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[RFCv2 1/6] mm: introduce MADV_COLD




When a process expects no accesses to a certain memory range, it could
give a hint to kernel that the pages can be reclaimed when memory pressure
happens but data should be preserved for future use.  This could reduce
workingset eviction so it ends up increasing performance.

This patch introduces the new MADV_COLD hint to madvise(2) syscall.
MADV_COLD can be used by a process to mark a memory range as not expected
to be used in the near future. The hint can help kernel in deciding which
pages to evict early during memory pressure.

Internally, it works via deactivating pages from active list to inactive's
head if the page is private because inactive list could be full of
used-once pages which are first candidate for the reclaiming and that's a
reason why MADV_FREE move pages to head of inactive LRU list. Therefore,
if the memory pressure happens, they will be reclaimed earlier than other
active pages unless there is no access until the time.

* RFCv1
 * renaming from MADV_COOL to MADV_COLD - hannes

* internal review
 * use clear_page_youn in deactivate_page - joelaf
 * Revise the description - surenb
 * Renaming from MADV_WARM to MADV_COOL - surenb

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 include/linux/page-flags.h             |   1 +
 include/linux/page_idle.h              |  15 ++++
 include/linux/swap.h                   |   1 +
 include/uapi/asm-generic/mman-common.h |   1 +
 mm/madvise.c                           | 111 +++++++++++++++++++++++++
 mm/swap.c                              |  43 ++++++++++
 6 files changed, 172 insertions(+)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9f8712a4b1a5..58b06654c8dd 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -424,6 +424,7 @@ static inline bool set_hwpoison_free_buddy_page(struct page *page)
 TESTPAGEFLAG(Young, young, PF_ANY)
 SETPAGEFLAG(Young, young, PF_ANY)
 TESTCLEARFLAG(Young, young, PF_ANY)
+CLEARPAGEFLAG(Young, young, PF_ANY)
 PAGEFLAG(Idle, idle, PF_ANY)
 #endif
 
diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h
index 1e894d34bdce..f3f43b317150 100644
--- a/include/linux/page_idle.h
+++ b/include/linux/page_idle.h
@@ -19,6 +19,11 @@ static inline void set_page_young(struct page *page)
 	SetPageYoung(page);
 }
 
+static inline void clear_page_young(struct page *page)
+{
+	ClearPageYoung(page);
+}
+
 static inline bool test_and_clear_page_young(struct page *page)
 {
 	return TestClearPageYoung(page);
@@ -65,6 +70,16 @@ static inline void set_page_young(struct page *page)
 	set_bit(PAGE_EXT_YOUNG, &page_ext->flags);
 }
 
+static void clear_page_young(struct page *page)
+{
+	struct page_ext *page_ext = lookup_page_ext(page);
+
+	if (unlikely(!page_ext))
+		return;
+
+	clear_bit(PAGE_EXT_YOUNG, &page_ext->flags);
+}
+
 static inline bool test_and_clear_page_young(struct page *page)
 {
 	struct page_ext *page_ext = lookup_page_ext(page);
diff --git a/include/linux/swap.h b/include/linux/swap.h
index de2c67a33b7e..0ce997edb8bb 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -340,6 +340,7 @@ extern void lru_add_drain_cpu(int cpu);
 extern void lru_add_drain_all(void);
 extern void rotate_reclaimable_page(struct page *page);
 extern void deactivate_file_page(struct page *page);
+extern void deactivate_page(struct page *page);
 extern void mark_page_lazyfree(struct page *page);
 extern void swap_setup(void);
 
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index bea0278f65ab..1190f4e7f7b9 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h
@@ -43,6 +43,7 @@
 #define MADV_SEQUENTIAL	2		/* expect sequential page references */
 #define MADV_WILLNEED	3		/* will need these pages */
 #define MADV_DONTNEED	4		/* don't need these pages */
+#define MADV_COLD	5		/* deactivatie these pages */
 
 /* common parameters: try to keep these consistent across architectures */
 #define MADV_FREE	8		/* free pages only if memory pressure */
diff --git a/mm/madvise.c b/mm/madvise.c
index 628022e674a7..bff150eab6da 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -40,6 +40,7 @@ static int madvise_need_mmap_write(int behavior)
 	case MADV_REMOVE:
 	case MADV_WILLNEED:
 	case MADV_DONTNEED:
+	case MADV_COLD:
 	case MADV_FREE:
 		return 0;
 	default:
@@ -307,6 +308,113 @@ static long madvise_willneed(struct vm_area_struct *vma,
 	return 0;
 }
 
+static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
+				unsigned long end, struct mm_walk *walk)
+{
+	pte_t *orig_pte, *pte, ptent;
+	spinlock_t *ptl;
+	struct page *page;
+	struct vm_area_struct *vma = walk->vma;
+	unsigned long next;
+
+	next = pmd_addr_end(addr, end);
+	if (pmd_trans_huge(*pmd)) {
+		ptl = pmd_trans_huge_lock(pmd, vma);
+		if (!ptl)
+			return 0;
+
+		if (is_huge_zero_pmd(*pmd))
+			goto huge_unlock;
+
+		page = pmd_page(*pmd);
+		if (page_mapcount(page) > 1)
+			goto huge_unlock;
+
+		if (next - addr != HPAGE_PMD_SIZE) {
+			int err;
+
+			get_page(page);
+			spin_unlock(ptl);
+			lock_page(page);
+			err = split_huge_page(page);
+			unlock_page(page);
+			put_page(page);
+			if (!err)
+				goto regular_page;
+			return 0;
+		}
+
+		pmdp_test_and_clear_young(vma, addr, pmd);
+		deactivate_page(page);
+huge_unlock:
+		spin_unlock(ptl);
+		return 0;
+	}
+
+	if (pmd_trans_unstable(pmd))
+		return 0;
+
+regular_page:
+	orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+	for (pte = orig_pte; addr < end; pte++, addr += PAGE_SIZE) {
+		ptent = *pte;
+
+		if (pte_none(ptent))
+			continue;
+
+		if (!pte_present(ptent))
+			continue;
+
+		page = vm_normal_page(vma, addr, ptent);
+		if (!page)
+			continue;
+
+		if (page_mapcount(page) > 1)
+			continue;
+
+		ptep_test_and_clear_young(vma, addr, pte);
+		deactivate_page(page);
+	}
+
+	pte_unmap_unlock(orig_pte, ptl);
+	cond_resched();
+
+	return 0;
+}
+
+static void madvise_cold_page_range(struct mmu_gather *tlb,
+			     struct vm_area_struct *vma,
+			     unsigned long addr, unsigned long end)
+{
+	struct mm_walk cool_walk = {
+		.pmd_entry = madvise_cold_pte_range,
+		.mm = vma->vm_mm,
+	};
+
+	tlb_start_vma(tlb, vma);
+	walk_page_range(addr, end, &cool_walk);
+	tlb_end_vma(tlb, vma);
+}
+
+static long madvise_cold(struct vm_area_struct *vma,
+			struct vm_area_struct **prev,
+			unsigned long start_addr, unsigned long end_addr)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct mmu_gather tlb;
+
+	*prev = vma;
+	if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
+		return -EINVAL;
+
+	lru_add_drain();
+	tlb_gather_mmu(&tlb, mm, start_addr, end_addr);
+	madvise_cold_page_range(&tlb, vma, start_addr, end_addr);
+	tlb_finish_mmu(&tlb, start_addr, end_addr);
+
+	return 0;
+}
+
 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 				unsigned long end, struct mm_walk *walk)
 
@@ -695,6 +803,8 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 		return madvise_remove(vma, prev, start, end);
 	case MADV_WILLNEED:
 		return madvise_willneed(vma, prev, start, end);
+	case MADV_COLD:
+		return madvise_cold(vma, prev, start, end);
 	case MADV_FREE:
 	case MADV_DONTNEED:
 		return madvise_dontneed_free(vma, prev, start, end, behavior);
@@ -716,6 +826,7 @@ madvise_behavior_valid(int behavior)
 	case MADV_WILLNEED:
 	case MADV_DONTNEED:
 	case MADV_FREE:
+	case MADV_COLD:
 #ifdef CONFIG_KSM
 	case MADV_MERGEABLE:
 	case MADV_UNMERGEABLE:
diff --git a/mm/swap.c b/mm/swap.c
index 7b079976cbec..cebedab15aa2 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -47,6 +47,7 @@ int page_cluster;
 static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_file_pvecs);
+static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
 static DEFINE_PER_CPU(struct pagevec, lru_lazyfree_pvecs);
 #ifdef CONFIG_SMP
 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
@@ -538,6 +539,23 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
 	update_page_reclaim_stat(lruvec, file, 0);
 }
 
+static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
+			    void *arg)
+{
+	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
+		int file = page_is_file_cache(page);
+		int lru = page_lru_base_type(page);
+
+		del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
+		ClearPageActive(page);
+		ClearPageReferenced(page);
+		clear_page_young(page);
+		add_page_to_lru_list(page, lruvec, lru);
+
+		__count_vm_events(PGDEACTIVATE, hpage_nr_pages(page));
+		update_page_reclaim_stat(lruvec, file, 0);
+	}
+}
 
 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
 			    void *arg)
@@ -590,6 +608,10 @@ void lru_add_drain_cpu(int cpu)
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
 
+	pvec = &per_cpu(lru_deactivate_pvecs, cpu);
+	if (pagevec_count(pvec))
+		pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
+
 	pvec = &per_cpu(lru_lazyfree_pvecs, cpu);
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
@@ -623,6 +645,26 @@ void deactivate_file_page(struct page *page)
 	}
 }
 
+/*
+ * deactivate_page - deactivate a page
+ * @page: page to deactivate
+ *
+ * deactivate_page() moves @page to the inactive list if @page was on the active
+ * list and was not an unevictable page.  This is done to accelerate the reclaim
+ * of @page.
+ */
+void deactivate_page(struct page *page)
+{
+	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
+		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
+
+		get_page(page);
+		if (!pagevec_add(pvec, page) || PageCompound(page))
+			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
+		put_cpu_var(lru_deactivate_pvecs);
+	}
+}
+
 /**
  * mark_page_lazyfree - make an anon page lazyfree
  * @page: page to deactivate
@@ -687,6 +729,7 @@ void lru_add_drain_all(void)
 		if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
 		    pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
 		    pagevec_count(&per_cpu(lru_deactivate_file_pvecs, cpu)) ||
+		    pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
 		    pagevec_count(&per_cpu(lru_lazyfree_pvecs, cpu)) ||
 		    need_activate_page_drain(cpu)) {
 			INIT_WORK(work, lru_add_drain_per_cpu);
-- 
2.22.0.rc1.257.g3120a18244-goog