diff options
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 6 | ||||
| -rw-r--r-- | include/linux/khugepaged.h | 1 | ||||
| -rw-r--r-- | include/linux/vm_event_item.h | 1 | ||||
| -rw-r--r-- | mm/huge_memory.c | 60 | ||||
| -rw-r--r-- | mm/khugepaged.c | 3 | ||||
| -rw-r--r-- | mm/vmstat.c | 1 |
6 files changed, 69 insertions, 3 deletions
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 56a086900651..aca0cff852b8 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -471,6 +471,12 @@ thp_deferred_split_page splitting it would free up some memory. Pages on split queue are going to be split under memory pressure. +thp_underused_split_page + is incremented when a huge page on the split queue was split + because it was underused. A THP is underused if the number of + zero pages in the THP is above a certain threshold + (/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none). + thp_split_pmd is incremented every time a PMD split into table of PTEs. This can happen, for instance, when application calls mprotect() or diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h index f68865e19b0b..30baae91b225 100644 --- a/include/linux/khugepaged.h +++ b/include/linux/khugepaged.h @@ -4,6 +4,7 @@ #include <linux/sched/coredump.h> /* MMF_VM_HUGEPAGE */ +extern unsigned int khugepaged_max_ptes_none __read_mostly; #ifdef CONFIG_TRANSPARENT_HUGEPAGE extern struct attribute_group khugepaged_attr_group; diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index aae5c7c5cfb4..aed952d04132 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -105,6 +105,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, THP_SPLIT_PAGE, THP_SPLIT_PAGE_FAILED, THP_DEFERRED_SPLIT_PAGE, + THP_UNDERUSED_SPLIT_PAGE, THP_SPLIT_PMD, THP_SCAN_EXCEED_NONE_PTE, THP_SCAN_EXCEED_SWAP_PTE, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9bc435bef2e6..cec5bce046a0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1187,6 +1187,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); mm_inc_nr_ptes(vma->vm_mm); + deferred_split_folio(folio, false); spin_unlock(vmf->ptl); count_vm_event(THP_FAULT_ALLOC); count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC); @@ -3608,6 +3609,39 @@ static unsigned long deferred_split_count(struct shrinker *shrink, return READ_ONCE(ds_queue->split_queue_len); } +static bool thp_underused(struct folio *folio) +{ + int num_zero_pages = 0, num_filled_pages = 0; + void *kaddr; + int i; + + if (khugepaged_max_ptes_none == HPAGE_PMD_NR - 1) + return false; + + for (i = 0; i < folio_nr_pages(folio); i++) { + kaddr = kmap_local_folio(folio, i * PAGE_SIZE); + if (!memchr_inv(kaddr, 0, PAGE_SIZE)) { + num_zero_pages++; + if (num_zero_pages > khugepaged_max_ptes_none) { + kunmap_local(kaddr); + return true; + } + } else { + /* + * Another path for early exit once the number + * of non-zero filled pages exceeds threshold. + */ + num_filled_pages++; + if (num_filled_pages >= HPAGE_PMD_NR - khugepaged_max_ptes_none) { + kunmap_local(kaddr); + return false; + } + } + kunmap_local(kaddr); + } + return false; +} + static unsigned long deferred_split_scan(struct shrinker *shrink, struct shrink_control *sc) { @@ -3645,13 +3679,35 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); list_for_each_entry_safe(folio, next, &list, _deferred_list) { + bool did_split = false; + bool underused = false; + + if (!folio_test_partially_mapped(folio)) { + underused = thp_underused(folio); + if (!underused) + goto next; + } if (!folio_trylock(folio)) goto next; - /* split_huge_page() removes page from list on success */ - if (!split_folio(folio)) + if (!split_folio(folio)) { + did_split = true; + if (underused) + count_vm_event(THP_UNDERUSED_SPLIT_PAGE); split++; + } folio_unlock(folio); next: + /* + * split_folio() removes folio from list on success. + * Only add back to the queue if folio is partially mapped. + * If thp_underused returns false, or if split_folio fails + * in the case it was underused, then consider it used and + * don't add it back to split_queue. + */ + if (!did_split && !folio_test_partially_mapped(folio)) { + list_del_init(&folio->_deferred_list); + ds_queue->split_queue_len--; + } folio_put(folio); } diff --git a/mm/khugepaged.c b/mm/khugepaged.c index ab646018ce25..32100041aef3 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -85,7 +85,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); * * Note that these are only respected if collapse was initiated by khugepaged. */ -static unsigned int khugepaged_max_ptes_none __read_mostly; +unsigned int khugepaged_max_ptes_none __read_mostly; static unsigned int khugepaged_max_ptes_swap __read_mostly; static unsigned int khugepaged_max_ptes_shared __read_mostly; @@ -1237,6 +1237,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, pgtable_trans_huge_deposit(mm, pmd, pgtable); set_pmd_at(mm, address, pmd, _pmd); update_mmu_cache_pmd(vma, address, pmd); + deferred_split_folio(folio, false); spin_unlock(pmd_ptl); folio = NULL; diff --git a/mm/vmstat.c b/mm/vmstat.c index aea58e9fce60..b5a4cea423e1 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1385,6 +1385,7 @@ const char * const vmstat_text[] = { "thp_split_page", "thp_split_page_failed", "thp_deferred_split_page", + "thp_underused_split_page", "thp_split_pmd", "thp_scan_exceed_none_pte", "thp_scan_exceed_swap_pte", |