lkml.org 
[lkml]   [2020]   [May]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH 09/14] mm: deactivations shouldn't bias the LRU balance
    On Wed, May 20, 2020 at 07:25:20PM -0400, Johannes Weiner wrote:
    > Operations like MADV_FREE, FADV_DONTNEED etc. currently move any
    > affected active pages to the inactive list to accelerate their reclaim
    > (good) but also steer page reclaim toward that LRU type, or away from
    > the other (bad).
    >
    > The reason why this is undesirable is that such operations are not
    > part of the regular page aging cycle, and rather a fluke that doesn't
    > say much about the remaining pages on that list; they might all be in
    > heavy use, and once the chunk of easy victims has been purged, the VM
    > continues to apply elevated pressure on those remaining hot pages. The
    > other LRU, meanwhile, might have easily reclaimable pages, and there
    > was never a need to steer away from it in the first place.
    >
    > As the previous patch outlined, we should focus on recording actually
    > observed cost to steer the balance rather than speculating about the
    > potential value of one LRU list over the other. In that spirit, leave
    > explicitely deactivated pages to the LRU algorithm to pick up, and let
    > rotations decide which list is the easiest to reclaim.
    >
    > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
    > Acked-by: Minchan Kim <minchan@kernel.org>
    > Acked-by: Michal Hocko <mhocko@suse.com>
    > ---
    > mm/swap.c | 4 ----
    > 1 file changed, 4 deletions(-)
    >
    > diff --git a/mm/swap.c b/mm/swap.c
    > index 5d62c5a0c651..d7912bfb597f 100644
    > --- a/mm/swap.c
    > +++ b/mm/swap.c
    > @@ -515,14 +515,12 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
    >
    > if (active)
    > __count_vm_event(PGDEACTIVATE);
    > - lru_note_cost(lruvec, !file, hpage_nr_pages(page));
    > }
    >
    []

    mm/swap.c: In function 'lru_deactivate_file_fn':
    mm/swap.c:504:11: warning: variable 'file' set but not used
    [-Wunused-but-set-variable]
    int lru, file;
    ^~~~

    This?

    diff --git a/mm/swap.c b/mm/swap.c
    index fedf5847dfdb..9c38c1b545af 100644
    --- a/mm/swap.c
    +++ b/mm/swap.c
    @@ -501,7 +501,7 @@ void lru_cache_add_active_or_unevictable(struct page *page,
    static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
    void *arg)
    {
    - int lru, file;
    + int lru;
    bool active;

    if (!PageLRU(page))
    @@ -515,7 +515,6 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
    return;

    active = PageActive(page);
    - file = page_is_file_lru(page);
    lru = page_lru_base_type(page);

    del_page_from_lru_list(page, lruvec, lru + active);
    \
     
     \ /
      Last update: 2020-05-22 15:34    [W:3.258 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site