On 6/20/18 3:57 AM, Vlastimil Babka wrote:
On 06/19/2018 11:08 PM, Yang Shi wrote:Since commit eca56ff906bdd0239485e8b47154a6e73dd9a2f3 ("mm, shmem: add internal shmem resident memory accounting"), MM_SHMEMPAGES is added to separate the shmem accounting from regular files. So, all shmem pages should be accounted to MM_SHMEMPAGES instead of MM_FILEPAGES. And, normal 4K shmem pages have been accounted to MM_SHMEMPAGES, so shmem thp pages should be not treated differently. Accouting them to MM_SHMEMPAGES via mm_counter_file() since shmem pages are swap backed to keep consistent with normal 4K shmem pages. This will not change the rss counter of processes since shmem pages are still a part of it.<Andrew>So what are the user-visible effects of the patch then?</Andrew> Let's add this?: The /proc/pid/status and /proc/pid/statm counters will however be more accurate wrt shmem usage, as originally intended.
Thanks. Yes, other than this as commit eca56ff906bdd0239485e8b47154a6e73dd9a2f3 mentioned, oom also could report more accurate "shmem-rss"
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>Good catch, thanks. I guess the discrepancy happened due to the thp-tmpfs patchset existing externally for a long time and number of iterations, while commit eca56ff906bdd was merged, and nobody noticed that the thp case added more MM_FILEPAGES users. Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Thanks. Yang
--- mm/huge_memory.c | 4 ++-- mm/memory.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 1cd7c1a..2687f7c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1740,7 +1740,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, } else { if (arch_needs_pgtable_deposit()) zap_deposited_table(tlb->mm, pmd); - add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR); + add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); }spin_unlock(ptl);@@ -2088,7 +2088,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, SetPageReferenced(page); page_remove_rmap(page, true); put_page(page); - add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR); + add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); return; } else if (is_huge_zero_pmd(*pmd)) { /* diff --git a/mm/memory.c b/mm/memory.c index 7206a63..4a2f2a8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3372,7 +3372,7 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page) if (write) entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);- add_mm_counter(vma->vm_mm, MM_FILEPAGES, HPAGE_PMD_NR);+ add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR); page_add_file_rmap(page, true); /* * deposit and withdraw with pmd lock held
