Re: [ 06/73] mm: compaction: introduce sync-light migration for use by compaction

[Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>]

On Tue, Jul 31, 2012 at 05:43:16AM +0100, Ben Hutchings wrote:
> 3.2-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Mel Gorman <mgorman@suse.de>
> 
> commit a6bc32b899223a877f595ef9ddc1e89ead5072b8 upstream.

We need also to pick recent fix dc32f63453f56d07a1073a697dcd843dd3098c09 after
applying this one.

> 
> Stable note: Not tracked in Buzilla. This was part of a series that
> 	reduced interactivity stalls experienced when THP was enabled.
> 	These stalls were particularly noticable when copying data
> 	to a USB stick but the experiences for users varied a lot.
> 
> This patch adds a lightweight sync migrate operation MIGRATE_SYNC_LIGHT
> mode that avoids writing back pages to backing storage.  Async compaction
> maps to MIGRATE_ASYNC while sync compaction maps to MIGRATE_SYNC_LIGHT.
> For other migrate_pages users such as memory hotplug, MIGRATE_SYNC is
> used.
> 
> This avoids sync compaction stalling for an excessive length of time,
> particularly when copying files to a USB stick where there might be a
> large number of dirty pages backed by a filesystem that does not support
> ->writepages.
> 
> [aarcange@redhat.com: This patch is heavily based on Andrea's work]
> [akpm@linux-foundation.org: fix fs/nfs/write.c build]
> [akpm@linux-foundation.org: fix fs/btrfs/disk-io.c build]
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Reviewed-by: Rik van Riel <riel@redhat.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Minchan Kim <minchan.kim@gmail.com>
> Cc: Dave Jones <davej@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Andy Isaacson <adi@hexapodia.org>
> Cc: Nai Xia <nai.xia@gmail.com>
> Cc: Johannes Weiner <jweiner@redhat.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  fs/btrfs/disk-io.c      |    5 +--
>  fs/hugetlbfs/inode.c    |    2 +-
>  fs/nfs/internal.h       |    2 +-
>  fs/nfs/write.c          |    4 +--
>  include/linux/fs.h      |    6 ++--
>  include/linux/migrate.h |   23 +++++++++++---
>  mm/compaction.c         |    2 +-
>  mm/memory-failure.c     |    2 +-
>  mm/memory_hotplug.c     |    2 +-
>  mm/mempolicy.c          |    2 +-
>  mm/migrate.c            |   78 ++++++++++++++++++++++++++---------------------
>  11 files changed, 76 insertions(+), 52 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 1375494..d852566 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -872,7 +872,8 @@ static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
>  
>  #ifdef CONFIG_MIGRATION
>  static int btree_migratepage(struct address_space *mapping,
> -			struct page *newpage, struct page *page, bool sync)
> +			struct page *newpage, struct page *page,
> +			enum migrate_mode mode)
>  {
>  	/*
>  	 * we can't safely write a btree page from here,
> @@ -887,7 +888,7 @@ static int btree_migratepage(struct address_space *mapping,
>  	if (page_has_private(page) &&
>  	    !try_to_release_page(page, GFP_KERNEL))
>  		return -EAGAIN;
> -	return migrate_page(mapping, newpage, page, sync);
> +	return migrate_page(mapping, newpage, page, mode);
>  }
>  #endif
>  
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 06fd460..1e85a7a 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -584,7 +584,7 @@ static int hugetlbfs_set_page_dirty(struct page *page)
>  
>  static int hugetlbfs_migrate_page(struct address_space *mapping,
>  				struct page *newpage, struct page *page,
> -				bool sync)
> +				enum migrate_mode mode)
>  {
>  	int rc;
>  
> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> index 114398a..8102db9 100644
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -332,7 +332,7 @@ void nfs_commit_release_pages(struct nfs_write_data *data);
>  
>  #ifdef CONFIG_MIGRATION
>  extern int nfs_migrate_page(struct address_space *,
> -		struct page *, struct page *, bool);
> +		struct page *, struct page *, enum migrate_mode);
>  #else
>  #define nfs_migrate_page NULL
>  #endif
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index 889e98b..834f0fe 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1688,7 +1688,7 @@ out_error:
>  
>  #ifdef CONFIG_MIGRATION
>  int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
> -		struct page *page, bool sync)
> +		struct page *page, enum migrate_mode mode)
>  {
>  	/*
>  	 * If PagePrivate is set, then the page is currently associated with
> @@ -1703,7 +1703,7 @@ int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
>  
>  	nfs_fscache_release_page(page, GFP_KERNEL);
>  
> -	return migrate_page(mapping, newpage, page, sync);
> +	return migrate_page(mapping, newpage, page, mode);
>  }
>  #endif
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b92b73d..e694bd4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -525,6 +525,7 @@ enum positive_aop_returns {
>  struct page;
>  struct address_space;
>  struct writeback_control;
> +enum migrate_mode;
>  
>  struct iov_iter {
>  	const struct iovec *iov;
> @@ -614,7 +615,7 @@ struct address_space_operations {
>  	 * is false, it must not block.
>  	 */
>  	int (*migratepage) (struct address_space *,
> -			struct page *, struct page *, bool);
> +			struct page *, struct page *, enum migrate_mode);
>  	int (*launder_page) (struct page *);
>  	int (*is_partially_uptodate) (struct page *, read_descriptor_t *,
>  					unsigned long);
> @@ -2540,7 +2541,8 @@ extern int generic_check_addressable(unsigned, u64);
>  
>  #ifdef CONFIG_MIGRATION
>  extern int buffer_migrate_page(struct address_space *,
> -				struct page *, struct page *, bool);
> +				struct page *, struct page *,
> +				enum migrate_mode);
>  #else
>  #define buffer_migrate_page NULL
>  #endif
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 14e6d2a..eaf8674 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -6,18 +6,31 @@
>  
>  typedef struct page *new_page_t(struct page *, unsigned long private, int **);
>  
> +/*
> + * MIGRATE_ASYNC means never block
> + * MIGRATE_SYNC_LIGHT in the current implementation means to allow blocking
> + *	on most operations but not ->writepage as the potential stall time
> + *	is too significant
> + * MIGRATE_SYNC will block when migrating pages
> + */
> +enum migrate_mode {
> +	MIGRATE_ASYNC,
> +	MIGRATE_SYNC_LIGHT,
> +	MIGRATE_SYNC,
> +};
> +
>  #ifdef CONFIG_MIGRATION
>  #define PAGE_MIGRATION 1
>  
>  extern void putback_lru_pages(struct list_head *l);
>  extern int migrate_page(struct address_space *,
> -			struct page *, struct page *, bool);
> +			struct page *, struct page *, enum migrate_mode);
>  extern int migrate_pages(struct list_head *l, new_page_t x,
>  			unsigned long private, bool offlining,
> -			bool sync);
> +			enum migrate_mode mode);
>  extern int migrate_huge_pages(struct list_head *l, new_page_t x,
>  			unsigned long private, bool offlining,
> -			bool sync);
> +			enum migrate_mode mode);
>  
>  extern int fail_migrate_page(struct address_space *,
>  			struct page *, struct page *);
> @@ -36,10 +49,10 @@ extern int migrate_huge_page_move_mapping(struct address_space *mapping,
>  static inline void putback_lru_pages(struct list_head *l) {}
>  static inline int migrate_pages(struct list_head *l, new_page_t x,
>  		unsigned long private, bool offlining,
> -		bool sync) { return -ENOSYS; }
> +		enum migrate_mode mode) { return -ENOSYS; }
>  static inline int migrate_huge_pages(struct list_head *l, new_page_t x,
>  		unsigned long private, bool offlining,
> -		bool sync) { return -ENOSYS; }
> +		enum migrate_mode mode) { return -ENOSYS; }
>  
>  static inline int migrate_prep(void) { return -ENOSYS; }
>  static inline int migrate_prep_local(void) { return -ENOSYS; }
> diff --git a/mm/compaction.c b/mm/compaction.c
> index fb29158..71a58f6 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -557,7 +557,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
>  		nr_migrate = cc->nr_migratepages;
>  		err = migrate_pages(&cc->migratepages, compaction_alloc,
>  				(unsigned long)cc, false,
> -				cc->sync);
> +				cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC);
>  		update_nr_listpages(cc);
>  		nr_remaining = cc->nr_migratepages;
>  
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 06d3479..56080ea 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1557,7 +1557,7 @@ int soft_offline_page(struct page *page, int flags)
>  					    page_is_file_cache(page));
>  		list_add(&page->lru, &pagelist);
>  		ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
> -								0, true);
> +							0, MIGRATE_SYNC);
>  		if (ret) {
>  			putback_lru_pages(&pagelist);
>  			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 2168489..6629faf 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -809,7 +809,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
>  		}
>  		/* this function returns # of failed pages */
>  		ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
> -								true, true);
> +							true, MIGRATE_SYNC);
>  		if (ret)
>  			putback_lru_pages(&source);
>  	}
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index e3d58f0..06b145f 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -942,7 +942,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>  
>  	if (!list_empty(&pagelist)) {
>  		err = migrate_pages(&pagelist, new_node_page, dest,
> -								false, true);
> +							false, MIGRATE_SYNC);
>  		if (err)
>  			putback_lru_pages(&pagelist);
>  	}
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 4e86f3b..9871a56 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -218,12 +218,13 @@ out:
>  
>  #ifdef CONFIG_BLOCK
>  /* Returns true if all buffers are successfully locked */
> -static bool buffer_migrate_lock_buffers(struct buffer_head *head, bool sync)
> +static bool buffer_migrate_lock_buffers(struct buffer_head *head,
> +							enum migrate_mode mode)
>  {
>  	struct buffer_head *bh = head;
>  
>  	/* Simple case, sync compaction */
> -	if (sync) {
> +	if (mode != MIGRATE_ASYNC) {
>  		do {
>  			get_bh(bh);
>  			lock_buffer(bh);
> @@ -259,7 +260,7 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head, bool sync)
>  }
>  #else
>  static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
> -								bool sync)
> +							enum migrate_mode mode)
>  {
>  	return true;
>  }
> @@ -275,7 +276,7 @@ static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
>   */
>  static int migrate_page_move_mapping(struct address_space *mapping,
>  		struct page *newpage, struct page *page,
> -		struct buffer_head *head, bool sync)
> +		struct buffer_head *head, enum migrate_mode mode)
>  {
>  	int expected_count;
>  	void **pslot;
> @@ -311,7 +312,8 @@ static int migrate_page_move_mapping(struct address_space *mapping,
>  	 * the mapping back due to an elevated page count, we would have to
>  	 * block waiting on other references to be dropped.
>  	 */
> -	if (!sync && head && !buffer_migrate_lock_buffers(head, sync)) {
> +	if (mode == MIGRATE_ASYNC && head &&
> +			!buffer_migrate_lock_buffers(head, mode)) {
>  		page_unfreeze_refs(page, expected_count);
>  		spin_unlock_irq(&mapping->tree_lock);
>  		return -EAGAIN;
> @@ -472,13 +474,14 @@ EXPORT_SYMBOL(fail_migrate_page);
>   * Pages are locked upon entry and exit.
>   */
>  int migrate_page(struct address_space *mapping,
> -		struct page *newpage, struct page *page, bool sync)
> +		struct page *newpage, struct page *page,
> +		enum migrate_mode mode)
>  {
>  	int rc;
>  
>  	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
>  
> -	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, sync);
> +	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
>  
>  	if (rc)
>  		return rc;
> @@ -495,17 +498,17 @@ EXPORT_SYMBOL(migrate_page);
>   * exist.
>   */
>  int buffer_migrate_page(struct address_space *mapping,
> -		struct page *newpage, struct page *page, bool sync)
> +		struct page *newpage, struct page *page, enum migrate_mode mode)
>  {
>  	struct buffer_head *bh, *head;
>  	int rc;
>  
>  	if (!page_has_buffers(page))
> -		return migrate_page(mapping, newpage, page, sync);
> +		return migrate_page(mapping, newpage, page, mode);
>  
>  	head = page_buffers(page);
>  
> -	rc = migrate_page_move_mapping(mapping, newpage, page, head, sync);
> +	rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
>  
>  	if (rc)
>  		return rc;
> @@ -515,8 +518,8 @@ int buffer_migrate_page(struct address_space *mapping,
>  	 * with an IRQ-safe spinlock held. In the sync case, the buffers
>  	 * need to be locked now
>  	 */
> -	if (sync)
> -		BUG_ON(!buffer_migrate_lock_buffers(head, sync));
> +	if (mode != MIGRATE_ASYNC)
> +		BUG_ON(!buffer_migrate_lock_buffers(head, mode));
>  
>  	ClearPagePrivate(page);
>  	set_page_private(newpage, page_private(page));
> @@ -593,10 +596,11 @@ static int writeout(struct address_space *mapping, struct page *page)
>   * Default handling if a filesystem does not provide a migration function.
>   */
>  static int fallback_migrate_page(struct address_space *mapping,
> -	struct page *newpage, struct page *page, bool sync)
> +	struct page *newpage, struct page *page, enum migrate_mode mode)
>  {
>  	if (PageDirty(page)) {
> -		if (!sync)
> +		/* Only writeback pages in full synchronous migration */
> +		if (mode != MIGRATE_SYNC)
>  			return -EBUSY;
>  		return writeout(mapping, page);
>  	}
> @@ -609,7 +613,7 @@ static int fallback_migrate_page(struct address_space *mapping,
>  	    !try_to_release_page(page, GFP_KERNEL))
>  		return -EAGAIN;
>  
> -	return migrate_page(mapping, newpage, page, sync);
> +	return migrate_page(mapping, newpage, page, mode);
>  }
>  
>  /*
> @@ -624,7 +628,7 @@ static int fallback_migrate_page(struct address_space *mapping,
>   *  == 0 - success
>   */
>  static int move_to_new_page(struct page *newpage, struct page *page,
> -					int remap_swapcache, bool sync)
> +				int remap_swapcache, enum migrate_mode mode)
>  {
>  	struct address_space *mapping;
>  	int rc;
> @@ -645,7 +649,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
>  
>  	mapping = page_mapping(page);
>  	if (!mapping)
> -		rc = migrate_page(mapping, newpage, page, sync);
> +		rc = migrate_page(mapping, newpage, page, mode);
>  	else if (mapping->a_ops->migratepage)
>  		/*
>  		 * Most pages have a mapping and most filesystems provide a
> @@ -654,9 +658,9 @@ static int move_to_new_page(struct page *newpage, struct page *page,
>  		 * is the most common path for page migration.
>  		 */
>  		rc = mapping->a_ops->migratepage(mapping,
> -						newpage, page, sync);
> +						newpage, page, mode);
>  	else
> -		rc = fallback_migrate_page(mapping, newpage, page, sync);
> +		rc = fallback_migrate_page(mapping, newpage, page, mode);
>  
>  	if (rc) {
>  		newpage->mapping = NULL;
> @@ -671,7 +675,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
>  }
>  
>  static int __unmap_and_move(struct page *page, struct page *newpage,
> -				int force, bool offlining, bool sync)
> +			int force, bool offlining, enum migrate_mode mode)
>  {
>  	int rc = -EAGAIN;
>  	int remap_swapcache = 1;
> @@ -680,7 +684,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>  	struct anon_vma *anon_vma = NULL;
>  
>  	if (!trylock_page(page)) {
> -		if (!force || !sync)
> +		if (!force || mode == MIGRATE_ASYNC)
>  			goto out;
>  
>  		/*
> @@ -726,10 +730,12 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>  
>  	if (PageWriteback(page)) {
>  		/*
> -		 * For !sync, there is no point retrying as the retry loop
> -		 * is expected to be too short for PageWriteback to be cleared
> +		 * Only in the case of a full syncronous migration is it
> +		 * necessary to wait for PageWriteback. In the async case,
> +		 * the retry loop is too short and in the sync-light case,
> +		 * the overhead of stalling is too much
>  		 */
> -		if (!sync) {
> +		if (mode != MIGRATE_SYNC) {
>  			rc = -EBUSY;
>  			goto uncharge;
>  		}
> @@ -800,7 +806,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>  
>  skip_unmap:
>  	if (!page_mapped(page))
> -		rc = move_to_new_page(newpage, page, remap_swapcache, sync);
> +		rc = move_to_new_page(newpage, page, remap_swapcache, mode);
>  
>  	if (rc && remap_swapcache)
>  		remove_migration_ptes(page, page);
> @@ -823,7 +829,8 @@ out:
>   * to the newly allocated page in newpage.
>   */
>  static int unmap_and_move(new_page_t get_new_page, unsigned long private,
> -			struct page *page, int force, bool offlining, bool sync)
> +			struct page *page, int force, bool offlining,
> +			enum migrate_mode mode)
>  {
>  	int rc = 0;
>  	int *result = NULL;
> @@ -843,7 +850,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
>  		if (unlikely(split_huge_page(page)))
>  			goto out;
>  
> -	rc = __unmap_and_move(page, newpage, force, offlining, sync);
> +	rc = __unmap_and_move(page, newpage, force, offlining, mode);
>  out:
>  	if (rc != -EAGAIN) {
>  		/*
> @@ -891,7 +898,8 @@ out:
>   */
>  static int unmap_and_move_huge_page(new_page_t get_new_page,
>  				unsigned long private, struct page *hpage,
> -				int force, bool offlining, bool sync)
> +				int force, bool offlining,
> +				enum migrate_mode mode)
>  {
>  	int rc = 0;
>  	int *result = NULL;
> @@ -904,7 +912,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  	rc = -EAGAIN;
>  
>  	if (!trylock_page(hpage)) {
> -		if (!force || !sync)
> +		if (!force || mode != MIGRATE_SYNC)
>  			goto out;
>  		lock_page(hpage);
>  	}
> @@ -915,7 +923,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  	try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
>  
>  	if (!page_mapped(hpage))
> -		rc = move_to_new_page(new_hpage, hpage, 1, sync);
> +		rc = move_to_new_page(new_hpage, hpage, 1, mode);
>  
>  	if (rc)
>  		remove_migration_ptes(hpage, hpage);
> @@ -958,7 +966,7 @@ out:
>   */
>  int migrate_pages(struct list_head *from,
>  		new_page_t get_new_page, unsigned long private, bool offlining,
> -		bool sync)
> +		enum migrate_mode mode)
>  {
>  	int retry = 1;
>  	int nr_failed = 0;
> @@ -979,7 +987,7 @@ int migrate_pages(struct list_head *from,
>  
>  			rc = unmap_and_move(get_new_page, private,
>  						page, pass > 2, offlining,
> -						sync);
> +						mode);
>  
>  			switch(rc) {
>  			case -ENOMEM:
> @@ -1009,7 +1017,7 @@ out:
>  
>  int migrate_huge_pages(struct list_head *from,
>  		new_page_t get_new_page, unsigned long private, bool offlining,
> -		bool sync)
> +		enum migrate_mode mode)
>  {
>  	int retry = 1;
>  	int nr_failed = 0;
> @@ -1026,7 +1034,7 @@ int migrate_huge_pages(struct list_head *from,
>  
>  			rc = unmap_and_move_huge_page(get_new_page,
>  					private, page, pass > 2, offlining,
> -					sync);
> +					mode);
>  
>  			switch(rc) {
>  			case -ENOMEM:
> @@ -1155,7 +1163,7 @@ set_status:
>  	err = 0;
>  	if (!list_empty(&pagelist)) {
>  		err = migrate_pages(&pagelist, new_page_node,
> -				(unsigned long)pm, 0, true);
> +				(unsigned long)pm, 0, MIGRATE_SYNC);
>  		if (err)
>  			putback_lru_pages(&pagelist);
>  	}
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

-- 
[]'s
Herton