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    Subject[patch 3/3] mm: vmscan: clean up struct scan_control
    Date
    Reorder the members by input and output, then turn the individual
    integers for may_writepage, may_unmap, may_swap, compaction_ready,
    hibernation_mode into flags that fit into a single integer.

    Stack delta: +72/-296 -224 old new delta
    kswapd 104 176 +72
    try_to_free_pages 80 56 -24
    try_to_free_mem_cgroup_pages 80 56 -24
    shrink_all_memory 88 64 -24
    reclaim_clean_pages_from_list 168 144 -24
    mem_cgroup_shrink_node_zone 104 80 -24
    __zone_reclaim 176 152 -24
    balance_pgdat 152 - -152

    text data bss dec hex filename
    38151 5641 16 43808 ab20 mm/vmscan.o.old
    38047 5641 16 43704 aab8 mm/vmscan.o

    Suggested-by: Mel Gorman <mgorman@suse.de>
    Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
    ---
    mm/vmscan.c | 158 ++++++++++++++++++++++++++++++------------------------------
    1 file changed, 78 insertions(+), 80 deletions(-)

    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index c28b8981e56a..73d8e69ff3eb 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -58,36 +58,28 @@
    #define CREATE_TRACE_POINTS
    #include <trace/events/vmscan.h>

    -struct scan_control {
    - /* Incremented by the number of inactive pages that were scanned */
    - unsigned long nr_scanned;
    -
    - /* Number of pages freed so far during a call to shrink_zones() */
    - unsigned long nr_reclaimed;
    -
    - /* One of the zones is ready for compaction */
    - int compaction_ready;
    +/* Scan control flags */
    +#define MAY_WRITEPAGE 0x1
    +#define MAY_UNMAP 0x2
    +#define MAY_SWAP 0x4
    +#define MAY_SKIP_CONGESTION 0x8
    +#define COMPACTION_READY 0x10

    +struct scan_control {
    /* How many pages shrink_list() should reclaim */
    unsigned long nr_to_reclaim;

    - unsigned long hibernation_mode;
    -
    /* This context's GFP mask */
    gfp_t gfp_mask;

    - int may_writepage;
    -
    - /* Can mapped pages be reclaimed? */
    - int may_unmap;
    -
    - /* Can pages be swapped as part of reclaim? */
    - int may_swap;
    -
    + /* Allocation order */
    int order;

    - /* Scan (total_size >> priority) pages at once */
    - int priority;
    + /*
    + * Nodemask of nodes allowed by the caller. If NULL, all nodes
    + * are scanned.
    + */
    + nodemask_t *nodemask;

    /*
    * The memory cgroup that hit its limit and as a result is the
    @@ -95,11 +87,17 @@ struct scan_control {
    */
    struct mem_cgroup *target_mem_cgroup;

    - /*
    - * Nodemask of nodes allowed by the caller. If NULL, all nodes
    - * are scanned.
    - */
    - nodemask_t *nodemask;
    + /* Scan (total_size >> priority) pages at once */
    + int priority;
    +
    + /* Scan control flags; see above */
    + unsigned int flags;
    +
    + /* Incremented by the number of inactive pages that were scanned */
    + unsigned long nr_scanned;
    +
    + /* Number of pages freed so far during a call to shrink_zones() */
    + unsigned long nr_reclaimed;
    };

    #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
    @@ -840,7 +838,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
    if (unlikely(!page_evictable(page)))
    goto cull_mlocked;

    - if (!sc->may_unmap && page_mapped(page))
    + if (!(sc->flags & MAY_UNMAP) && page_mapped(page))
    goto keep_locked;

    /* Double the slab pressure for mapped and swapcache pages */
    @@ -1014,7 +1012,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
    goto keep_locked;
    if (!may_enter_fs)
    goto keep_locked;
    - if (!sc->may_writepage)
    + if (!(sc->flags & MAY_WRITEPAGE))
    goto keep_locked;

    /* Page is dirty, try to write it out here */
    @@ -1146,7 +1144,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
    struct scan_control sc = {
    .gfp_mask = GFP_KERNEL,
    .priority = DEF_PRIORITY,
    - .may_unmap = 1,
    + .flags = MAY_UNMAP,
    };
    unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
    struct page *page, *next;
    @@ -1489,9 +1487,9 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,

    lru_add_drain();

    - if (!sc->may_unmap)
    + if (!(sc->flags & MAY_UNMAP))
    isolate_mode |= ISOLATE_UNMAPPED;
    - if (!sc->may_writepage)
    + if (!(sc->flags & MAY_WRITEPAGE))
    isolate_mode |= ISOLATE_CLEAN;

    spin_lock_irq(&zone->lru_lock);
    @@ -1593,7 +1591,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
    * is congested. Allow kswapd to continue until it starts encountering
    * unqueued dirty pages or cycling through the LRU too quickly.
    */
    - if (!sc->hibernation_mode && !current_is_kswapd() &&
    + if (!(sc->flags & MAY_SKIP_CONGESTION) && !current_is_kswapd() &&
    current_may_throttle())
    wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);

    @@ -1683,9 +1681,9 @@ static void shrink_active_list(unsigned long nr_to_scan,

    lru_add_drain();

    - if (!sc->may_unmap)
    + if (!(sc->flags & MAY_UNMAP))
    isolate_mode |= ISOLATE_UNMAPPED;
    - if (!sc->may_writepage)
    + if (!(sc->flags & MAY_WRITEPAGE))
    isolate_mode |= ISOLATE_CLEAN;

    spin_lock_irq(&zone->lru_lock);
    @@ -1897,7 +1895,7 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness,
    force_scan = true;

    /* If we have no swap space, do not bother scanning anon pages. */
    - if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
    + if (!(sc->flags & MAY_SWAP) || (get_nr_swap_pages() <= 0)) {
    scan_balance = SCAN_FILE;
    goto out;
    }
    @@ -2406,7 +2404,7 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
    zonelist_zone_idx(z) <= requested_highidx &&
    compaction_ready(zone, sc->order)) {
    - sc->compaction_ready = true;
    + sc->flags |= COMPACTION_READY;
    continue;
    }

    @@ -2496,7 +2494,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
    if (sc->nr_reclaimed >= sc->nr_to_reclaim)
    break;

    - if (sc->compaction_ready)
    + if (sc->flags & COMPACTION_READY)
    break;

    /*
    @@ -2504,7 +2502,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
    * writepage even in laptop mode.
    */
    if (sc->priority < DEF_PRIORITY - 2)
    - sc->may_writepage = 1;
    + sc->flags |= MAY_WRITEPAGE;

    /*
    * Try to write back as many pages as we just scanned. This
    @@ -2517,7 +2515,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
    if (total_scanned > writeback_threshold) {
    wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
    WB_REASON_TRY_TO_FREE_PAGES);
    - sc->may_writepage = 1;
    + sc->flags |= MAY_WRITEPAGE;
    }
    } while (--sc->priority >= 0);

    @@ -2527,7 +2525,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
    return sc->nr_reclaimed;

    /* Aborted reclaim to try compaction? don't OOM, then */
    - if (sc->compaction_ready)
    + if (sc->flags & COMPACTION_READY)
    return 1;

    /* Any of the zones still reclaimable? Don't OOM. */
    @@ -2668,17 +2666,17 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
    {
    unsigned long nr_reclaimed;
    struct scan_control sc = {
    - .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
    - .may_writepage = !laptop_mode,
    .nr_to_reclaim = SWAP_CLUSTER_MAX,
    - .may_unmap = 1,
    - .may_swap = 1,
    + .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
    .order = order,
    - .priority = DEF_PRIORITY,
    - .target_mem_cgroup = NULL,
    .nodemask = nodemask,
    + .priority = DEF_PRIORITY,
    + .flags = MAY_UNMAP | MAY_SWAP,
    };

    + if (!laptop_mode)
    + sc.flags |= MAY_WRITEPAGE;
    +
    /*
    * Do not enter reclaim if fatal signal was delivered while throttled.
    * 1 is returned so that the page allocator does not OOM kill at this
    @@ -2688,7 +2686,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
    return 1;

    trace_mm_vmscan_direct_reclaim_begin(order,
    - sc.may_writepage,
    + sc.flags & MAY_WRITEPAGE,
    gfp_mask);

    nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
    @@ -2706,23 +2704,22 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
    unsigned long *nr_scanned)
    {
    struct scan_control sc = {
    - .nr_scanned = 0,
    .nr_to_reclaim = SWAP_CLUSTER_MAX,
    - .may_writepage = !laptop_mode,
    - .may_unmap = 1,
    - .may_swap = !noswap,
    - .order = 0,
    - .priority = 0,
    + .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
    + (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
    .target_mem_cgroup = memcg,
    + .flags = MAY_UNMAP,
    };
    struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
    int swappiness = mem_cgroup_swappiness(memcg);

    - sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
    - (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
    + if (!laptop_mode)
    + sc.flags |= MAY_WRITEPAGE;
    + if (!noswap)
    + sc.flags |= MAY_SWAP;

    trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
    - sc.may_writepage,
    + sc.flags & MAY_WRITEPAGE,
    sc.gfp_mask);

    /*
    @@ -2748,18 +2745,19 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
    unsigned long nr_reclaimed;
    int nid;
    struct scan_control sc = {
    - .may_writepage = !laptop_mode,
    - .may_unmap = 1,
    - .may_swap = !noswap,
    .nr_to_reclaim = SWAP_CLUSTER_MAX,
    - .order = 0,
    - .priority = DEF_PRIORITY,
    - .target_mem_cgroup = memcg,
    - .nodemask = NULL, /* we don't care the placement */
    .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
    - (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
    + (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
    + .target_mem_cgroup = memcg,
    + .priority = DEF_PRIORITY,
    + .flags = MAY_UNMAP,
    };

    + if (!laptop_mode)
    + sc.flags |= MAY_WRITEPAGE;
    + if (!noswap)
    + sc.flags |= MAY_SWAP;
    +
    /*
    * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
    * take care of from where we get pages. So the node where we start the
    @@ -2770,7 +2768,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
    zonelist = NODE_DATA(nid)->node_zonelists;

    trace_mm_vmscan_memcg_reclaim_begin(0,
    - sc.may_writepage,
    + sc.flags & MAY_WRITEPAGE,
    sc.gfp_mask);

    nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
    @@ -3015,15 +3013,15 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
    unsigned long nr_soft_scanned;
    struct scan_control sc = {
    .gfp_mask = GFP_KERNEL,
    - .priority = DEF_PRIORITY,
    - .may_unmap = 1,
    - .may_swap = 1,
    - .may_writepage = !laptop_mode,
    .order = order,
    - .target_mem_cgroup = NULL,
    + .priority = DEF_PRIORITY,
    + .flags = MAY_UNMAP | MAY_SWAP,
    };
    count_vm_event(PAGEOUTRUN);

    + if (!laptop_mode)
    + sc.flags |= MAY_WRITEPAGE;
    +
    do {
    unsigned long lru_pages = 0;
    unsigned long nr_attempted = 0;
    @@ -3104,7 +3102,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
    * even in laptop mode.
    */
    if (sc.priority < DEF_PRIORITY - 2)
    - sc.may_writepage = 1;
    + sc.flags |= MAY_WRITEPAGE;

    /*
    * Now scan the zone in the dma->highmem direction, stopping
    @@ -3401,14 +3399,11 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
    {
    struct reclaim_state reclaim_state;
    struct scan_control sc = {
    - .gfp_mask = GFP_HIGHUSER_MOVABLE,
    - .may_swap = 1,
    - .may_unmap = 1,
    - .may_writepage = 1,
    .nr_to_reclaim = nr_to_reclaim,
    - .hibernation_mode = 1,
    - .order = 0,
    + .gfp_mask = GFP_HIGHUSER_MOVABLE,
    .priority = DEF_PRIORITY,
    + .flags = MAY_WRITEPAGE | MAY_UNMAP | MAY_SWAP |
    + MAY_SKIP_CONGESTION,
    };
    struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
    struct task_struct *p = current;
    @@ -3588,19 +3583,22 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
    struct task_struct *p = current;
    struct reclaim_state reclaim_state;
    struct scan_control sc = {
    - .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
    - .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
    - .may_swap = 1,
    .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
    .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
    .order = order,
    .priority = ZONE_RECLAIM_PRIORITY,
    + .flags = MAY_SWAP,
    };
    struct shrink_control shrink = {
    .gfp_mask = sc.gfp_mask,
    };
    unsigned long nr_slab_pages0, nr_slab_pages1;

    + if (zone_reclaim_mode & RECLAIM_WRITE)
    + sc.flags |= MAY_WRITEPAGE;
    + if (zone_reclaim_mode & RECLAIM_SWAP)
    + sc.flags |= MAY_UNMAP;
    +
    cond_resched();
    /*
    * We need to be able to allocate from the reserves for RECLAIM_SWAP
    --
    2.0.0


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