On Tue, Feb 18, 2020 at 6:29 PM David Rientjes <rientjes@xxxxxxxxxx> wrote:
>
> The thp_fault_alloc and thp_fault_fallback vmstats are incremented when a
> hugepage is successfully or unsuccessfully allocated, respectively, during
> a page fault for anonymous memory.
>
> Extend this to shmem as well. Note that care is taken to increment
> thp_fault_alloc only when the fault succeeds; this is the same behavior as
> anonymous thp.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> mm/shmem.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> 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.
>
> spin_lock_irq(&info->lock);
> info->alloced += compound_nr(page);
>
