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    SubjectRe: [PATCH v2 1/1] mm: ALLOC_HIGHATOMIC flag allocation issue
    On Thu,  9 Nov 2023 15:31:33 +0800 Zhiguo Jiang <justinjiang@vivo.com> wrote:

    > Add a new bool* argument to pass return flag instead of *alloc_flags
    > and add the related comments.

    Please retain (and update) the changelog with each version of a patch.

    For reviewers (please), here's the v1 changelog:

    : In case of alloc_flags contain ALLOC_HIGHATOMIC and alloc order
    : is order1/2/3/10 in rmqueue(), if pages are alloced successfully
    : from pcplist cache, and move a free pageblock from the alloced
    : migratetype freelist to MIGRATE_HIGHATOMIC freelist, rather than
    : alloc from MIGRATE_HIGHATOMIC freelist firstly, so this will result
    : in an increasing number of pages on the MIGRATE_HIGHATOMIC freelist,
    : pages in other migratetype freelist are reduced and more likely to
    : allocation failure.
    :
    : Currently the sequence of ALLOC_HIGHATOMIC allocation is:
    : pcplist cache --> buddy (batch >> order) allocation migratetype
    : freelist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
    : migratetype freelist.
    :
    : Due to the fact that requesting pages from the pcplist cache is faster
    : than buddy, the sequence of modifying the ALLOC_HIGHATOMIC allocation is:
    : pcplist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
    : migrate freelist.
    :
    : This patch can solve the allocation failure of the Non-ALLOC_HIGHATOMIC
    : alloc_flag due to excessive pages reservations in MIGRATE_HIGHATOMIC
    : freelists.

    > --- a/mm/internal.h
    > +++ b/mm/internal.h
    > @@ -905,7 +905,6 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
    > #endif
    > #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */
    > #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
    > -#define ALLOC_PCPLIST 0x1000 /* Allocations from pcplist */
    >
    > /* Flags that allow allocations below the min watermark. */
    > #define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
    > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    > index 67cec88164b1..3c84c3e3eeb0 100755
    > --- a/mm/page_alloc.c
    > +++ b/mm/page_alloc.c
    > @@ -2854,6 +2854,11 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
    > int batch = nr_pcp_alloc(pcp, zone, order);
    > int alloced;
    >
    > + /*
    > + * If pcplist is empty and alloc_flags is with ALLOC_HIGHATOMIC,
    > + * it should alloc from buddy highatomic migrate freelist firstly
    > + * to ensure quick and successful allocation.
    > + */
    > if (alloc_flags & ALLOC_HIGHATOMIC)
    > goto out;
    >
    > @@ -2925,8 +2930,8 @@ __no_sanitize_memory
    > static inline
    > struct page *rmqueue(struct zone *preferred_zone,
    > struct zone *zone, unsigned int order,
    > - gfp_t gfp_flags, unsigned int *alloc_flags,
    > - int migratetype)
    > + gfp_t gfp_flags, unsigned int alloc_flags,
    > + int migratetype, bool *highatomc_allocation)
    > {
    > struct page *page;
    >
    > @@ -2938,19 +2943,33 @@ struct page *rmqueue(struct zone *preferred_zone,
    >
    > if (likely(pcp_allowed_order(order))) {
    > page = rmqueue_pcplist(preferred_zone, zone, order,
    > - migratetype, *alloc_flags);
    > - if (likely(page)) {
    > - *alloc_flags |= ALLOC_PCPLIST;
    > + migratetype, alloc_flags);
    > + if (likely(page))
    > goto out;
    > - }
    > }
    >
    > - page = rmqueue_buddy(preferred_zone, zone, order, *alloc_flags,
    > + page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
    > migratetype);
    >
    > + /*
    > + * The high-order atomic allocation pageblock reserved conditions:
    > + *
    > + * If the high-order atomic allocation page is alloced from pcplist,
    > + * the highatomic pageblock does not need to be reserved, which can
    > + * void to migrate an increasing number of pages into buddy
    > + * MIGRATE_HIGHATOMIC freelist and lead to an increasing risk of
    > + * allocation failure on other buddy migrate freelists.
    > + *
    > + * If the high-order atomic allocation page is alloced from buddy
    > + * highatomic migrate freelist, regardless of whether the allocation
    > + * is successful or not, the highatomic pageblock can try to be
    > + * reserved.
    > + */
    > + if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
    > + *highatomc_allocation = true;
    > out:
    > /* Separate test+clear to avoid unnecessary atomics */
    > - if ((*alloc_flags & ALLOC_KSWAPD) &&
    > + if ((alloc_flags & ALLOC_KSWAPD) &&
    > unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
    > clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
    > wakeup_kswapd(zone, 0, 0, zone_idx(zone));
    > @@ -3218,6 +3237,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
    > struct pglist_data *last_pgdat = NULL;
    > bool last_pgdat_dirty_ok = false;
    > bool no_fallback;
    > + bool highatomc_allocation = false;
    >
    > retry:
    > /*
    > @@ -3349,7 +3369,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
    >
    > try_this_zone:
    > page = rmqueue(ac->preferred_zoneref->zone, zone, order,
    > - gfp_mask, &alloc_flags, ac->migratetype);
    > + gfp_mask, alloc_flags, ac->migratetype, &highatomc_allocation);
    > if (page) {
    > prep_new_page(page, order, gfp_mask, alloc_flags);
    >
    > @@ -3357,8 +3377,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
    > * If this is a high-order atomic allocation then check
    > * if the pageblock should be reserved for the future
    > */
    > - if (unlikely(alloc_flags & ALLOC_HIGHATOMIC) &&
    > - unlikely(!(alloc_flags & ALLOC_PCPLIST)))
    > + if (unlikely(highatomc_allocation))
    > reserve_highatomic_pageblock(page, zone);
    >
    > return page;
    > --
    > 2.39.0

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