The patch titled
Subject: mm: hugetlb: break COW earlier for resv owner
has been added to the -mm tree. Its filename is
mm-hugetlb-break-cow-earlier-for-resv-owner.patch
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From: Hillf Danton <dhillf@xxxxxxxxx>
Subject: mm: hugetlb: break COW earlier for resv owner
When a process owning a MAP_PRIVATE mapping fails to COW, due to
references held by a child and insufficient huge page pool, page is
unmapped from the child process to guarantee the original mappers
reliability, and the child may get SIGKILLed if it later faults.
With that guarantee, COW is broken earlier on behalf of owners, and they
will go less page faults.
Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff -puN mm/hugetlb.c~mm-hugetlb-break-cow-earlier-for-resv-owner mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-break-cow-earlier-for-resv-owner
+++ a/mm/hugetlb.c
@@ -2149,10 +2149,12 @@ int copy_hugetlb_page_range(struct mm_st
struct page *ptepage;
unsigned long addr;
int cow;
+ int owner;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+ owner = is_vma_resv_set(vma, HPAGE_RESV_OWNER);
for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
src_pte = huge_pte_offset(src, addr);
@@ -2168,10 +2170,19 @@ int copy_hugetlb_page_range(struct mm_st
spin_lock(&dst->page_table_lock);
spin_lock_nested(&src->page_table_lock, SINGLE_DEPTH_NESTING);
- if (!huge_pte_none(huge_ptep_get(src_pte))) {
+ entry = huge_ptep_get(src_pte);
+ if (!huge_pte_none(entry)) {
if (cow)
- huge_ptep_set_wrprotect(src, addr, src_pte);
- entry = huge_ptep_get(src_pte);
+ if (owner) {
+ /*
+ * Break COW for resv owner to go less
+ * page faults later
+ */
+ entry = huge_pte_wrprotect(entry);
+ } else {
+ huge_ptep_set_wrprotect(src, addr, src_pte);
+ entry = huge_ptep_get(src_pte);
+ }
ptepage = pte_page(entry);
get_page(ptepage);
page_dup_rmap(ptepage);
_
Subject: Subject: mm: hugetlb: break COW earlier for resv owner
Patches currently in -mm which might be from dhillf@xxxxxxxxx are
mm-vmscanc-cleanup-with-s-reclaim_mode-isolate_mode.patch
mm-vmscan-fix-misused-nr_reclaimed-in-shrink_mem_cgroup_zone.patch
vmscan-reclaim-at-order-0-when-compaction-is-enabled.patch
vmscan-kswapd-carefully-call-compaction.patch
vmscan-kswapd-carefully-call-compaction-fix.patch
vmscan-only-defer-compaction-for-failed-order-and-higher.patch
hugetlbfs-fix-hugetlb_get_unmapped_area.patch
hugetlb-drop-prev_vma-in-hugetlb_get_unmapped_area_topdown.patch
hugetlb-try-to-search-again-if-it-is-really-needed.patch
hugetlb-try-to-search-again-if-it-is-really-needed-fix.patch
mm-do-not-reset-cached_hole_size-when-vma-is-unmapped.patch
mm-search-from-free_area_cache-for-the-bigger-size.patch
mm-hugetlb-defer-freeing-pages-when-gathering-surplus-pages.patch
mm-vmscan-handle-isolated-pages-with-lru-lock-released.patch
mm-hugetlb-break-cow-earlier-for-resv-owner.patch
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