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    Subject[PATCH 08/10] vmscan: Setup pagevec as late as possible in shrink_inactive_list()
    Date
    shrink_inactive_list() sets up a pagevec to release unfreeable pages. It
    uses significant amounts of stack doing this. This patch splits
    shrink_inactive_list() to take the stack usage out of the main path so
    that callers to writepage() do not contain an unused pagevec on the
    stack.

    Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    ---
    mm/vmscan.c | 93 +++++++++++++++++++++++++++++++++-------------------------
    1 files changed, 53 insertions(+), 40 deletions(-)

    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index a232ad6..9bc1ede 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -1120,6 +1120,54 @@ static int too_many_isolated(struct zone *zone, int file,
    }

    /*
    + * TODO: Try merging with migrations version of putback_lru_pages
    + */
    +static noinline void putback_lru_pages(struct zone *zone,
    + struct zone_reclaim_stat *reclaim_stat,
    + unsigned long nr_anon, unsigned long nr_file,
    + struct list_head *page_list)
    +{
    + struct page *page;
    + struct pagevec pvec;
    +
    + pagevec_init(&pvec, 1);
    +
    + /*
    + * Put back any unfreeable pages.
    + */
    + spin_lock(&zone->lru_lock);
    + while (!list_empty(page_list)) {
    + int lru;
    + page = lru_to_page(page_list);
    + VM_BUG_ON(PageLRU(page));
    + list_del(&page->lru);
    + if (unlikely(!page_evictable(page, NULL))) {
    + spin_unlock_irq(&zone->lru_lock);
    + putback_lru_page(page);
    + spin_lock_irq(&zone->lru_lock);
    + continue;
    + }
    + 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);
    + reclaim_stat->recent_rotated[file]++;
    + }
    + if (!pagevec_add(&pvec, page)) {
    + spin_unlock_irq(&zone->lru_lock);
    + __pagevec_release(&pvec);
    + spin_lock_irq(&zone->lru_lock);
    + }
    + }
    + __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
    + __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
    +
    + spin_unlock_irq(&zone->lru_lock);
    + pagevec_release(&pvec);
    +}
    +
    +/*
    * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
    * of reclaimed pages
    */
    @@ -1128,12 +1176,10 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
    int file)
    {
    LIST_HEAD(page_list);
    - struct pagevec pvec;
    unsigned long nr_scanned;
    unsigned long nr_reclaimed = 0;
    struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
    int lumpy_reclaim = 0;
    - struct page *page;
    unsigned long nr_taken;
    unsigned long nr_active;
    unsigned int count[NR_LRU_LISTS] = { 0, };
    @@ -1160,8 +1206,6 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
    else if (sc->order && sc->priority < DEF_PRIORITY - 2)
    lumpy_reclaim = 1;

    - pagevec_init(&pvec, 1);
    -
    lru_add_drain();
    spin_lock_irq(&zone->lru_lock);
    nr_taken = sc->isolate_pages(nr_to_scan,
    @@ -1177,8 +1221,10 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
    __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
    }

    - if (nr_taken == 0)
    - goto done;
    + if (nr_taken == 0) {
    + spin_unlock_irq(&zone->lru_lock);
    + return 0;
    + }

    nr_active = clear_active_flags(&page_list, count);
    __count_vm_events(PGDEACTIVATE, nr_active);
    @@ -1229,40 +1275,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
    __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
    __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);

    - spin_lock(&zone->lru_lock);
    - /*
    - * Put back any unfreeable pages.
    - */
    - while (!list_empty(&page_list)) {
    - int lru;
    - page = lru_to_page(&page_list);
    - VM_BUG_ON(PageLRU(page));
    - list_del(&page->lru);
    - if (unlikely(!page_evictable(page, NULL))) {
    - spin_unlock_irq(&zone->lru_lock);
    - putback_lru_page(page);
    - spin_lock_irq(&zone->lru_lock);
    - continue;
    - }
    - 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);
    - reclaim_stat->recent_rotated[file]++;
    - }
    - if (!pagevec_add(&pvec, page)) {
    - spin_unlock_irq(&zone->lru_lock);
    - __pagevec_release(&pvec);
    - spin_lock_irq(&zone->lru_lock);
    - }
    - }
    - __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
    - __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
    -
    -done:
    - spin_unlock_irq(&zone->lru_lock);
    - pagevec_release(&pvec);
    + putback_lru_pages(zone, reclaim_stat, nr_anon, nr_file, &page_list);
    return nr_reclaimed;
    }

    --
    1.6.5


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