Add following new vmstat events which will help in validating THP migration without split. Statistics reported through these new VM events will help in performance debugging.
1. THP_MIGRATION_SUCCESS 2. THP_MIGRATION_FAIL 3. THP_MIGRATION_SPLIT In addition, these new events also update normal page migration statistics appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAIL. While here, this updates current trace event 'mm_migrate_pages' to accommodate now available THP statistics. Cc: Jonathan Corbet <cor...@lwn.net> Cc: Steven Rostedt <rost...@goodmis.org> Cc: Ingo Molnar <mi...@redhat.com> Cc: Daniel Jordan <daniel.m.jor...@oracle.com> Cc: Hugh Dickins <hu...@google.com> Cc: Matthew Wilcox <wi...@infradead.org> Cc: Zi Yan <z...@nvidia.com> Cc: John Hubbard <jhubb...@nvidia.com> Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: linux-...@vger.kernel.org Cc: linux...@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Zi Yan <z...@nvidia.com> Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com> --- Applies on 5.8-rc4. Changes in V4: - Changed THP_MIGRATION_FAILURE as THP_MIGRATION_FAIL per John - Dropped all conditional 'if' blocks in migrate_pages() per Andrew and John - Updated migration events documentation per John - Updated thp_nr_pages variable as nr_subpages for an expected merge conflict - Moved all new THP vmstat events into CONFIG_MIGRATION - Updated Cc list with Documentation/ and tracing related addresses Changes in V3: (https://patchwork.kernel.org/patch/11647237/) - Formatted new events documentation with 'fmt' tool per Matthew - Made events universally available i.e dropped ARCH_ENABLE_THP_MIGRATION - Added THP_MIGRATION_SPLIT - Updated trace_mm_migrate_pages() with THP events - Made THP events update normal page migration events as well Changes in V2: (https://patchwork.kernel.org/patch/11586893/) - 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 | 27 +++++++++++++++ include/linux/vm_event_item.h | 3 ++ include/trace/events/migrate.h | 17 ++++++++-- mm/migrate.c | 52 ++++++++++++++++++++++++----- mm/vmstat.c | 3 ++ 5 files changed, 91 insertions(+), 11 deletions(-) diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst index 1d6cd7db4e43..68883ac485fa 100644 --- a/Documentation/vm/page_migration.rst +++ b/Documentation/vm/page_migration.rst @@ -253,5 +253,32 @@ 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. +Monitoring Migration +===================== + +The following events (counters) can be used to monitor page migration. + +1. PGMIGRATE_SUCCESS: Normal page migration success. Each count means that a + page was migrated. If the page was a non-THP page, then this counter is + increased by one. If the page was a THP, then this counter is increased by + the number of THP subpages. For example, migration of a single 2MB THP that + has 4KB-size base pages (subpages) will cause this counter to increase by + 512. + +2. PGMIGRATE_FAIL: Normal page migration failure. Same counting rules as for + _SUCCESS, above: this will be increased by the number of subpages, if it was + a THP. + +3. THP_MIGRATION_SUCCESS: A THP was migrated without being split. + +4. THP_MIGRATION_FAIL: A THP could not be migrated nor it could be split. + +5. THP_MIGRATION_SPLIT: A THP was migrated, but not as such: first, the THP had + to be split. After splitting, a migration retry was used for it's sub-pages. + +THP_MIGRATION_* events also update the appropriate PGMIGRATE_SUCCESS or +PGMIGRATE_FAIL events. For example, a THP migration failure will cause both +THP_MIGRATION_FAIL and PGMIGRATE_FAIL to increase. + 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 24fc7c3ae7d6..2e6ca53b9bbd 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -56,6 +56,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, #endif #ifdef CONFIG_MIGRATION PGMIGRATE_SUCCESS, PGMIGRATE_FAIL, + THP_MIGRATION_SUCCESS, + THP_MIGRATION_FAIL, + THP_MIGRATION_SPLIT, #endif #ifdef CONFIG_COMPACTION COMPACTMIGRATE_SCANNED, COMPACTFREE_SCANNED, diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h index 705b33d1e395..4d434398d64d 100644 --- a/include/trace/events/migrate.h +++ b/include/trace/events/migrate.h @@ -46,13 +46,18 @@ MIGRATE_REASON TRACE_EVENT(mm_migrate_pages, TP_PROTO(unsigned long succeeded, unsigned long failed, - enum migrate_mode mode, int reason), + unsigned long thp_succeeded, unsigned long thp_failed, + unsigned long thp_split, enum migrate_mode mode, int reason), - TP_ARGS(succeeded, failed, mode, reason), + TP_ARGS(succeeded, failed, thp_succeeded, thp_failed, + thp_split, mode, reason), TP_STRUCT__entry( __field( unsigned long, succeeded) __field( unsigned long, failed) + __field( unsigned long, thp_succeeded) + __field( unsigned long, thp_failed) + __field( unsigned long, thp_split) __field( enum migrate_mode, mode) __field( int, reason) ), @@ -60,13 +65,19 @@ TRACE_EVENT(mm_migrate_pages, TP_fast_assign( __entry->succeeded = succeeded; __entry->failed = failed; + __entry->thp_succeeded = thp_succeeded; + __entry->thp_failed = thp_failed; + __entry->thp_split = thp_split; __entry->mode = mode; __entry->reason = reason; ), - TP_printk("nr_succeeded=%lu nr_failed=%lu mode=%s reason=%s", + TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu mode=%s reason=%s", __entry->succeeded, __entry->failed, + __entry->thp_succeeded, + __entry->thp_failed, + __entry->thp_split, __print_symbolic(__entry->mode, MIGRATE_MODE), __print_symbolic(__entry->reason, MIGRATE_REASON)) ); diff --git a/mm/migrate.c b/mm/migrate.c index f37729673558..c706e3576cfc 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1429,22 +1429,35 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, enum migrate_mode mode, int reason) { int retry = 1; + int thp_retry = 1; int nr_failed = 0; int nr_succeeded = 0; + int nr_thp_succeeded = 0; + int nr_thp_failed = 0; + int nr_thp_split = 0; int pass = 0; + bool is_thp = false; struct page *page; struct page *page2; int swapwrite = current->flags & PF_SWAPWRITE; - int rc; + int rc, nr_subpages; if (!swapwrite) current->flags |= PF_SWAPWRITE; - for(pass = 0; pass < 10 && retry; pass++) { + for (pass = 0; pass < 10 && (retry || thp_retry); pass++) { retry = 0; + thp_retry = 0; list_for_each_entry_safe(page, page2, from, lru) { retry: + /* + * THP statistics is based on the source huge page. + * Capture required information that might get lost + * during migration. + */ + is_thp = PageTransHuge(page); + nr_subpages = hpage_nr_pages(page); cond_resched(); if (PageHuge(page)) @@ -1475,15 +1488,30 @@ 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); + nr_thp_split++; goto retry; } } + if (is_thp) { + nr_thp_failed++; + nr_failed += nr_subpages; + goto out; + } nr_failed++; goto out; case -EAGAIN: + if (is_thp) { + thp_retry++; + break; + } retry++; break; case MIGRATEPAGE_SUCCESS: + if (is_thp) { + nr_thp_succeeded++; + nr_succeeded += nr_subpages; + break; + } nr_succeeded++; break; default: @@ -1493,19 +1521,27 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, * removed from migration page list and not * retried in the next outer loop. */ + if (is_thp) { + nr_thp_failed++; + nr_failed += nr_subpages; + break; + } nr_failed++; break; } } } - nr_failed += retry; + nr_failed += retry + thp_retry; + nr_thp_failed += thp_retry; rc = nr_failed; out: - if (nr_succeeded) - count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); - if (nr_failed) - count_vm_events(PGMIGRATE_FAIL, nr_failed); - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason); + count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); + count_vm_events(PGMIGRATE_FAIL, nr_failed); + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); + count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); + trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded, + nr_thp_failed, nr_thp_split, mode, reason); if (!swapwrite) current->flags &= ~PF_SWAPWRITE; diff --git a/mm/vmstat.c b/mm/vmstat.c index 3fb23a21f6dd..09914a4bfee4 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1234,6 +1234,9 @@ const char * const vmstat_text[] = { #ifdef CONFIG_MIGRATION "pgmigrate_success", "pgmigrate_fail", + "thp_migration_success", + "thp_migration_fail", + "thp_migration_split", #endif #ifdef CONFIG_COMPACTION "compact_migrate_scanned", -- 2.20.1
