Messages in this thread Patch in this message | | | From | "Huang, Ying" <> | Subject | [PATCH -V2] /proc/PID/smaps: Add PMD migration entry parsing | Date | Thu, 2 Apr 2020 10:00:31 +0800 |
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From: Huang Ying <ying.huang@intel.com>
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@intel.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> ---
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
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