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mm: pack compound_dtor and compound_order into one word in struct page
The patch halves space occupied by compound_dtor and compound_order in struct page. For compound_order, it's trivial long -> short conversion. For get_compound_page_dtor(), we now use hardcoded table for destructor lookup and store its index in the struct page instead of direct pointer to destructor. It shouldn't be a big trouble to maintain the table: we have only two destructor and NULL currently. This patch free up one word in tail pages for reuse. This is preparation for the next patch. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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32e7ba1ea1
commit
f1e61557f0
4 changed files with 35 additions and 14 deletions
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@ -568,18 +568,32 @@ int split_free_page(struct page *page);
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/*
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* Compound pages have a destructor function. Provide a
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* prototype for that function and accessor functions.
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* These are _only_ valid on the head of a PG_compound page.
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* These are _only_ valid on the head of a compound page.
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*/
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typedef void compound_page_dtor(struct page *);
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/* Keep the enum in sync with compound_page_dtors array in mm/page_alloc.c */
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enum compound_dtor_id {
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NULL_COMPOUND_DTOR,
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COMPOUND_PAGE_DTOR,
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#ifdef CONFIG_HUGETLB_PAGE
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HUGETLB_PAGE_DTOR,
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#endif
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NR_COMPOUND_DTORS,
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};
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extern compound_page_dtor * const compound_page_dtors[];
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static inline void set_compound_page_dtor(struct page *page,
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compound_page_dtor *dtor)
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enum compound_dtor_id compound_dtor)
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{
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page[1].compound_dtor = dtor;
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VM_BUG_ON_PAGE(compound_dtor >= NR_COMPOUND_DTORS, page);
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page[1].compound_dtor = compound_dtor;
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}
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static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
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{
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return page[1].compound_dtor;
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VM_BUG_ON_PAGE(page[1].compound_dtor >= NR_COMPOUND_DTORS, page);
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return compound_page_dtors[page[1].compound_dtor];
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}
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static inline int compound_order(struct page *page)
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@ -589,7 +603,7 @@ static inline int compound_order(struct page *page)
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return page[1].compound_order;
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}
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static inline void set_compound_order(struct page *page, unsigned long order)
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static inline void set_compound_order(struct page *page, unsigned int order)
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{
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page[1].compound_order = order;
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}
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@ -28,8 +28,6 @@ struct mem_cgroup;
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IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
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#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
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typedef void compound_page_dtor(struct page *);
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/*
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* Each physical page in the system has a struct page associated with
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* it to keep track of whatever it is we are using the page for at the
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@ -136,8 +134,8 @@ struct page {
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*/
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/* First tail page of compound page */
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struct {
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compound_page_dtor *compound_dtor;
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unsigned long compound_order;
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unsigned short int compound_dtor;
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unsigned short int compound_order;
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};
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#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
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@ -1146,7 +1146,7 @@ static void update_and_free_page(struct hstate *h, struct page *page)
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1 << PG_writeback);
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}
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VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
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set_compound_page_dtor(page, NULL);
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set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
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set_page_refcounted(page);
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if (hstate_is_gigantic(h)) {
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destroy_compound_gigantic_page(page, huge_page_order(h));
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@ -1242,7 +1242,7 @@ void free_huge_page(struct page *page)
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static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
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{
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INIT_LIST_HEAD(&page->lru);
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set_compound_page_dtor(page, free_huge_page);
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set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
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spin_lock(&hugetlb_lock);
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set_hugetlb_cgroup(page, NULL);
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h->nr_huge_pages++;
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@ -1294,7 +1294,7 @@ int PageHuge(struct page *page)
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return 0;
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page = compound_head(page);
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return get_compound_page_dtor(page) == free_huge_page;
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return page[1].compound_dtor == HUGETLB_PAGE_DTOR;
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}
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EXPORT_SYMBOL_GPL(PageHuge);
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@ -1568,7 +1568,7 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
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if (page) {
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INIT_LIST_HEAD(&page->lru);
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r_nid = page_to_nid(page);
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set_compound_page_dtor(page, free_huge_page);
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set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
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set_hugetlb_cgroup(page, NULL);
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/*
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* We incremented the global counters already
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@ -229,6 +229,15 @@ static char * const zone_names[MAX_NR_ZONES] = {
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#endif
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};
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static void free_compound_page(struct page *page);
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compound_page_dtor * const compound_page_dtors[] = {
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NULL,
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free_compound_page,
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#ifdef CONFIG_HUGETLB_PAGE
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free_huge_page,
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#endif
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};
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int min_free_kbytes = 1024;
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int user_min_free_kbytes = -1;
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@ -458,7 +467,7 @@ void prep_compound_page(struct page *page, unsigned long order)
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int i;
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int nr_pages = 1 << order;
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set_compound_page_dtor(page, free_compound_page);
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set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
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set_compound_order(page, order);
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__SetPageHead(page);
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for (i = 1; i < nr_pages; i++) {
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