Re: [PATCH 1/8] migrate_pages: organize stats with struct migrate_pages_stats

Huang, Ying
2023-01-05T05:54:11Z

Alistair Popple <apopple@nvidia.com> writes:

> Huang Ying <ying.huang@intel.com> writes:
>
>> Define struct migrate_pages_stats to organize the various statistics
>> in migrate_pages(). This makes it easier to collect and consume the
>> statistics in multiple functions. This will be needed in the
>> following patches in the series.
>>
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> Cc: Zi Yan <ziy@nvidia.com>
>> Cc: Yang Shi <shy828301@gmail.com>
>> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Bharata B Rao <bharata@amd.com>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: haoxin <xhao@linux.alibaba.com>
>> ---
>> mm/migrate.c | 58 +++++++++++++++++++++++++++++-----------------------
>> 1 file changed, 32 insertions(+), 26 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index a4d3fc65085f..ec9263a33d38 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1396,6 +1396,14 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f
>> return rc;
>> }
>>
>> +struct migrate_pages_stats {
>> + int nr_succeeded;
>> + int nr_failed_pages;
>> + int nr_thp_succeeded;
>> + int nr_thp_failed;
>> + int nr_thp_split;
>
> I think some brief comments in the code for what each stat is tracking
> and their relationship to each other would be helpful (ie. does
> nr_succeeded include thp subpages, etc). Or at least a reference to
> where this is documented (ie. page_migration.rst) as I recall there has
> been some confusion in the past that has lead to bugs.

OK, will do that in the next version.

> Otherwise the patch looks good so:
>
> Reviewed-by: Alistair Popple <apopple@nvidia.com>

Thanks!

Best Regards,
Huang, Ying

>> +};
>> +
>> /*
>> * migrate_pages - migrate the folios specified in a list, to the free folios
>> * supplied as the target for the page migration
>> @@ -1430,13 +1438,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> int large_retry = 1;
>> int thp_retry = 1;
>> int nr_failed = 0;
>> - int nr_failed_pages = 0;
>> int nr_retry_pages = 0;
>> - int nr_succeeded = 0;
>> - int nr_thp_succeeded = 0;
>> int nr_large_failed = 0;
>> - int nr_thp_failed = 0;
>> - int nr_thp_split = 0;
>> int pass = 0;
>> bool is_large = false;
>> bool is_thp = false;
>> @@ -1446,9 +1449,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> LIST_HEAD(split_folios);
>> bool nosplit = (reason == MR_NUMA_MISPLACED);
>> bool no_split_folio_counting = false;
>> + struct migrate_pages_stats stats;
>>
>> trace_mm_migrate_pages_start(mode, reason);
>>
>> + memset(&stats, 0, sizeof(stats));
>> split_folio_migration:
>> for (pass = 0; pass < 10 && (retry || large_retry); pass++) {
>> retry = 0;
>> @@ -1502,9 +1507,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> /* Large folio migration is unsupported */
>> if (is_large) {
>> nr_large_failed++;
>> - nr_thp_failed += is_thp;
>> + stats.nr_thp_failed += is_thp;
>> if (!try_split_folio(folio, &split_folios)) {
>> - nr_thp_split += is_thp;
>> + stats.nr_thp_split += is_thp;
>> break;
>> }
>> /* Hugetlb migration is unsupported */
>> @@ -1512,7 +1517,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> nr_failed++;
>> }
>>
>> - nr_failed_pages += nr_pages;
>> + stats.nr_failed_pages += nr_pages;
>> list_move_tail(&folio->lru, &ret_folios);
>> break;
>> case -ENOMEM:
>> @@ -1522,13 +1527,13 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> */
>> if (is_large) {
>> nr_large_failed++;
>> - nr_thp_failed += is_thp;
>> + stats.nr_thp_failed += is_thp;
>> /* Large folio NUMA faulting doesn't split to retry. */
>> if (!nosplit) {
>> int ret = try_split_folio(folio, &split_folios);
>>
>> if (!ret) {
>> - nr_thp_split += is_thp;
>> + stats.nr_thp_split += is_thp;
>> break;
>> } else if (reason == MR_LONGTERM_PIN &&
>> ret == -EAGAIN) {
>> @@ -1546,7 +1551,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> nr_failed++;
>> }
>>
>> - nr_failed_pages += nr_pages + nr_retry_pages;
>> + stats.nr_failed_pages += nr_pages + nr_retry_pages;
>> /*
>> * There might be some split folios of fail-to-migrate large
>> * folios left in split_folios list. Move them back to migration
>> @@ -1556,7 +1561,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> list_splice_init(&split_folios, from);
>> /* nr_failed isn't updated for not used */
>> nr_large_failed += large_retry;
>> - nr_thp_failed += thp_retry;
>> + stats.nr_thp_failed += thp_retry;
>> goto out;
>> case -EAGAIN:
>> if (is_large) {
>> @@ -1568,8 +1573,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> nr_retry_pages += nr_pages;
>> break;
>> case MIGRATEPAGE_SUCCESS:
>> - nr_succeeded += nr_pages;
>> - nr_thp_succeeded += is_thp;
>> + stats.nr_succeeded += nr_pages;
>> + stats.nr_thp_succeeded += is_thp;
>> break;
>> default:
>> /*
>> @@ -1580,20 +1585,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> */
>> if (is_large) {
>> nr_large_failed++;
>> - nr_thp_failed += is_thp;
>> + stats.nr_thp_failed += is_thp;
>> } else if (!no_split_folio_counting) {
>> nr_failed++;
>> }
>>
>> - nr_failed_pages += nr_pages;
>> + stats.nr_failed_pages += nr_pages;
>> break;
>> }
>> }
>> }
>> nr_failed += retry;
>> nr_large_failed += large_retry;
>> - nr_thp_failed += thp_retry;
>> - nr_failed_pages += nr_retry_pages;
>> + stats.nr_thp_failed += thp_retry;
>> + stats.nr_failed_pages += nr_retry_pages;
>> /*
>> * Try to migrate split folios of fail-to-migrate large folios, no
>> * nr_failed counting in this round, since all split folios of a
>> @@ -1626,16 +1631,17 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>> if (list_empty(from))
>> rc = 0;
>>
>> - count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
>> - count_vm_events(PGMIGRATE_FAIL, nr_failed_pages);
>> - 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_pages, nr_thp_succeeded,
>> - nr_thp_failed, nr_thp_split, mode, reason);
>> + count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded);
>> + count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages);
>> + count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded);
>> + count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed);
>> + count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split);
>> + trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages,
>> + stats.nr_thp_succeeded, stats.nr_thp_failed,
>> + stats.nr_thp_split, mode, reason);
>>
>> if (ret_succeeded)
>> - *ret_succeeded = nr_succeeded;
>> + *ret_succeeded = stats.nr_succeeded;
>>
>> return rc;
>> }