Add the following new VM events which will help in validating THP migration without split. Statistics reported through these new events will help in performance debugging.
1. THP_MIGRATION_SUCCESS 2. THP_MIGRATION_FAILURE THP_MIGRATION_FAILURE in particular represents an event when a THP could not be migrated as a single entity following an allocation failure and ended up getting split into constituent normal pages before being retried. This event, along with PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in quantifying and analyzing THP migration events including both success and failure cases. Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com> Cc: Zi Yan <z...@nvidia.com> Cc: John Hubbard <jhubb...@nvidia.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: linux...@kvack.org Cc: linux-kernel@vger.kernel.org [hughd: fixed oops on NULL newpage] Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com> --- Changes in V2: - Dropped PMD reference both from code and commit message per Matthew - Added documentation and updated the commit message per Daniel Changes in V1: (https://patchwork.kernel.org/patch/11564497/) - Changed function name as thp_pmd_migration_success() per John - Folded in a fix (https://patchwork.kernel.org/patch/11563009/) from Hugh Changes in RFC V2: (https://patchwork.kernel.org/patch/11554861/) - Decopupled and renamed VM events from their implementation per Zi and John - Added THP_PMD_MIGRATION_FAILURE VM event upon allocation failure and split Changes in RFC V1: (https://patchwork.kernel.org/patch/11542055/) Documentation/vm/page_migration.rst | 15 +++++++++++++++ include/linux/vm_event_item.h | 4 ++++ mm/migrate.c | 23 +++++++++++++++++++++++ mm/vmstat.c | 4 ++++ 4 files changed, 46 insertions(+) diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst index 1d6cd7db4e43..67e9b067fed7 100644 --- a/Documentation/vm/page_migration.rst +++ b/Documentation/vm/page_migration.rst @@ -253,5 +253,20 @@ which are function pointers of struct address_space_operations. PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag for own purpose. +Quantifying Migration +===================== +Following events can be used to quantify page migration. + +- PGMIGRATE_SUCCESS +- PGMIGRATE_FAIL +- THP_MIGRATION_SUCCESS +- THP_MIGRATION_FAILURE + +THP_MIGRATION_FAILURE in particular represents an event when a THP could not be +migrated as a single entity following an allocation failure and ended up getting +split into constituent normal pages before being retried. This event, along with +PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in quantifying and analyzing THP +migration events including both success and failure cases. + Christoph Lameter, May 8, 2006. Minchan Kim, Mar 28, 2016. diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index ffef0f279747..6459265461df 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -91,6 +91,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, THP_ZERO_PAGE_ALLOC_FAILED, THP_SWPOUT, THP_SWPOUT_FALLBACK, +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION + THP_MIGRATION_SUCCESS, + THP_MIGRATION_FAILURE, +#endif #endif #ifdef CONFIG_MEMORY_BALLOON BALLOON_INFLATE, diff --git a/mm/migrate.c b/mm/migrate.c index 7160c1556f79..0bb1dbb891bb 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1170,6 +1170,20 @@ static int __unmap_and_move(struct page *page, struct page *newpage, #define ICE_noinline #endif +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION +static inline void thp_migration_success(bool success) +{ + if (success) + count_vm_event(THP_MIGRATION_SUCCESS); + else + count_vm_event(THP_MIGRATION_FAILURE); +} +#else +static inline void thp_migration_success(bool success) +{ +} +#endif + /* * Obtain the lock on page, remove all ptes and migrate the page * to the newly allocated page in newpage. @@ -1232,6 +1246,14 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, * we want to retry. */ if (rc == MIGRATEPAGE_SUCCESS) { + /* + * When the page to be migrated has been freed from under + * us, that is considered a MIGRATEPAGE_SUCCESS, but no + * newpage has been allocated. It should not be counted + * as a successful THP migration. + */ + if (newpage && PageTransHuge(newpage)) + thp_migration_success(true); put_page(page); if (reason == MR_MEMORY_FAILURE) { /* @@ -1474,6 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, unlock_page(page); if (!rc) { list_safe_reset_next(page, page2, lru); + thp_migration_success(false); goto retry; } } diff --git a/mm/vmstat.c b/mm/vmstat.c index 96d21a792b57..4ce1ab2e9704 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1274,6 +1274,10 @@ const char * const vmstat_text[] = { "thp_zero_page_alloc_failed", "thp_swpout", "thp_swpout_fallback", +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION + "thp_migration_success", + "thp_migration_failure", +#endif #endif #ifdef CONFIG_MEMORY_BALLOON "balloon_inflate", -- 2.20.1
