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Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > __free_pages_core() is used when exposing fresh memory to the buddy > during system boot and when onlining memory in generic_online_page(). > > generic_online_page() is used in two cases: > > 1. Direct memory onlining in online_pages(). > 2. Deferred memory onlining in memory-ballooning-like mechanisms (HyperV > balloon and virtio-mem), when parts of a section are kept > fake-offline to be fake-onlined later on. > > In 1, we already place pages to the tail of the freelist. Pages will be > freed to MIGRATE_ISOLATE lists first and moved to the tail of the freelists > via undo_isolate_page_range(). > > In 2, we currently don't implement a proper rule. In case of virtio-mem, > where we currently always online MAX_ORDER - 1 pages, the pages will be > placed to the HEAD of the freelist - undesireable. While the hyper-v > balloon calls generic_online_page() with single pages, usually it will > call it on successive single pages in a larger block. > > The pages are fresh, so place them to the tail of the freelists and avoid > the PCP. In __free_pages_core(), remove the now superflouos call to > set_page_refcounted() and add a comment regarding page initialization and > the refcount. > > Note: In 2. we currently don't shuffle. If ever relevant (page shuffling > is usually of limited use in virtualized environments), we might want to > shuffle after a sequence of generic_online_page() calls in the > relevant callers. > > Reviewed-by: Vlastimil Babka > Reviewed-by: Oscar Salvador > Cc: Andrew Morton > Cc: Alexander Duyck > Cc: Mel Gorman > Cc: Michal Hocko > Cc: Dave Hansen > Cc: Vlastimil Babka > Cc: Wei Yang > Cc: Oscar Salvador > Cc: Mike Rapoport > Cc: "K. Y. Srinivasan" > Cc: Haiyang Zhang > Cc: Stephen Hemminger > Cc: Wei Liu > Signed-off-by: David Hildenbrand > --- > mm/page_alloc.c | 37 ++++++++++++++++++++++++------------- > 1 file changed, 24 insertions(+), 13 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d5a5f528b8ca..8a2134fe9947 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -270,7 +270,8 @@ bool pm_suspended_storage(void) > unsigned int pageblock_order __read_mostly; > #endif > > -static void __free_pages_ok(struct page *page, unsigned int order); > +static void __free_pages_ok(struct page *page, unsigned int order, > + fop_t fop_flags); > > /* > * results with 256, 32 in the lowmem_reserve sysctl: > @@ -682,7 +683,7 @@ static void bad_page(struct page *page, const char *reason) > void free_compound_page(struct page *page) > { > mem_cgroup_uncharge(page); > - __free_pages_ok(page, compound_order(page)); > + __free_pages_ok(page, compound_order(page), FOP_NONE); > } > > void prep_compound_page(struct page *page, unsigned int order) > @@ -1419,17 +1420,15 @@ static void free_pcppages_bulk(struct zone *zone, int count, > spin_unlock(&zone->lock); > } > > -static void free_one_page(struct zone *zone, > - struct page *page, unsigned long pfn, > - unsigned int order, > - int migratetype) > +static void free_one_page(struct zone *zone, struct page *page, unsigned long pfn, > + unsigned int order, int migratetype, fop_t fop_flags) > { > spin_lock(&zone->lock); > if (unlikely(has_isolate_pageblock(zone) || > is_migrate_isolate(migratetype))) { > migratetype = get_pfnblock_migratetype(page, pfn); > } > - __free_one_page(page, pfn, zone, order, migratetype, FOP_NONE); > + __free_one_page(page, pfn, zone, order, migratetype, fop_flags); > spin_unlock(&zone->lock); > } > > @@ -1507,7 +1506,8 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end) > } > } > > -static void __free_pages_ok(struct page *page, unsigned int order) > +static void __free_pages_ok(struct page *page, unsigned int order, > + fop_t fop_flags) > { > unsigned long flags; > int migratetype; > @@ -1519,7 +1519,8 @@ static void __free_pages_ok(struct page *page, unsigned int order) > migratetype = get_pfnblock_migratetype(page, pfn); > local_irq_save(flags); > __count_vm_events(PGFREE, 1 << order); > - free_one_page(page_zone(page), page, pfn, order, migratetype); > + free_one_page(page_zone(page), page, pfn, order, migratetype, > + fop_flags); > local_irq_restore(flags); > } > > @@ -1529,6 +1530,11 @@ void __free_pages_core(struct page *page, unsigned int order) > struct page *p = page; > unsigned int loop; > > + /* > + * When initializing the memmap, init_single_page() sets the refcount > + * of all pages to 1 ("allocated"/"not free"). We have to set the > + * refcount of all involved pages to 0. > + */ > prefetchw(p); > for (loop = 0; loop < (nr_pages - 1); loop++, p++) { > prefetchw(p + 1); > @@ -1539,8 +1545,12 @@ void __free_pages_core(struct page *page, unsigned int order) > set_page_count(p, 0); > > atomic_long_add(nr_pages, &page_zone(page)->managed_pages); > - set_page_refcounted(page); > - __free_pages(page, order); > + > + /* > + * Bypass PCP and place fresh pages right to the tail, primarily > + * relevant for memory onlining. > + */ > + __free_pages_ok(page, order, FOP_TO_TAIL); > } > > #ifdef CONFIG_NEED_MULTIPLE_NODES > @@ -3171,7 +3181,8 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn) > */ > if (migratetype >= MIGRATE_PCPTYPES) { > if (unlikely(is_migrate_isolate(migratetype))) { > - free_one_page(zone, page, pfn, 0, migratetype); > + free_one_page(zone, page, pfn, 0, migratetype, > + FOP_NONE); > return; > } > migratetype = MIGRATE_MOVABLE; > @@ -5063,7 +5074,7 @@ static inline void free_the_page(struct page *page, unsigned int order) > if (order == 0) /* Via pcp? */ > free_unref_page(page); > else > - __free_pages_ok(page, order); > + __free_pages_ok(page, order, FOP_NONE); > } > > void __free_pages(struct page *page, unsigned int order) Acked-by: Pankaj Gupta