On Thu 19-10-17 20:26:57, Anshuman Khandual wrote:
> Its already assumed that the PageActive flag is clear on the input
> page, hence page_lru(page) will pick the base LRU for the page. In
> the same way page_lru(page) will pick active base LRU, once the
> flag PageActive is set on the page. This change of LRU list should
> happen implicitly through the page flags instead of being hard
> coded.
The patch description tells what but it doesn't explain _why_? Does the
resulting code is better, more optimized or is this a pure readability
thing?
All I can see is that page_lru is more complex and a large part of it
can be optimized away which has been done manually here. I suspect the
compiler can deduce the same thing.
> Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
> ---
> mm/swap.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/swap.c b/mm/swap.c
> index fcd82bc..494276b 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -275,12 +275,10 @@ static void __activate_page(struct page *page, struct
> lruvec *lruvec,
> {
> if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
> int file = page_is_file_cache(page);
> - int lru = page_lru_base_type(page);
>
> - del_page_from_lru_list(page, lruvec, lru);
> + del_page_from_lru_list(page, lruvec, page_lru(page));
> SetPageActive(page);
> - lru += LRU_ACTIVE;
> - add_page_to_lru_list(page, lruvec, lru);
> + add_page_to_lru_list(page, lruvec, page_lru(page));
> trace_mm_lru_activate(page);
>
> __count_vm_event(PGACTIVATE);
> --
> 1.8.5.2
--
Michal Hocko
SUSE Labs
