diff options
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 3 | ||||
| -rw-r--r-- | mm/khugepaged.c | 22 |
2 files changed, 17 insertions, 8 deletions
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index f82300b9193f..076443cc10a6 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -278,7 +278,8 @@ collapsed, resulting fewer pages being collapsed into THPs, and lower memory access performance. ``max_ptes_shared`` specifies how many pages can be shared across multiple -processes. Exceeding the number would block the collapse:: +processes. khugepaged might treat pages of THPs as shared if any page of +that THP is shared. Exceeding the number would block the collapse:: /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_shared diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 2f73d2aa9ae8..cf518fc44098 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -583,7 +583,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, folio = page_folio(page); VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); - if (page_mapcount(page) > 1) { + /* See hpage_collapse_scan_pmd(). */ + if (folio_likely_mapped_shared(folio)) { ++shared; if (cc->is_khugepaged && shared > khugepaged_max_ptes_shared) { @@ -1317,8 +1318,20 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, result = SCAN_PAGE_NULL; goto out_unmap; } + folio = page_folio(page); - if (page_mapcount(page) > 1) { + if (!folio_test_anon(folio)) { + result = SCAN_PAGE_ANON; + goto out_unmap; + } + + /* + * We treat a single page as shared if any part of the THP + * is shared. "False negatives" from + * folio_likely_mapped_shared() are not expected to matter + * much in practice. + */ + if (folio_likely_mapped_shared(folio)) { ++shared; if (cc->is_khugepaged && shared > khugepaged_max_ptes_shared) { @@ -1328,7 +1341,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, } } - folio = page_folio(page); /* * Record which node the original page is from and save this * information to cc->node_load[]. @@ -1349,10 +1361,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, result = SCAN_PAGE_LOCK; goto out_unmap; } - if (!folio_test_anon(folio)) { - result = SCAN_PAGE_ANON; - goto out_unmap; - } /* * Check if the page has any GUP (or other external) pins. |