Messages in this thread | | | From | Dan Williams <> | Date | Thu, 26 Oct 2017 02:16:35 -0700 | Subject | Re: [PATCH v4] Add /proc/PID/smaps support for DAX |
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On Wed, Oct 25, 2017 at 10:13 PM, Fan Du <fan.du@intel.com> wrote: > > Memory behind device DAX is not attached into normal memory > management system, when user mmap /dev/dax, smaps part is > currently missing, so no idea for user to check how much > device DAX memory are actually used in practice. > > Whether vma is backed up by normal page,huge page, or both > at the same time, this makes no difference for device DAX > user so far. > > Using existing smaps structure is enough to do the job, so > this patch tries to use existing RSS/PSS stuff for statistics. > An example reading is like this: > ---------------------------------------------------- > 7f30fe200000-7f3102200000 rw-s 00000000 00:06 19567 /dev/dax12.0 > Size: 65536 kB > KernelPageSize: 4 kB > MMUPageSize: 4 kB > Rss: 65536 kB > Pss: 65536 kB > Shared_Clean: 0 kB > Shared_Dirty: 0 kB > Private_Clean: 0 kB > Private_Dirty: 65536 kB > Referenced: 65536 kB > Anonymous: 0 kB > LazyFree: 0 kB > AnonHugePages: 0 kB > ShmemPmdMapped: 0 kB > Shared_Hugetlb: 0 kB > Private_Hugetlb: 0 kB > Swap: 0 kB > SwapPss: 0 kB > Locked: 65536 kB > ProtectionKey: 0 > VmFlags: rd wr sh mr mw me ms mm hg > > Signed-off-by: Fan Du <fan.du@intel.com> > --- > v4: > * Merge device DAX readings into existing smap counters > for simplicity. > > v3: > * Elaborate more about the usage suggested by Michal Hocko > > v2: > * Using pte_devmap to check valid pfn page structure, > Pointed out by Dan. thx! > fs/proc/task_mmu.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 72 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 5589b4b..9b2d3e6 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -507,6 +507,55 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page, > } > } > > +/* page structure behind DAX mappings is NOT compound page > + * when it's a huge page mappings, so introduce new API to > + * account for both PMD and PUD mapping. > + */ > +static void smaps_account_dax_huge(struct mem_size_stats *mss, > + struct page *page, unsigned long size, bool young, bool dirty) > +{ > + int mapcount = page_mapcount(page); > + > + if (PageAnon(page)) { > + mss->anonymous += size; > + if (!PageSwapBacked(page) && !dirty && !PageDirty(page)) > + mss->lazyfree += size; > + } > + > + mss->resident += size; > + /* Accumulate the size in pages that have been accessed. */ > + if (young || page_is_young(page) || PageReferenced(page)) > + mss->referenced += size; > + > + /* > + * page_count(page) == 1 guarantees the page is mapped exactly once. > + * If any subpage of the compound page mapped with PTE it would elevate > + * page_count(). > + */ > + if (page_count(page) == 1) { > + if (dirty || PageDirty(page)) > + mss->private_dirty += size; > + else > + mss->private_clean += size; > + mss->pss += (u64)size << PSS_SHIFT; > + return; > + } > + > + if (mapcount >= 2) { > + if (dirty || PageDirty(page)) > + mss->shared_dirty += size; > + else > + mss->shared_clean += size; > + mss->pss += (size << PSS_SHIFT) / mapcount; > + } else { > + if (dirty || PageDirty(page)) > + mss->private_dirty += size; > + else > + mss->private_clean += size; > + mss->pss += size << PSS_SHIFT; > + } > +} > + > #ifdef CONFIG_SHMEM > static int smaps_pte_hole(unsigned long addr, unsigned long end, > struct mm_walk *walk) > @@ -528,7 +577,16 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, > struct page *page = NULL; > > if (pte_present(*pte)) { > - page = vm_normal_page(vma, addr, *pte); > + if (!vma_is_dax(vma)) > + page = vm_normal_page(vma, addr, *pte); > + else if (pte_devmap(*pte)) { > + struct dev_pagemap *pgmap; > + > + pgmap = get_dev_pagemap(pte_pfn(*pte), NULL);
Where do you do the put_dev_pagemap?
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