.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};
+static DEFINE_SPINLOCK(split_queue_lock);
+static LIST_HEAD(split_queue);
+static unsigned long split_queue_len;
+static struct shrinker deferred_split_shrinker;
static void set_recommended_min_free_kbytes(void)
{
err = register_shrinker(&huge_zero_page_shrinker);
if (err)
goto err_hzp_shrinker;
+ err = register_shrinker(&deferred_split_shrinker);
+ if (err)
+ goto err_split_shrinker;
/*
* By default disable transparent hugepages on smaller systems,
return 0;
err_khugepaged:
+ unregister_shrinker(&deferred_split_shrinker);
+err_split_shrinker:
unregister_shrinker(&huge_zero_page_shrinker);
err_hzp_shrinker:
khugepaged_slab_exit();
return entry;
}
+static inline struct list_head *page_deferred_list(struct page *page)
+{
+ /*
+ * ->lru in the tail pages is occupied by compound_head.
+ * Let's use ->mapping + ->index in the second tail page as list_head.
+ */
+ return (struct list_head *)&page[2].mapping;
+}
+
+void prep_transhuge_page(struct page *page)
+{
+ /*
+ * we use page->mapping and page->indexlru in second tail page
+ * as list_head: assuming THP order >= 2
+ */
+ BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
+
+ INIT_LIST_HEAD(page_deferred_list(page));
+ set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
+}
+
static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
+ prep_transhuge_page(page);
return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
flags);
}
} else
new_page = NULL;
- if (unlikely(!new_page)) {
+ if (likely(new_page)) {
+ prep_transhuge_page(new_page);
+ } else {
if (!page) {
split_huge_pmd(vma, pmd, address);
ret |= VM_FAULT_FALLBACK;
return NULL;
}
+ prep_transhuge_page(*hpage);
count_vm_event(THP_COLLAPSE_ALLOC);
return *hpage;
}
static inline struct page *alloc_hugepage(int defrag)
{
- return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
- HPAGE_PMD_ORDER);
+ struct page *page;
+
+ page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER);
+ if (page)
+ prep_transhuge_page(page);
+ return page;
}
static struct page *khugepaged_alloc_hugepage(bool *wait)
set_page_idle(page_tail);
/* ->mapping in first tail page is compound_mapcount */
- VM_BUG_ON_PAGE(tail != 1 && page_tail->mapping != TAIL_MAPPING,
+ VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
page_tail);
page_tail->mapping = head->mapping;
freeze_page(anon_vma, head);
VM_BUG_ON_PAGE(compound_mapcount(head), head);
+ /* Prevent deferred_split_scan() touching ->_count */
+ spin_lock(&split_queue_lock);
count = page_count(head);
mapcount = total_mapcount(head);
if (mapcount == count - 1) {
+ if (!list_empty(page_deferred_list(head))) {
+ split_queue_len--;
+ list_del(page_deferred_list(head));
+ }
+ spin_unlock(&split_queue_lock);
__split_huge_page(page, list);
ret = 0;
} else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount > count - 1) {
+ spin_unlock(&split_queue_lock);
pr_alert("total_mapcount: %u, page_count(): %u\n",
mapcount, count);
if (PageTail(page))
dump_page(page, "total_mapcount(head) > page_count(head) - 1");
BUG();
} else {
+ spin_unlock(&split_queue_lock);
unfreeze_page(anon_vma, head);
ret = -EBUSY;
}
count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
return ret;
}
+
+void free_transhuge_page(struct page *page)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&split_queue_lock, flags);
+ if (!list_empty(page_deferred_list(page))) {
+ split_queue_len--;
+ list_del(page_deferred_list(page));
+ }
+ spin_unlock_irqrestore(&split_queue_lock, flags);
+ free_compound_page(page);
+}
+
+void deferred_split_huge_page(struct page *page)
+{
+ unsigned long flags;
+
+ VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+
+ spin_lock_irqsave(&split_queue_lock, flags);
+ if (list_empty(page_deferred_list(page))) {
+ list_add_tail(page_deferred_list(page), &split_queue);
+ split_queue_len++;
+ }
+ spin_unlock_irqrestore(&split_queue_lock, flags);
+}
+
+static unsigned long deferred_split_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ /*
+ * Split a page from split_queue will free up at least one page,
+ * at most HPAGE_PMD_NR - 1. We don't track exact number.
+ * Let's use HPAGE_PMD_NR / 2 as ballpark.
+ */
+ return ACCESS_ONCE(split_queue_len) * HPAGE_PMD_NR / 2;
+}
+
+static unsigned long deferred_split_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ unsigned long flags;
+ LIST_HEAD(list), *pos, *next;
+ struct page *page;
+ int split = 0;
+
+ spin_lock_irqsave(&split_queue_lock, flags);
+ list_splice_init(&split_queue, &list);
+
+ /* Take pin on all head pages to avoid freeing them under us */
+ list_for_each_safe(pos, next, &list) {
+ page = list_entry((void *)pos, struct page, mapping);
+ page = compound_head(page);
+ /* race with put_compound_page() */
+ if (!get_page_unless_zero(page)) {
+ list_del_init(page_deferred_list(page));
+ split_queue_len--;
+ }
+ }
+ spin_unlock_irqrestore(&split_queue_lock, flags);
+
+ list_for_each_safe(pos, next, &list) {
+ page = list_entry((void *)pos, struct page, mapping);
+ lock_page(page);
+ /* split_huge_page() removes page from list on success */
+ if (!split_huge_page(page))
+ split++;
+ unlock_page(page);
+ put_page(page);
+ }
+
+ spin_lock_irqsave(&split_queue_lock, flags);
+ list_splice_tail(&list, &split_queue);
+ spin_unlock_irqrestore(&split_queue_lock, flags);
+
+ return split * HPAGE_PMD_NR / 2;
+}
+
+static struct shrinker deferred_split_shrinker = {
+ .count_objects = deferred_split_count,
+ .scan_objects = deferred_split_scan,
+ .seeks = DEFAULT_SEEKS,
+};
#endif
};
-static void free_compound_page(struct page *page);
compound_page_dtor * const compound_page_dtors[] = {
NULL,
free_compound_page,
#ifdef CONFIG_HUGETLB_PAGE
free_huge_page,
#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ free_transhuge_page,
+#endif
};
int min_free_kbytes = 1024;
* This usage means that zero-order pages may not be compound.
*/
-static void free_compound_page(struct page *page)
+void free_compound_page(struct page *page)
{
__free_pages_ok(page, compound_order(page));
}
ret = 0;
goto out;
}
- /* mapping in first tail page is used for compound_mapcount() */
- if (page - head_page == 1) {
+ switch (page - head_page) {
+ case 1:
+ /* the first tail page: ->mapping is compound_mapcount() */
if (unlikely(compound_mapcount(page))) {
bad_page(page, "nonzero compound_mapcount", 0);
goto out;
}
- } else if (page->mapping != TAIL_MAPPING) {
- bad_page(page, "corrupted mapping in tail page", 0);
- goto out;
+ break;
+ case 2:
+ /*
+ * the second tail page: ->mapping is
+ * page_deferred_list().next -- ignore value.
+ */
+ break;
+ default:
+ if (page->mapping != TAIL_MAPPING) {
+ bad_page(page, "corrupted mapping in tail page", 0);
+ goto out;
+ }
+ break;
}
if (unlikely(!PageTail(page))) {
bad_page(page, "PageTail not set", 0);
projects / users / hch / configfs.git / commitdiff