Add the following new trace events which will help in validating migration events involving PMD based THP pages.
1. THP_PMD_MIGRATION_ENTRY_SET 2. THP_PMD_MIGRATION_ENTRY_REMOVE There are no clear method to confirm whether a THP migration happened with out involving it's split. These trace events along with PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE will provide additional insights. After this change, A single 2M THP (2K base page) when migrated 1. Without split ................ pgmigrate_success 1 pgmigrate_fail 0 ................ thp_pmd_migration_entry_set 1 thp_pmd_migration_entry_remove 1 ................ 2. With split ................ pgmigrate_success 512 pgmigrate_fail 0 ................ thp_pmd_migration_entry_set 0 thp_pmd_migration_entry_remove 0 ................ pgmigrate_success as 1 instead of 512, provides a hint for possible THP migration event. But then it gets mixed with normal page migrations over time. These additional trace events provide required co-relation. Cc: Andrew Morton <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Cc: Zi Yan <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Anshuman Khandual <[email protected]> --- This is an indirect way for counting PMD migrations without split. Is there a better method possible ? Just request for comments at the moment. include/linux/vm_event_item.h | 4 ++++ mm/migrate.c | 1 + mm/rmap.c | 1 + mm/vmstat.c | 4 ++++ 4 files changed, 10 insertions(+) diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index ffef0f279747..4b25102cf3ad 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_PMD_MIGRATION_ENTRY_SET, + THP_PMD_MIGRATION_ENTRY_REMOVE, +#endif #endif #ifdef CONFIG_MEMORY_BALLOON BALLOON_INFLATE, diff --git a/mm/migrate.c b/mm/migrate.c index 7160c1556f79..8d50d55cbe97 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -228,6 +228,7 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, if (!pvmw.pte) { VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); remove_migration_pmd(&pvmw, new); + count_vm_event(THP_PMD_MIGRATION_ENTRY_REMOVE); continue; } #endif diff --git a/mm/rmap.c b/mm/rmap.c index f79a206b271a..3c1fe3f45cb5 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1418,6 +1418,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); set_pmd_migration_entry(&pvmw, page); + count_vm_event(THP_PMD_MIGRATION_ENTRY_SET); continue; } #endif diff --git a/mm/vmstat.c b/mm/vmstat.c index 96d21a792b57..a5254b7ee531 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_pmd_migration_entry_set", + "thp_pmd_migration_entry_remove", +#endif #endif #ifdef CONFIG_MEMORY_BALLOON "balloon_inflate", -- 2.20.1
