On Tue, 18 Feb 2020, Yang Shi wrote:
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -1502,9 +1502,8 @@ static struct page *shmem_alloc_page(gfp_t gfp,
> > return page;
> > }
> >
> > -static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
> > - struct inode *inode,
> > - pgoff_t index, bool huge)
> > +static struct page *shmem_alloc_and_acct_page(gfp_t gfp, struct inode *inode,
> > + pgoff_t index, bool fault, bool huge)
> > {
> > struct shmem_inode_info *info = SHMEM_I(inode);
> > struct page *page;
> > @@ -1518,9 +1517,11 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
> > if (!shmem_inode_acct_block(inode, nr))
> > goto failed;
> >
> > - if (huge)
> > + if (huge) {
> > page = shmem_alloc_hugepage(gfp, info, index);
> > - else
> > + if (!page && fault)
> > + count_vm_event(THP_FAULT_FALLBACK);
> > + } else
> > page = shmem_alloc_page(gfp, info, index);
> > if (page) {
> > __SetPageLocked(page);
> > @@ -1832,11 +1833,10 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> > }
> >
> > alloc_huge:
> > - page = shmem_alloc_and_acct_page(gfp, inode, index, true);
> > + page = shmem_alloc_and_acct_page(gfp, inode, index, vmf, true);
> > if (IS_ERR(page)) {
> > alloc_nohuge:
> > - page = shmem_alloc_and_acct_page(gfp, inode,
> > - index, false);
> > + page = shmem_alloc_and_acct_page(gfp, inode, index, vmf, false);
> > }
> > if (IS_ERR(page)) {
> > int retry = 5;
> > @@ -1871,8 +1871,11 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> >
> > error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
> > PageTransHuge(page));
> > - if (error)
> > + if (error) {
> > + if (vmf && PageTransHuge(page))
> > + count_vm_event(THP_FAULT_FALLBACK);
> > goto unacct;
> > + }
> > error = shmem_add_to_page_cache(page, mapping, hindex,
> > NULL, gfp & GFP_RECLAIM_MASK);
> > if (error) {
> > @@ -1883,6 +1886,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> > mem_cgroup_commit_charge(page, memcg, false,
> > PageTransHuge(page));
> > lru_cache_add_anon(page);
> > + if (vmf && PageTransHuge(page))
> > + count_vm_event(THP_FAULT_ALLOC);
>
> I think shmem THP alloc is accounted to THP_FILE_ALLOC. And it has
> been accounted by shmem_add_to_page_cache(). So, it sounds like a
> double count.
>
I think we can choose to either include file allocations into both
thp_fault_alloc and thp_fault_fallback or we can exclude them from both of
them. I don't think we can account for only one of them.
> >
> > spin_lock_irq(&info->lock);
> > info->alloced += compound_nr(page);
> >
>
