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Message-ID: <20120731164203.GD3111@herton-Z68MA-D2H-B3>
Date: Tue, 31 Jul 2012 13:42:04 -0300
From: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To: Ben Hutchings <ben@...adent.org.uk>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
alan@...rguk.ukuu.org.uk, Mel Gorman <mgorman@...e.de>,
Rik van Riel <riel@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Minchan Kim <minchan.kim@...il.com>,
Dave Jones <davej@...hat.com>, Jan Kara <jack@...e.cz>,
Andy Isaacson <adi@...apodia.org>, Nai Xia <nai.xia@...il.com>,
Johannes Weiner <jweiner@...hat.com>
Subject: Re: [ 06/73] mm: compaction: introduce sync-light migration for use
by compaction
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@...e.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@...hat.com: This patch is heavily based on Andrea's work]
> [akpm@...ux-foundation.org: fix fs/nfs/write.c build]
> [akpm@...ux-foundation.org: fix fs/btrfs/disk-io.c build]
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> Reviewed-by: Rik van Riel <riel@...hat.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Minchan Kim <minchan.kim@...il.com>
> Cc: Dave Jones <davej@...hat.com>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Andy Isaacson <adi@...apodia.org>
> Cc: Nai Xia <nai.xia@...il.com>
> Cc: Johannes Weiner <jweiner@...hat.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Ben Hutchings <ben@...adent.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);
> }
>
>
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