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    Subject[PATCHv23 12/16] mm: trigger page reclaim in alloc_contig_range() to stabilise watermarks
    alloc_contig_range() performs memory allocation so it also should keep
    track on keeping the correct level of memory watermarks. This commit adds
    a call to *_slowpath style reclaim to grab enough pages to make sure that
    the final collection of contiguous pages from freelists will not starve
    the system.

    Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
    Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
    CC: Michal Nazarewicz <mina86@mina86.com>
    Tested-by: Rob Clark <rob.clark@linaro.org>
    Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
    Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
    Tested-by: Robert Nelson <robertcnelson@gmail.com>
    ---
    include/linux/mmzone.h | 9 +++++++
    mm/page_alloc.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 71 insertions(+), 0 deletions(-)

    diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
    index 4781f30..77db8c0 100644
    --- a/include/linux/mmzone.h
    +++ b/include/linux/mmzone.h
    @@ -63,8 +63,10 @@ enum {

    #ifdef CONFIG_CMA
    # define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
    +# define cma_wmark_pages(zone) zone->min_cma_pages
    #else
    # define is_migrate_cma(migratetype) false
    +# define cma_wmark_pages(zone) 0
    #endif

    #define for_each_migratetype_order(order, type) \
    @@ -371,6 +373,13 @@ struct zone {
    /* see spanned/present_pages for more description */
    seqlock_t span_seqlock;
    #endif
    +#ifdef CONFIG_CMA
    + /*
    + * CMA needs to increase watermark levels during the allocation
    + * process to make sure that the system is not starved.
    + */
    + unsigned long min_cma_pages;
    +#endif
    struct free_area free_area[MAX_ORDER];

    #ifndef CONFIG_SPARSEMEM
    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index 7a0d286..39cd74f 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -5092,6 +5092,11 @@ static void __setup_per_zone_wmarks(void)
    low + (min >> 2);
    zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) +
    low + (min >> 1);
    +
    + zone->watermark[WMARK_MIN] += cma_wmark_pages(zone);
    + zone->watermark[WMARK_LOW] += cma_wmark_pages(zone);
    + zone->watermark[WMARK_HIGH] += cma_wmark_pages(zone);
    +
    setup_zone_migrate_reserve(zone);
    spin_unlock_irqrestore(&zone->lock, flags);
    }
    @@ -5695,6 +5700,56 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
    return ret > 0 ? 0 : ret;
    }

    +/*
    + * Update zone's cma pages counter used for watermark level calculation.
    + */
    +static inline void __update_cma_watermarks(struct zone *zone, int count)
    +{
    + unsigned long flags;
    + spin_lock_irqsave(&zone->lock, flags);
    + zone->min_cma_pages += count;
    + spin_unlock_irqrestore(&zone->lock, flags);
    + setup_per_zone_wmarks();
    +}
    +
    +/*
    + * Trigger memory pressure bump to reclaim some pages in order to be able to
    + * allocate 'count' pages in single page units. Does similar work as
    + *__alloc_pages_slowpath() function.
    + */
    +static int __reclaim_pages(struct zone *zone, gfp_t gfp_mask, int count)
    +{
    + enum zone_type high_zoneidx = gfp_zone(gfp_mask);
    + struct zonelist *zonelist = node_zonelist(0, gfp_mask);
    + int did_some_progress = 0;
    + int order = 1;
    + unsigned long watermark;
    +
    + /*
    + * Increase level of watermarks to force kswapd do his job
    + * to stabilise at new watermark level.
    + */
    + __update_cma_watermarks(zone, count);
    +
    + /* Obey watermarks as if the page was being allocated */
    + watermark = low_wmark_pages(zone) + count;
    + while (!zone_watermark_ok(zone, 0, watermark, 0, 0)) {
    + wake_all_kswapd(order, zonelist, high_zoneidx, zone_idx(zone));
    +
    + did_some_progress = __perform_reclaim(gfp_mask, order, zonelist,
    + NULL);
    + if (!did_some_progress) {
    + /* Exhausted what can be done so it's blamo time */
    + out_of_memory(zonelist, gfp_mask, order, NULL);
    + }
    + }
    +
    + /* Restore original watermark levels. */
    + __update_cma_watermarks(zone, -count);
    +
    + return count;
    +}
    +
    /**
    * alloc_contig_range() -- tries to allocate given range of pages
    * @start: start PFN to allocate
    @@ -5793,6 +5848,13 @@ int alloc_contig_range(unsigned long start, unsigned long end,
    goto done;
    }

    + /*
    + * Reclaim enough pages to make sure that contiguous allocation
    + * will not starve the system.
    + */
    + __reclaim_pages(zone, GFP_HIGHUSER_MOVABLE, end-start);
    +
    + /* Grab isolated pages from freelists. */
    outer_end = isolate_freepages_range(outer_start, end);
    if (!outer_end) {
    ret = -EBUSY;
    --
    1.7.1.569.g6f426


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