&lruvec->lru_lock);
    }
    - return page_lruvec(page);
    + return __relock_page_lruvec(lruvec, page);
    }

    static inline struct lruvec *relock_page_lruvec(struct lruvec *lruvec,
    struct page *page,
    unsigned long *flags)
    {
    - struct zone *zone = page_zone(page);
    -
    if (!lruvec) {
    - spin_lock_irqsave(&zone->lru_lock, *flags);
    - } else if (zone != lruvec_zone(lruvec)) {
    - unlock_lruvec(lruvec, flags);
    - spin_lock_irqsave(&zone->lru_lock, *flags);
    + local_irq_save(*flags);
    + lruvec = page_lruvec(page);
    + spin_lock(&lruvec->lru_lock);
    }
    - return page_lruvec(page);
    + return __relock_page_lruvec(lruvec, page);
    }

    /*
    @@ -87,22 +89,24 @@ static inline struct lruvec *relock_page_lruvec(struct lruvec *lruvec,
    static inline bool __lock_page_lruvec_irq(struct lruvec **lruvec,
    struct page *page)
    {
    - struct zone *zone;
    bool ret = false;

    + rcu_read_lock();
    + /*
    + * If we see there PageLRU(), it means page has valid lruvec link.
    + * We need protect whole operation with single rcu-interval, otherwise
    + * lruvec which hold this LRU sign can run out before we secure it.
    + */
    if (PageLRU(page)) {
    if (!*lruvec) {
    - zone = page_zone(page);
    - spin_lock_irq(&zone->lru_lock);
    - } else
    - zone = lruvec_zone(*lruvec);
    -
    - if (PageLRU(page)) {
    *lruvec = page_lruvec(page);
    + lock_lruvec_irq(*lruvec);
    + }
    + *lruvec = __relock_page_lruvec(*lruvec, page);
    + if (PageLRU(page))
    ret = true;
    - } else
    - *lruvec = &zone->lruvec;
    }
    + rcu_read_unlock();

    return ret;
    }
    @@ -110,7 +114,7 @@ static inline bool __lock_page_lruvec_irq(struct lruvec **lruvec,
    /* Wait for lruvec unlock before locking other lruvec for the same page */
    static inline void __wait_lruvec_unlock(struct lruvec *lruvec)
    {
    - /* Currently only one lru_lock per-zone */
    + wait_lruvec_unlock(lruvec);
    }

    #else /* CONFIG_CGROUP_MEM_RES_CTLR */
    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index ab42446..beadcc9 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -4294,6 +4294,7 @@ void init_zone_lruvec(struct zone *zone, struct lruvec *lruvec)
    enum lru_list lru;

    memset(lruvec, 0, sizeof(struct lruvec));
    + spin_lock_init(&lruvec->lru_lock);
    for_each_lru(lru)
    INIT_LIST_HEAD(&lruvec->pages_lru[lru]);
    #ifdef CONFIG_CGROUP_MEM_RES_CTLR
    @@ -4369,7 +4370,6 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
    #endif
    zone->name = zone_names[j];
    spin_lock_init(&zone->lock);
    - spin_lock_init(&zone->lru_lock);
    zone_seqlock_init(zone);
    zone->zone_pgdat = pgdat;

    diff --git a/mm/swap.c b/mm/swap.c
    index 998c71c..8156181 100644
    --- a/mm/swap.c
    +++ b/mm/swap.c
    @@ -700,7 +700,7 @@ void lru_add_page_tail(struct lruvec *lruvec,
    VM_BUG_ON(!PageHead(page));
    VM_BUG_ON(PageCompound(page_tail));
    VM_BUG_ON(PageLRU(page_tail));
    - VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
    + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&lruvec->lru_lock));

    SetPageLRU(page_tail);



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