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    Subject[PATCH 01/10] mm: workingset: don't drop refault information prematurely
    Date
    From: Johannes Weiner <jweiner@fb.com>

    If we just keep enough refault information to match the CURRENT page
    cache during reclaim time, we could lose a lot of events when there is
    only a temporary spike in non-cache memory consumption that pushes out
    all the cache. Once cache comes back, we won't see those refaults.
    They might not be actionable for LRU aging, but we want to know about
    them for measuring memory pressure.

    Signed-off-by: Johannes Weiner <jweiner@fb.com>
    ---
    mm/workingset.c | 18 +++++++++---------
    1 file changed, 9 insertions(+), 9 deletions(-)

    diff --git a/mm/workingset.c b/mm/workingset.c
    index 40ee02c83978..53759a3cf99a 100644
    --- a/mm/workingset.c
    +++ b/mm/workingset.c
    @@ -364,7 +364,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
    {
    unsigned long max_nodes;
    unsigned long nodes;
    - unsigned long cache;
    + unsigned long pages;

    /* list_lru lock nests inside the IRQ-safe i_pages lock */
    local_irq_disable();
    @@ -393,14 +393,14 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
    *
    * PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
    */
    - if (sc->memcg) {
    - cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
    - LRU_ALL_FILE);
    - } else {
    - cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
    - node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
    - }
    - max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
    +#ifdef CONFIG_MEMCG
    + if (sc->memcg)
    + pages = page_counter_read(&sc->memcg->memory);
    + else
    +#endif
    + pages = node_present_pages(sc->nid);
    +
    + max_nodes = pages >> (RADIX_TREE_MAP_SHIFT - 3);

    if (nodes <= max_nodes)
    return 0;
    --
    2.18.0
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