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Date: Wed, 20 Aug 2014 20:48:18 -0300
From: Rafael Aquini <aquini@...hat.com>
To: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Sasha Levin <sasha.levin@...cle.com>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] mm/balloon_compaction: use common page ballooning
On Wed, Aug 20, 2014 at 07:05:04PM +0400, Konstantin Khlebnikov wrote:
> This patch replaces checking AS_BALLOON_MAP in page->mapping->flags
> with PageBalloon which is stored directly in the struct page.
>
> Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
> ---
> include/linux/balloon_compaction.h | 85 ++----------------------------------
> mm/Kconfig | 2 -
> mm/balloon_compaction.c | 7 +--
> mm/compaction.c | 9 ++--
> mm/migrate.c | 4 +-
> mm/vmscan.c | 2 -
> 6 files changed, 15 insertions(+), 94 deletions(-)
>
> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
> index 53d482e..f5fda8b 100644
> --- a/include/linux/balloon_compaction.h
> +++ b/include/linux/balloon_compaction.h
> @@ -108,77 +108,6 @@ static inline void balloon_mapping_free(struct address_space *balloon_mapping)
> }
>
> /*
> - * page_flags_cleared - helper to perform balloon @page ->flags tests.
> - *
> - * As balloon pages are obtained from buddy and we do not play with page->flags
> - * at driver level (exception made when we get the page lock for compaction),
> - * we can safely identify a ballooned page by checking if the
> - * PAGE_FLAGS_CHECK_AT_PREP page->flags are all cleared. This approach also
> - * helps us skip ballooned pages that are locked for compaction or release, thus
> - * mitigating their racy check at balloon_page_movable()
> - */
> -static inline bool page_flags_cleared(struct page *page)
> -{
> - return !(page->flags & PAGE_FLAGS_CHECK_AT_PREP);
> -}
> -
> -/*
> - * __is_movable_balloon_page - helper to perform @page mapping->flags tests
> - */
> -static inline bool __is_movable_balloon_page(struct page *page)
> -{
> - struct address_space *mapping = page->mapping;
> - return !PageAnon(page) && mapping_balloon(mapping);
> -}
> -
> -/*
> - * balloon_page_movable - test page->mapping->flags to identify balloon pages
> - * that can be moved by compaction/migration.
> - *
> - * This function is used at core compaction's page isolation scheme, therefore
> - * most pages exposed to it are not enlisted as balloon pages and so, to avoid
> - * undesired side effects like racing against __free_pages(), we cannot afford
> - * holding the page locked while testing page->mapping->flags here.
> - *
> - * As we might return false positives in the case of a balloon page being just
> - * released under us, the page->mapping->flags need to be re-tested later,
> - * under the proper page lock, at the functions that will be coping with the
> - * balloon page case.
> - */
> -static inline bool balloon_page_movable(struct page *page)
> -{
> - /*
> - * Before dereferencing and testing mapping->flags, let's make sure
> - * this is not a page that uses ->mapping in a different way
> - */
> - if (page_flags_cleared(page) && !page_mapped(page) &&
> - page_count(page) == 1)
> - return __is_movable_balloon_page(page);
> -
> - return false;
> -}
> -
> -/*
> - * isolated_balloon_page - identify an isolated balloon page on private
> - * compaction/migration page lists.
> - *
> - * After a compaction thread isolates a balloon page for migration, it raises
> - * the page refcount to prevent concurrent compaction threads from re-isolating
> - * the same page. For that reason putback_movable_pages(), or other routines
> - * that need to identify isolated balloon pages on private pagelists, cannot
> - * rely on balloon_page_movable() to accomplish the task.
> - */
> -static inline bool isolated_balloon_page(struct page *page)
> -{
> - /* Already isolated balloon pages, by default, have a raised refcount */
> - if (page_flags_cleared(page) && !page_mapped(page) &&
> - page_count(page) >= 2)
> - return __is_movable_balloon_page(page);
> -
> - return false;
> -}
> -
> -/*
> * balloon_page_insert - insert a page into the balloon's page list and make
> * the page->mapping assignment accordingly.
> * @page : page to be assigned as a 'balloon page'
> @@ -192,6 +121,7 @@ static inline void balloon_page_insert(struct page *page,
> struct address_space *mapping,
> struct list_head *head)
> {
> + __SetPageBalloon(page);
> page->mapping = mapping;
> list_add(&page->lru, head);
> }
> @@ -206,6 +136,7 @@ static inline void balloon_page_insert(struct page *page,
> */
> static inline void balloon_page_delete(struct page *page)
> {
> + __ClearPageBalloon(page);
> page->mapping = NULL;
> list_del(&page->lru);
> }
> @@ -250,24 +181,16 @@ static inline void balloon_page_insert(struct page *page,
> struct address_space *mapping,
> struct list_head *head)
> {
> + __SetPageBalloon(page);
> list_add(&page->lru, head);
> }
>
> static inline void balloon_page_delete(struct page *page)
> {
> + __ClearPageBalloon(page);
> list_del(&page->lru);
> }
>
> -static inline bool balloon_page_movable(struct page *page)
> -{
> - return false;
> -}
> -
> -static inline bool isolated_balloon_page(struct page *page)
> -{
> - return false;
> -}
> -
> static inline bool balloon_page_isolate(struct page *page)
> {
> return false;
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 72e0db0..e09cf0a 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -237,7 +237,7 @@ config MEMORY_BALLOON
> config BALLOON_COMPACTION
> bool "Allow for balloon memory compaction/migration"
> def_bool y
> - depends on COMPACTION && VIRTIO_BALLOON
> + depends on COMPACTION && MEMORY_BALLOON
> help
> Memory fragmentation introduced by ballooning might reduce
> significantly the number of 2MB contiguous memory blocks that can be
> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
> index 533c567..22c8e03 100644
> --- a/mm/balloon_compaction.c
> +++ b/mm/balloon_compaction.c
> @@ -253,8 +253,7 @@ bool balloon_page_isolate(struct page *page)
> * Prevent concurrent compaction threads from isolating
> * an already isolated balloon page by refcount check.
> */
> - if (__is_movable_balloon_page(page) &&
> - page_count(page) == 2) {
> + if (PageBalloon(page) && page_count(page) == 2) {
> __isolate_balloon_page(page);
> unlock_page(page);
> return true;
> @@ -275,7 +274,7 @@ void balloon_page_putback(struct page *page)
> */
> lock_page(page);
>
> - if (__is_movable_balloon_page(page)) {
> + if (PageBalloon(page)) {
> __putback_balloon_page(page);
> /* drop the extra ref count taken for page isolation */
> put_page(page);
> @@ -300,7 +299,7 @@ int balloon_page_migrate(struct page *newpage,
> */
> BUG_ON(!trylock_page(newpage));
>
> - if (WARN_ON(!__is_movable_balloon_page(page))) {
> + if (WARN_ON(!PageBalloon(page))) {
> dump_page(page, "not movable balloon page");
> unlock_page(newpage);
> return rc;
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 0653f5f..e9aeed2 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -596,11 +596,10 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
> * Skip any other type of page
> */
> if (!PageLRU(page)) {
> - if (unlikely(balloon_page_movable(page))) {
> - if (balloon_page_isolate(page)) {
> - /* Successfully isolated */
> - goto isolate_success;
> - }
> + if (unlikely(PageBalloon(page)) &&
> + balloon_page_isolate(page)) {
> + /* Successfully isolated */
> + goto isolate_success;
> }
> continue;
> }
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 161d044..c35e6f2 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -92,7 +92,7 @@ void putback_movable_pages(struct list_head *l)
> list_del(&page->lru);
> dec_zone_page_state(page, NR_ISOLATED_ANON +
> page_is_file_cache(page));
> - if (unlikely(isolated_balloon_page(page)))
> + if (unlikely(PageBalloon(page)))
> balloon_page_putback(page);
> else
> putback_lru_page(page);
> @@ -873,7 +873,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
> }
> }
>
> - if (unlikely(__is_movable_balloon_page(page))) {
> + if (unlikely(PageBalloon(page))) {
> /*
> * A ballooned page does not need any special attention from
> * physical to virtual reverse mapping procedures.
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2836b53..f90f93e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1160,7 +1160,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
>
> list_for_each_entry_safe(page, next, page_list, lru) {
> if (page_is_file_cache(page) && !PageDirty(page) &&
> - !isolated_balloon_page(page)) {
> + !PageBalloon(page)) {
> ClearPageActive(page);
> list_move(&page->lru, &clean_pages);
> }
>
Acked-by: Rafael Aquini <aquini@...hat.com>
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