| Message ID | 20230206063313.635011-3-ying.huang@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | migrate_pages(): batch TLB flushing | expand |
在 2023/2/6 下午2:33, Huang Ying 写道: > This is a preparation patch to batch the folio unmapping and moving > for the non-hugetlb folios. Based on that we can batch the TLB > shootdown during the folio migration and make it possible to use some > hardware accelerator for the folio copying. > > In this patch the hugetlb folios and non-hugetlb folios migration is > separated in migrate_pages() to make it easy to change the non-hugetlb > folios migration implementation. > > Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > Cc: Zi Yan <ziy@nvidia.com> > Cc: Yang Shi <shy828301@gmail.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> > Cc: Minchan Kim <minchan@kernel.org> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> > --- > mm/migrate.c | 141 +++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 119 insertions(+), 22 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index ef388a9e4747..be7f37523463 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1396,6 +1396,8 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f > return rc; > } > > +#define NR_MAX_MIGRATE_PAGES_RETRY 10 > + > struct migrate_pages_stats { > int nr_succeeded; /* Normal and large folios migrated successfully, in > units of base pages */ > @@ -1406,6 +1408,95 @@ struct migrate_pages_stats { > int nr_thp_split; /* THP split before migrating */ > }; > > +/* > + * Returns the number of hugetlb folios that were not migrated, or an error code > + * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable > + * any more because the list has become empty or no retryable hugetlb folios > + * exist any more. It is caller's responsibility to call putback_movable_pages() > + * only if ret != 0. > + */ > +static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page, > + free_page_t put_new_page, unsigned long private, > + enum migrate_mode mode, int reason, > + struct migrate_pages_stats *stats, > + struct list_head *ret_folios) > +{ > + int retry = 1; > + int nr_failed = 0; > + int nr_retry_pages = 0; > + int pass = 0; > + struct folio *folio, *folio2; > + int rc, nr_pages; > + > + for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) { > + retry = 0; > + nr_retry_pages = 0; > + > + list_for_each_entry_safe(folio, folio2, from, lru) { > + if (!folio_test_hugetlb(folio)) > + continue; > + > + nr_pages = folio_nr_pages(folio); > + > + cond_resched(); Just curious, why put cond_resched() here, it makes "nr_pages = folio_nr_pages(folio)" looks Separately with below codes. > + > + rc = unmap_and_move_huge_page(get_new_page, > + put_new_page, private, > + &folio->page, pass > 2, mode, > + reason, ret_folios); > + /* > + * The rules are: > + * Success: hugetlb folio will be put back > + * -EAGAIN: stay on the from list > + * -ENOMEM: stay on the from list > + * -ENOSYS: stay on the from list > + * Other errno: put on ret_folios list > + */ > + switch(rc) { > + case -ENOSYS: > + /* Hugetlb migration is unsupported */ > + nr_failed++; > + stats->nr_failed_pages += nr_pages; > + list_move_tail(&folio->lru, ret_folios); > + break; > + case -ENOMEM: > + /* > + * When memory is low, don't bother to try to migrate > + * other folios, just exit. > + */ > + stats->nr_failed_pages += nr_pages + nr_retry_pages; > + return -ENOMEM; > + case -EAGAIN: > + retry++; > + nr_retry_pages += nr_pages; > + break; > + case MIGRATEPAGE_SUCCESS: > + stats->nr_succeeded += nr_pages; > + break; > + default: > + /* > + * Permanent failure (-EBUSY, etc.): > + * unlike -EAGAIN case, the failed folio is > + * removed from migration folio list and not > + * retried in the next outer loop. > + */ > + nr_failed++; > + stats->nr_failed_pages += nr_pages; > + break; > + } > + } > + } > + /* > + * nr_failed is number of hugetlb folios failed to be migrated. After > + * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb > + * folios as failed. > + */ > + nr_failed += retry; > + stats->nr_failed_pages += nr_retry_pages; > + > + return nr_failed; > +} > + > /* > * migrate_pages - migrate the folios specified in a list, to the free folios > * supplied as the target for the page migration > @@ -1422,10 +1513,10 @@ struct migrate_pages_stats { > * @ret_succeeded: Set to the number of folios migrated successfully if > * the caller passes a non-NULL pointer. > * > - * The function returns after 10 attempts or if no folios are movable any more > - * because the list has become empty or no retryable folios exist any more. > - * It is caller's responsibility to call putback_movable_pages() to return folios > - * to the LRU or free list only if ret != 0. > + * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios > + * are movable any more because the list has become empty or no retryable folios > + * exist any more. It is caller's responsibility to call putback_movable_pages() > + * only if ret != 0. > * > * Returns the number of {normal folio, large folio, hugetlb} that were not > * migrated, or an error code. The number of large folio splits will be > @@ -1439,7 +1530,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > int retry = 1; > int large_retry = 1; > int thp_retry = 1; > - int nr_failed = 0; > + int nr_failed; > int nr_retry_pages = 0; > int nr_large_failed = 0; > int pass = 0; > @@ -1456,38 +1547,45 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > trace_mm_migrate_pages_start(mode, reason); > > memset(&stats, 0, sizeof(stats)); > + rc = migrate_hugetlbs(from, get_new_page, put_new_page, private, mode, reason, > + &stats, &ret_folios); > + if (rc < 0) > + goto out; > + nr_failed = rc; > + > split_folio_migration: > - for (pass = 0; pass < 10 && (retry || large_retry); pass++) { > + for (pass = 0; > + pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry); > + pass++) { > retry = 0; > large_retry = 0; > thp_retry = 0; > nr_retry_pages = 0; > > list_for_each_entry_safe(folio, folio2, from, lru) { > + /* Retried hugetlb folios will be kept in list */ > + if (folio_test_hugetlb(folio)) { > + list_move_tail(&folio->lru, &ret_folios); > + continue; > + } > + > /* > * Large folio statistics is based on the source large > * folio. Capture required information that might get > * lost during migration. > */ > - is_large = folio_test_large(folio) && !folio_test_hugetlb(folio); > + is_large = folio_test_large(folio); > is_thp = is_large && folio_test_pmd_mappable(folio); > nr_pages = folio_nr_pages(folio); > + > cond_resched(); > > - if (folio_test_hugetlb(folio)) > - rc = unmap_and_move_huge_page(get_new_page, > - put_new_page, private, > - &folio->page, pass > 2, mode, > - reason, > - &ret_folios); > - else > - rc = unmap_and_move(get_new_page, put_new_page, > - private, folio, pass > 2, mode, > - reason, &ret_folios); > + rc = unmap_and_move(get_new_page, put_new_page, > + private, folio, pass > 2, mode, > + reason, &ret_folios); > /* > * The rules are: > - * Success: non hugetlb folio will be freed, hugetlb > - * folio will be put back > + * Success: folio will be freed > * -EAGAIN: stay on the from list > * -ENOMEM: stay on the from list > * -ENOSYS: stay on the from list > @@ -1514,7 +1612,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > stats.nr_thp_split += is_thp; > break; > } > - /* Hugetlb migration is unsupported */ > } else if (!no_split_folio_counting) { > nr_failed++; > } > @@ -1608,8 +1705,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > */ > if (!list_empty(&split_folios)) { > /* > - * Move non-migrated folios (after 10 retries) to ret_folios > - * to avoid migrating them again. > + * Move non-migrated folios (after NR_MAX_MIGRATE_PAGES_RETRY > + * retries) to ret_folios to avoid migrating them again. > */ > list_splice_init(from, &ret_folios); > list_splice_init(&split_folios, from); Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
haoxin <xhao@linux.alibaba.com> writes: > ( 2023/2/6 H2:33, Huang Ying S: >> This is a preparation patch to batch the folio unmapping and moving >> for the non-hugetlb folios. Based on that we can batch the TLB >> shootdown during the folio migration and make it possible to use some >> hardware accelerator for the folio copying. >> >> In this patch the hugetlb folios and non-hugetlb folios migration is >> separated in migrate_pages() to make it easy to change the non-hugetlb >> folios migration implementation. >> >> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> Cc: Zi Yan <ziy@nvidia.com> >> Cc: Yang Shi <shy828301@gmail.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> >> Cc: Minchan Kim <minchan@kernel.org> >> Cc: Mike Kravetz <mike.kravetz@oracle.com> >> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> >> --- >> mm/migrate.c | 141 +++++++++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 119 insertions(+), 22 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index ef388a9e4747..be7f37523463 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1396,6 +1396,8 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f >> return rc; >> } >> +#define NR_MAX_MIGRATE_PAGES_RETRY 10 >> + >> struct migrate_pages_stats { >> int nr_succeeded; /* Normal and large folios migrated successfully, in >> units of base pages */ >> @@ -1406,6 +1408,95 @@ struct migrate_pages_stats { >> int nr_thp_split; /* THP split before migrating */ >> }; >> +/* >> + * Returns the number of hugetlb folios that were not migrated, or an error code >> + * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable >> + * any more because the list has become empty or no retryable hugetlb folios >> + * exist any more. It is caller's responsibility to call putback_movable_pages() >> + * only if ret != 0. >> + */ >> +static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page, >> + free_page_t put_new_page, unsigned long private, >> + enum migrate_mode mode, int reason, >> + struct migrate_pages_stats *stats, >> + struct list_head *ret_folios) >> +{ >> + int retry = 1; >> + int nr_failed = 0; >> + int nr_retry_pages = 0; >> + int pass = 0; >> + struct folio *folio, *folio2; >> + int rc, nr_pages; >> + >> + for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) { >> + retry = 0; >> + nr_retry_pages = 0; >> + >> + list_for_each_entry_safe(folio, folio2, from, lru) { >> + if (!folio_test_hugetlb(folio)) >> + continue; >> + >> + nr_pages = folio_nr_pages(folio); >> + >> + cond_resched(); > Just curious, why put cond_resched() here, it makes > "nr_pages = folio_nr_pages(folio)" looks Separately with below > codes. This is the original behavior. Per my understanding, this can reduce the schedule latency of the page migration. >> + >> + rc = unmap_and_move_huge_page(get_new_page, >> + put_new_page, private, >> + &folio->page, pass > 2, mode, >> + reason, ret_folios); >> + /* >> + * The rules are: >> + * Success: hugetlb folio will be put back >> + * -EAGAIN: stay on the from list >> + * -ENOMEM: stay on the from list >> + * -ENOSYS: stay on the from list >> + * Other errno: put on ret_folios list >> + */ >> + switch(rc) { >> + case -ENOSYS: >> + /* Hugetlb migration is unsupported */ >> + nr_failed++; >> + stats->nr_failed_pages += nr_pages; >> + list_move_tail(&folio->lru, ret_folios); >> + break; >> + case -ENOMEM: >> + /* >> + * When memory is low, don't bother to try to migrate >> + * other folios, just exit. >> + */ >> + stats->nr_failed_pages += nr_pages + nr_retry_pages; >> + return -ENOMEM; >> + case -EAGAIN: >> + retry++; >> + nr_retry_pages += nr_pages; >> + break; >> + case MIGRATEPAGE_SUCCESS: >> + stats->nr_succeeded += nr_pages; >> + break; >> + default: >> + /* >> + * Permanent failure (-EBUSY, etc.): >> + * unlike -EAGAIN case, the failed folio is >> + * removed from migration folio list and not >> + * retried in the next outer loop. >> + */ >> + nr_failed++; >> + stats->nr_failed_pages += nr_pages; >> + break; >> + } >> + } >> + } >> + /* >> + * nr_failed is number of hugetlb folios failed to be migrated. After >> + * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb >> + * folios as failed. >> + */ >> + nr_failed += retry; >> + stats->nr_failed_pages += nr_retry_pages; >> + >> + return nr_failed; >> +} >> + >> /* >> * migrate_pages - migrate the folios specified in a list, to the free folios >> * supplied as the target for the page migration >> @@ -1422,10 +1513,10 @@ struct migrate_pages_stats { >> * @ret_succeeded: Set to the number of folios migrated successfully if >> * the caller passes a non-NULL pointer. >> * >> - * The function returns after 10 attempts or if no folios are movable any more >> - * because the list has become empty or no retryable folios exist any more. >> - * It is caller's responsibility to call putback_movable_pages() to return folios >> - * to the LRU or free list only if ret != 0. >> + * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios >> + * are movable any more because the list has become empty or no retryable folios >> + * exist any more. It is caller's responsibility to call putback_movable_pages() >> + * only if ret != 0. >> * >> * Returns the number of {normal folio, large folio, hugetlb} that were not >> * migrated, or an error code. The number of large folio splits will be >> @@ -1439,7 +1530,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> int retry = 1; >> int large_retry = 1; >> int thp_retry = 1; >> - int nr_failed = 0; >> + int nr_failed; >> int nr_retry_pages = 0; >> int nr_large_failed = 0; >> int pass = 0; >> @@ -1456,38 +1547,45 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> trace_mm_migrate_pages_start(mode, reason); >> memset(&stats, 0, sizeof(stats)); >> + rc = migrate_hugetlbs(from, get_new_page, put_new_page, private, mode, reason, >> + &stats, &ret_folios); >> + if (rc < 0) >> + goto out; >> + nr_failed = rc; >> + >> split_folio_migration: >> - for (pass = 0; pass < 10 && (retry || large_retry); pass++) { >> + for (pass = 0; >> + pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry); >> + pass++) { >> retry = 0; >> large_retry = 0; >> thp_retry = 0; >> nr_retry_pages = 0; >> list_for_each_entry_safe(folio, folio2, from, lru) { >> + /* Retried hugetlb folios will be kept in list */ >> + if (folio_test_hugetlb(folio)) { >> + list_move_tail(&folio->lru, &ret_folios); >> + continue; >> + } >> + >> /* >> * Large folio statistics is based on the source large >> * folio. Capture required information that might get >> * lost during migration. >> */ >> - is_large = folio_test_large(folio) && !folio_test_hugetlb(folio); >> + is_large = folio_test_large(folio); >> is_thp = is_large && folio_test_pmd_mappable(folio); >> nr_pages = folio_nr_pages(folio); >> + >> cond_resched(); >> - if (folio_test_hugetlb(folio)) >> - rc = unmap_and_move_huge_page(get_new_page, >> - put_new_page, private, >> - &folio->page, pass > 2, mode, >> - reason, >> - &ret_folios); >> - else >> - rc = unmap_and_move(get_new_page, put_new_page, >> - private, folio, pass > 2, mode, >> - reason, &ret_folios); >> + rc = unmap_and_move(get_new_page, put_new_page, >> + private, folio, pass > 2, mode, >> + reason, &ret_folios); >> /* >> * The rules are: >> - * Success: non hugetlb folio will be freed, hugetlb >> - * folio will be put back >> + * Success: folio will be freed >> * -EAGAIN: stay on the from list >> * -ENOMEM: stay on the from list >> * -ENOSYS: stay on the from list >> @@ -1514,7 +1612,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> stats.nr_thp_split += is_thp; >> break; >> } >> - /* Hugetlb migration is unsupported */ >> } else if (!no_split_folio_counting) { >> nr_failed++; >> } >> @@ -1608,8 +1705,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> */ >> if (!list_empty(&split_folios)) { >> /* >> - * Move non-migrated folios (after 10 retries) to ret_folios >> - * to avoid migrating them again. >> + * Move non-migrated folios (after NR_MAX_MIGRATE_PAGES_RETRY >> + * retries) to ret_folios to avoid migrating them again. >> */ >> list_splice_init(from, &ret_folios); >> list_splice_init(&split_folios, from); > Reviewed-by: Xin Hao <xhao@linux.alibaba.com> Thanks! Best Regards, Huang, Ying
diff --git a/mm/migrate.c b/mm/migrate.c index ef388a9e4747..be7f37523463 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1396,6 +1396,8 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f return rc; } +#define NR_MAX_MIGRATE_PAGES_RETRY 10 + struct migrate_pages_stats { int nr_succeeded; /* Normal and large folios migrated successfully, in units of base pages */ @@ -1406,6 +1408,95 @@ struct migrate_pages_stats { int nr_thp_split; /* THP split before migrating */ }; +/* + * Returns the number of hugetlb folios that were not migrated, or an error code + * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable + * any more because the list has become empty or no retryable hugetlb folios + * exist any more. It is caller's responsibility to call putback_movable_pages() + * only if ret != 0. + */ +static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page, + free_page_t put_new_page, unsigned long private, + enum migrate_mode mode, int reason, + struct migrate_pages_stats *stats, + struct list_head *ret_folios) +{ + int retry = 1; + int nr_failed = 0; + int nr_retry_pages = 0; + int pass = 0; + struct folio *folio, *folio2; + int rc, nr_pages; + + for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) { + retry = 0; + nr_retry_pages = 0; + + list_for_each_entry_safe(folio, folio2, from, lru) { + if (!folio_test_hugetlb(folio)) + continue; + + nr_pages = folio_nr_pages(folio); + + cond_resched(); + + rc = unmap_and_move_huge_page(get_new_page, + put_new_page, private, + &folio->page, pass > 2, mode, + reason, ret_folios); + /* + * The rules are: + * Success: hugetlb folio will be put back + * -EAGAIN: stay on the from list + * -ENOMEM: stay on the from list + * -ENOSYS: stay on the from list + * Other errno: put on ret_folios list + */ + switch(rc) { + case -ENOSYS: + /* Hugetlb migration is unsupported */ + nr_failed++; + stats->nr_failed_pages += nr_pages; + list_move_tail(&folio->lru, ret_folios); + break; + case -ENOMEM: + /* + * When memory is low, don't bother to try to migrate + * other folios, just exit. + */ + stats->nr_failed_pages += nr_pages + nr_retry_pages; + return -ENOMEM; + case -EAGAIN: + retry++; + nr_retry_pages += nr_pages; + break; + case MIGRATEPAGE_SUCCESS: + stats->nr_succeeded += nr_pages; + break; + default: + /* + * Permanent failure (-EBUSY, etc.): + * unlike -EAGAIN case, the failed folio is + * removed from migration folio list and not + * retried in the next outer loop. + */ + nr_failed++; + stats->nr_failed_pages += nr_pages; + break; + } + } + } + /* + * nr_failed is number of hugetlb folios failed to be migrated. After + * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb + * folios as failed. + */ + nr_failed += retry; + stats->nr_failed_pages += nr_retry_pages; + + return nr_failed; +} + /* * migrate_pages - migrate the folios specified in a list, to the free folios * supplied as the target for the page migration @@ -1422,10 +1513,10 @@ struct migrate_pages_stats { * @ret_succeeded: Set to the number of folios migrated successfully if * the caller passes a non-NULL pointer. * - * The function returns after 10 attempts or if no folios are movable any more - * because the list has become empty or no retryable folios exist any more. - * It is caller's responsibility to call putback_movable_pages() to return folios - * to the LRU or free list only if ret != 0. + * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios + * are movable any more because the list has become empty or no retryable folios + * exist any more. It is caller's responsibility to call putback_movable_pages() + * only if ret != 0. * * Returns the number of {normal folio, large folio, hugetlb} that were not * migrated, or an error code. The number of large folio splits will be @@ -1439,7 +1530,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, int retry = 1; int large_retry = 1; int thp_retry = 1; - int nr_failed = 0; + int nr_failed; int nr_retry_pages = 0; int nr_large_failed = 0; int pass = 0; @@ -1456,38 +1547,45 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, trace_mm_migrate_pages_start(mode, reason); memset(&stats, 0, sizeof(stats)); + rc = migrate_hugetlbs(from, get_new_page, put_new_page, private, mode, reason, + &stats, &ret_folios); + if (rc < 0) + goto out; + nr_failed = rc; + split_folio_migration: - for (pass = 0; pass < 10 && (retry || large_retry); pass++) { + for (pass = 0; + pass < NR_MAX_MIGRATE_PAGES_RETRY && (retry || large_retry); + pass++) { retry = 0; large_retry = 0; thp_retry = 0; nr_retry_pages = 0; list_for_each_entry_safe(folio, folio2, from, lru) { + /* Retried hugetlb folios will be kept in list */ + if (folio_test_hugetlb(folio)) { + list_move_tail(&folio->lru, &ret_folios); + continue; + } + /* * Large folio statistics is based on the source large * folio. Capture required information that might get * lost during migration. */ - is_large = folio_test_large(folio) && !folio_test_hugetlb(folio); + is_large = folio_test_large(folio); is_thp = is_large && folio_test_pmd_mappable(folio); nr_pages = folio_nr_pages(folio); + cond_resched(); - if (folio_test_hugetlb(folio)) - rc = unmap_and_move_huge_page(get_new_page, - put_new_page, private, - &folio->page, pass > 2, mode, - reason, - &ret_folios); - else - rc = unmap_and_move(get_new_page, put_new_page, - private, folio, pass > 2, mode, - reason, &ret_folios); + rc = unmap_and_move(get_new_page, put_new_page, + private, folio, pass > 2, mode, + reason, &ret_folios); /* * The rules are: - * Success: non hugetlb folio will be freed, hugetlb - * folio will be put back + * Success: folio will be freed * -EAGAIN: stay on the from list * -ENOMEM: stay on the from list * -ENOSYS: stay on the from list @@ -1514,7 +1612,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, stats.nr_thp_split += is_thp; break; } - /* Hugetlb migration is unsupported */ } else if (!no_split_folio_counting) { nr_failed++; } @@ -1608,8 +1705,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, */ if (!list_empty(&split_folios)) { /* - * Move non-migrated folios (after 10 retries) to ret_folios - * to avoid migrating them again. + * Move non-migrated folios (after NR_MAX_MIGRATE_PAGES_RETRY + * retries) to ret_folios to avoid migrating them again. */ list_splice_init(from, &ret_folios); list_splice_init(&split_folios, from);