On 11 Jun 16:47, Miaohe Lin wrote:
> nr_none is always 0 for non-shmem case because the page can be read from
> the backend store. So when nr_none ! = 0, it must be in is_shmem case.
> Also only adjust the nrpages and uncharge shmem when nr_none != 0 to save
> cpu cycles.
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/khugepaged.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 1b5dd3820eac..8e6fad7c7bd9 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1885,8 +1885,7 @@ static void collapse_file(struct mm_struct *mm,
>
> if (nr_none) {
> __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none);
> - if (is_shmem)
> - __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none);
> + __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none);
> }
Might be worth a small comment here - even though folks can see in above code
that this is only incremented in shmem path, might be nice to say why it's
always 0 for non-shmem (or conversely, why it's only possible to be non 0 on
shmem).
>
> /* Join all the small entries into a single multi-index entry */
> @@ -1950,10 +1949,10 @@ static void collapse_file(struct mm_struct *mm,
>
> /* Something went wrong: roll back page cache changes */
> xas_lock_irq(&xas);
> - mapping->nrpages -= nr_none;
> -
> - if (is_shmem)
> + if (nr_none) {
> + mapping->nrpages -= nr_none;
> shmem_uncharge(mapping->host, nr_none);
> + }
>
> xas_set(&xas, start);
> xas_for_each(&xas, page, end - 1) {
> --
> 2.23.0
>
>
Otherwise,
Reviewed-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
