diff options
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 9 | ||||
| -rw-r--r-- | include/trace/events/huge_memory.h | 1 | ||||
| -rw-r--r-- | mm/khugepaged.c | 69 |
3 files changed, 71 insertions, 8 deletions
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 8e3418ec4503..8ee78ec232eb 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -191,7 +191,14 @@ allocation failure to throttle the next allocation attempt:: /sys/kernel/mm/transparent_hugepage/khugepaged/alloc_sleep_millisecs -The khugepaged progress can be seen in the number of pages collapsed:: +The khugepaged progress can be seen in the number of pages collapsed (note +that this counter may not be an exact count of the number of pages +collapsed, since "collapsed" could mean multiple things: (1) A PTE mapping +being replaced by a PMD mapping, or (2) All 4K physical pages replaced by +one 2M hugepage. Each may happen independently, or together, depending on +the type of memory and the failures that occur. As such, this value should +be interpreted roughly as a sign of progress, and counters in /proc/vmstat +consulted for more accurate accounting):: /sys/kernel/mm/transparent_hugepage/khugepaged/pages_collapsed diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 55392bf30a03..fbbb25494d60 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -17,6 +17,7 @@ EM( SCAN_EXCEED_SHARED_PTE, "exceed_shared_pte") \ EM( SCAN_PTE_NON_PRESENT, "pte_non_present") \ EM( SCAN_PTE_UFFD_WP, "pte_uffd_wp") \ + EM( SCAN_PTE_MAPPED_HUGEPAGE, "pte_mapped_hugepage") \ EM( SCAN_PAGE_RO, "no_writable_page") \ EM( SCAN_LACK_REFERENCED_PAGE, "lack_referenced_page") \ EM( SCAN_PAGE_NULL, "page_null") \ diff --git a/mm/khugepaged.c b/mm/khugepaged.c index b3ebe90a66d9..b1e3f83c4eb2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -35,6 +35,7 @@ enum scan_result { SCAN_EXCEED_SHARED_PTE, SCAN_PTE_NON_PRESENT, SCAN_PTE_UFFD_WP, + SCAN_PTE_MAPPED_HUGEPAGE, SCAN_PAGE_RO, SCAN_LACK_REFERENCED_PAGE, SCAN_PAGE_NULL, @@ -1320,20 +1321,24 @@ static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot) * Notify khugepaged that given addr of the mm is pte-mapped THP. Then * khugepaged should try to collapse the page table. */ -static void khugepaged_add_pte_mapped_thp(struct mm_struct *mm, +static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) { struct khugepaged_mm_slot *mm_slot; struct mm_slot *slot; + bool ret = false; VM_BUG_ON(addr & ~HPAGE_PMD_MASK); spin_lock(&khugepaged_mm_lock); slot = mm_slot_lookup(mm_slots_hash, mm); mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); - if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) + if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) { mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; + ret = true; + } spin_unlock(&khugepaged_mm_lock); + return ret; } static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma, @@ -1370,9 +1375,16 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) pte_t *start_pte, *pte; pmd_t *pmd; spinlock_t *ptl; - int count = 0; + int count = 0, result = SCAN_FAIL; int i; + mmap_assert_write_locked(mm); + + /* Fast check before locking page if not PMD mapping PTE table */ + result = find_pmd_or_thp_or_none(mm, haddr, &pmd); + if (result != SCAN_SUCCEED) + return; + if (!vma || !vma->vm_file || !range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE)) return; @@ -1726,9 +1738,16 @@ static int collapse_file(struct mm_struct *mm, struct file *file, /* * If file was truncated then extended, or hole-punched, before * we locked the first page, then a THP might be there already. + * This will be discovered on the first iteration. */ if (PageTransCompound(page)) { - result = SCAN_PAGE_COMPOUND; + struct page *head = compound_head(page); + + result = compound_order(head) == HPAGE_PMD_ORDER && + head->index == start + /* Maybe PMD-mapped */ + ? SCAN_PTE_MAPPED_HUGEPAGE + : SCAN_PAGE_COMPOUND; goto out_unlock; } @@ -1962,11 +1981,23 @@ static int khugepaged_scan_file(struct mm_struct *mm, struct file *file, } /* - * XXX: khugepaged should compact smaller compound pages + * TODO: khugepaged should compact smaller compound pages * into a PMD sized page */ if (PageTransCompound(page)) { - result = SCAN_PAGE_COMPOUND; + struct page *head = compound_head(page); + + result = compound_order(head) == HPAGE_PMD_ORDER && + head->index == start + /* Maybe PMD-mapped */ + ? SCAN_PTE_MAPPED_HUGEPAGE + : SCAN_PAGE_COMPOUND; + /* + * For SCAN_PTE_MAPPED_HUGEPAGE, further processing + * by the caller won't touch the page cache, and so + * it's safe to skip LRU and refcount checks before + * returning. + */ break; } @@ -2026,6 +2057,12 @@ static int khugepaged_scan_file(struct mm_struct *mm, struct file *file, static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot) { } + +static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm, + unsigned long addr) +{ + return false; +} #endif static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, @@ -2118,8 +2155,26 @@ skip: &mmap_locked, cc); } - if (*result == SCAN_SUCCEED) + switch (*result) { + case SCAN_PTE_MAPPED_HUGEPAGE: { + pmd_t *pmd; + + *result = find_pmd_or_thp_or_none(mm, + khugepaged_scan.address, + &pmd); + if (*result != SCAN_SUCCEED) + break; + if (!khugepaged_add_pte_mapped_thp(mm, + khugepaged_scan.address)) + break; + } fallthrough; + case SCAN_SUCCEED: ++khugepaged_pages_collapsed; + break; + default: + break; + } + /* move to next address */ khugepaged_scan.address += HPAGE_PMD_SIZE; progress += HPAGE_PMD_NR; |