On 9 Jul 2020, at 11:34, Randy Dunlap wrote:

Hi,

I have a few comments on this.

a. I reported it very early and should have been Cc-ed.

b. A patch that applies to mmotm or linux-next would have been better
than a full replacement patch.

c. I tried replacing what I believe is the correct/same patch file in mmotm
and still have build errors.

(more below)

On 7/9/20 2:39 AM, Anshuman Khandual wrote:

quoted

---
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(-)

quoted

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,

These 3 new symbols are still only present if CONFIG_MIGRATION=y, but the build errors
are using these symbols even when CONFIG_MIGRATION is not set.

quoted

 #endif
 #ifdef CONFIG_COMPACTION
 		COMPACTMIGRATE_SCANNED, COMPACTFREE_SCANNED,

quoted

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);

These references still cause build errors.

quoted

+	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",

Which arch are you building? I did not see any error
after applying this patch on mmotm (reverting the existing ones)
and compiling them on x86_64. I used make x86_64_defconfig and
unselected COMPACTION and MIGRATION.

mm/migrate.c and added vm events will not be used
if CONFIG_MIGRATION is unchecked. Why would they cause compilation errors?


—
Best Regards,
Yan Zi