Re: Fwd: Control page reclaim granularity

[Zheng Liu]

This only a first trivial try.  If this flag is set, reclaimer just give this
page one more round trip rather than promote it into active list.  Any comments
or advices are welcomed.

Regards,
Zheng

[PATCH] mm: per-inode mmaped page reclaim

From: Zheng Liu <wenqing.lz@xxxxxxxxxx>

In some cases, user wants to control mmaped page reclaim granularity.  A new
flag is added into struct address_space to give the page one more round trip.
AS_WORKINGSET flag cannot be added in vma->vm_flags because this flag has no
room for a new flag in 32 bit.  Now user can call madvise(2) to set this flag
for a file.  If this flag is set, all pages will be given one more round trip
when reclaimer tries to shrink pages.

Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
---
 include/asm-generic/mman-common.h |    2 ++
 include/linux/pagemap.h           |   16 ++++++++++++++++
 mm/madvise.c                      |    8 ++++++++
 mm/vmscan.c                       |   15 +++++++++++++++
 4 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/include/asm-generic/mman-common.h b/include/asm-generic/mman-common.h
index 787abbb..7d26c9b 100644
--- a/include/asm-generic/mman-common.h
+++ b/include/asm-generic/mman-common.h
@@ -48,6 +48,8 @@
 #define MADV_HUGEPAGE	14		/* Worth backing with hugepages */
 #define MADV_NOHUGEPAGE	15		/* Not worth backing with hugepages */
 
+#define MADV_WORKINGSET 16		/* give one more round trip */
+
 /* compatibility flags */
 #define MAP_FILE	0
 
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index cfaaa69..80532a0 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -24,6 +24,7 @@ enum mapping_flags {
 	AS_ENOSPC	= __GFP_BITS_SHIFT + 1,	/* ENOSPC on async write */
 	AS_MM_ALL_LOCKS	= __GFP_BITS_SHIFT + 2,	/* under mm_take_all_locks() */
 	AS_UNEVICTABLE	= __GFP_BITS_SHIFT + 3,	/* e.g., ramdisk, SHM_LOCK */
+	AS_WORKINGSET	= __GFP_BITS_SHIFT + 4, /* give one more round trip */
 };
 
 static inline void mapping_set_error(struct address_space *mapping, int error)
@@ -36,6 +37,21 @@ static inline void mapping_set_error(struct address_space *mapping, int error)
 	}
 }
 
+static inline void mapping_set_workingset(struct address_space *mapping)
+{
+	set_bit(AS_WORKINGSET, &mapping->flags);
+}
+
+static inline void mapping_clear_workingset(struct address_space *mapping)
+{
+	clear_bit(AS_WORKINGSET, &mapping->flags);
+}
+
+static inline int mapping_test_workingset(struct address_space *mapping)
+{
+	return mapping && test_bit(AS_WORKINGSET, &mapping->flags);
+}
+
 static inline void mapping_set_unevictable(struct address_space *mapping)
 {
 	set_bit(AS_UNEVICTABLE, &mapping->flags);
diff --git a/mm/madvise.c b/mm/madvise.c
index 74bf193..8ca6c9b 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -77,6 +77,14 @@ static long madvise_behavior(struct vm_area_struct * vma,
 		if (error)
 			goto out;
 		break;
+	case MADV_WORKINGSET:
+		if (vma->vm_file && vma->vm_file->f_mapping) {
+			mapping_set_workingset(vma->vm_file->f_mapping);
+		} else {
+			error = -EPERM;
+			goto out;
+		}
+		break;
 	}
 
 	if (new_flags == vma->vm_flags) {
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c52b235..51f745b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -721,6 +721,15 @@ static enum page_references page_check_references(struct page *page,
 	if (vm_flags & VM_LOCKED)
 		return PAGEREF_RECLAIM;
 
+	/*
+	 * give this page one more round trip because workingset
+	 * flag is set.
+	 */
+	if (mapping_test_workingset(page_mapping(page))) {
+		mapping_clear_workingset(page_mapping(page));
+		return PAGEREF_KEEP;
+	}
+
 	if (referenced_ptes) {
 		if (PageAnon(page))
 			return PAGEREF_ACTIVATE;
@@ -1737,6 +1746,12 @@ static void shrink_active_list(unsigned long nr_to_scan,
 			continue;
 		}
 
+		if (mapping_test_workingset(page_mapping(page))) {
+			mapping_clear_workingset(page_mapping(page));
+			list_add(&page->lru, &l_active);
+			continue;
+		}
+
 		if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
 			nr_rotated += hpage_nr_pages(page);
 			/*
-- 
1.7.4.1

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