From: Huang Ying <ying.huang@xxxxxxxxx>
Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply
ignored. To improve the accuracy of /proc/PID/smaps, its parsing and processing
is added.
Before the patch, for a fully populated 400 MB anonymous VMA, sometimes some THP
pages under migration may be lost as follows.
7f3f6a7e5000-7f3f837e5000 rw-p 00000000 00:00 0
Size: 409600 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 407552 kB
Pss: 407552 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 407552 kB
Referenced: 301056 kB
Anonymous: 407552 kB
LazyFree: 0 kB
AnonHugePages: 405504 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 1
VmFlags: rd wr mr mw me ac
After the patch, it will be always,
7f3f6a7e5000-7f3f837e5000 rw-p 00000000 00:00 0
Size: 409600 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 409600 kB
Pss: 409600 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 409600 kB
Referenced: 294912 kB
Anonymous: 409600 kB
LazyFree: 0 kB
AnonHugePages: 407552 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 1
VmFlags: rd wr mr mw me ac
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
v2:
- Use thp_migration_supported() in condition to reduce code size if THP
migration isn't enabled.
- Replace VM_BUG_ON() with VM_WARN_ON_ONCE(), it's not necessary to nuking
kernel for this.
---
fs/proc/task_mmu.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8d382d4ec067..9c72f9ce2dd8 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -546,10 +546,19 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
struct mem_size_stats *mss = walk->private;
struct vm_area_struct *vma = walk->vma;
bool locked = !!(vma->vm_flags & VM_LOCKED);
- struct page *page;
+ struct page *page = NULL;
- /* FOLL_DUMP will return -EFAULT on huge zero page */
- page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+ if (pmd_present(*pmd)) {
+ /* FOLL_DUMP will return -EFAULT on huge zero page */
+ page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+ } else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) {
+ swp_entry_t entry = pmd_to_swp_entry(*pmd);
+
+ if (is_migration_entry(entry))
+ page = migration_entry_to_page(entry);
+ else
+ VM_WARN_ON_ONCE(1);
+ }
if (IS_ERR_OR_NULL(page))
return;
if (PageAnon(page))
@@ -578,8 +587,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
- if (pmd_present(*pmd))
- smaps_pmd_entry(pmd, addr, walk);
+ smaps_pmd_entry(pmd, addr, walk);
spin_unlock(ptl);
goto out;
}
--
2.25.0
