Re: [ 28/41] mm: compaction: introduce sync-light migration for useby compaction
From: Herton Ronaldo Krzesinski
Date: Tue Jul 31 2012 - 12:43:37 EST
On Mon, Jul 30, 2012 at 10:31:27AM -0700, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> 3.0-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Mel Gorman <mgorman@xxxxxxx>
>
> 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@xxxxxxxxxx: This patch is heavily based on Andrea's work]
> [akpm@xxxxxxxxxxxxxxxxxxxx: fix fs/nfs/write.c build]
> [akpm@xxxxxxxxxxxxxxxxxxxx: fix fs/btrfs/disk-io.c build]
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
> Cc: Dave Jones <davej@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Andy Isaacson <adi@xxxxxxxxxxxxx>
> Cc: Nai Xia <nai.xia@xxxxxxxxx>
> Cc: Johannes Weiner <jweiner@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> ---
> 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(-)
>
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -801,7 +801,8 @@ static int btree_submit_bio_hook(struct
>
> #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,
> @@ -816,7 +817,7 @@ static int btree_migratepage(struct addr
> 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
>
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -569,7 +569,7 @@ static int hugetlbfs_set_page_dirty(stru
>
> static int hugetlbfs_migrate_page(struct address_space *mapping,
> struct page *newpage, struct page *page,
> - bool sync)
> + enum migrate_mode mode)
> {
> int rc;
>
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -315,7 +315,7 @@ void nfs_commit_release_pages(struct nfs
>
> #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
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1662,7 +1662,7 @@ 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
> @@ -1677,7 +1677,7 @@ int nfs_migrate_page(struct address_spac
>
> nfs_fscache_release_page(page, GFP_KERNEL);
>
> - return migrate_page(mapping, newpage, page, sync);
> + return migrate_page(mapping, newpage, page, mode);
> }
> #endif
>
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -523,6 +523,7 @@ enum positive_aop_returns {
> struct page;
> struct address_space;
> struct writeback_control;
> +enum migrate_mode;
>
> struct iov_iter {
> const struct iovec *iov;
> @@ -612,7 +613,7 @@ 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);
> @@ -2481,7 +2482,8 @@ extern int generic_check_addressable(uns
>
> #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
> --- 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_mappin
> 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; }
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -577,7 +577,7 @@ static int compact_zone(struct zone *zon
> 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;
>
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1464,7 +1464,7 @@ int soft_offline_page(struct page *page,
> 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",
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -747,7 +747,7 @@ do_migrate_range(unsigned long start_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);
> }
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -926,7 +926,7 @@ static int migrate_to_node(struct mm_str
>
> if (!list_empty(&pagelist)) {
> err = migrate_pages(&pagelist, new_node_page, dest,
> - false, true);
> + false, MIGRATE_SYNC);
> if (err)
> putback_lru_pages(&pagelist);
> }
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -222,12 +222,13 @@ 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);
> @@ -263,7 +264,7 @@ static bool buffer_migrate_lock_buffers(
> }
> #else
> static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
> - bool sync)
> + enum migrate_mode mode)
> {
> return true;
> }
> @@ -279,7 +280,7 @@ static inline bool buffer_migrate_lock_b
> */
> 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;
> @@ -315,7 +316,8 @@ static int migrate_page_move_mapping(str
> * 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;
> @@ -478,13 +480,14 @@ 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;
> @@ -501,17 +504,17 @@ 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;
> @@ -521,8 +524,8 @@ int buffer_migrate_page(struct address_s
> * 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));
> @@ -599,10 +602,11 @@ static int writeout(struct address_space
> * 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);
> }
> @@ -615,7 +619,7 @@ static int fallback_migrate_page(struct
> !try_to_release_page(page, GFP_KERNEL))
> return -EAGAIN;
>
> - return migrate_page(mapping, newpage, page, sync);
> + return migrate_page(mapping, newpage, page, mode);
> }
>
> /*
> @@ -630,7 +634,7 @@ static int fallback_migrate_page(struct
> * == 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;
> @@ -651,7 +655,7 @@ static int move_to_new_page(struct 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
> @@ -660,9 +664,9 @@ static int move_to_new_page(struct 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;
> @@ -677,7 +681,7 @@ static int move_to_new_page(struct 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;
> @@ -686,7 +690,7 @@ static int __unmap_and_move(struct page
> struct anon_vma *anon_vma = NULL;
>
> if (!trylock_page(page)) {
> - if (!force || !sync)
> + if (!force || mode == MIGRATE_ASYNC)
> goto out;
>
> /*
> @@ -732,10 +736,12 @@ static int __unmap_and_move(struct page
>
> 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;
> }
> @@ -806,7 +812,7 @@ static int __unmap_and_move(struct page
>
> 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);
> @@ -829,7 +835,8 @@ 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;
> @@ -847,7 +854,7 @@ static int unmap_and_move(new_page_t get
> 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) {
> /*
> @@ -895,7 +902,8 @@ 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;
> @@ -908,7 +916,7 @@ static int unmap_and_move_huge_page(new_
> rc = -EAGAIN;
>
> if (!trylock_page(hpage)) {
> - if (!force || !sync)
> + if (!force || mode != MIGRATE_SYNC)
> goto out;
> lock_page(hpage);
> }
> @@ -919,7 +927,7 @@ static int unmap_and_move_huge_page(new_
> 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);
> @@ -962,7 +970,7 @@ 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;
> @@ -983,7 +991,7 @@ 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:
> @@ -1013,7 +1021,7 @@ 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;
> @@ -1030,7 +1038,7 @@ int migrate_huge_pages(struct list_head
>
> rc = unmap_and_move_huge_page(get_new_page,
> private, page, pass > 2, offlining,
> - sync);
> + mode);
>
> switch(rc) {
> case -ENOMEM:
> @@ -1159,7 +1167,7 @@ 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);
> }
>
>
> --
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