On Wed 12-12-12 16:43:35, Johannes Weiner wrote:
> In certain cases (kswapd reclaim, memcg target reclaim), a fixed
> minimum amount of pages is scanned from the LRU lists on each
> iteration, to make progress.
>
> Do not make this minimum bigger than the respective LRU list size,
> however, and save some busy work trying to isolate and reclaim pages
> that are not there.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Hmm, shrink_lruvec would do:
nr_to_scan = min_t(unsigned long,
nr[lru], SWAP_CLUSTER_MAX);
nr[lru] -= nr_to_scan;
and isolate_lru_pages does
for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++)
so it shouldn't matter and we shouldn't do any additional loops, right?
Anyway it would be beter if get_scan_count wouldn't ask for more than is
available.
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> include/linux/swap.h | 2 +-
> mm/vmscan.c | 10 ++++++----
> 2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 68df9c1..8c66486 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -156,7 +156,7 @@ enum {
> SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */
> };
>
> -#define SWAP_CLUSTER_MAX 32
> +#define SWAP_CLUSTER_MAX 32UL
> #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
>
> /*
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6e53446..1763e79 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1748,15 +1748,17 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> out:
> for_each_evictable_lru(lru) {
> int file = is_file_lru(lru);
> + unsigned long size;
> unsigned long scan;
>
> - scan = get_lru_size(lruvec, lru);
> + size = get_lru_size(lruvec, lru);
+ size = scan = get_lru_size(lruvec, lru);
> if (sc->priority || noswap) {
> - scan >>= sc->priority;
> + scan = size >> sc->priority;
> if (!scan && force_scan)
> - scan = SWAP_CLUSTER_MAX;
> + scan = min(size, SWAP_CLUSTER_MAX);
> scan = div64_u64(scan * fraction[file], denominator);
> - }
> + } else
> + scan = size;
And this is not necessary then but this is totally nit.
> nr[lru] = scan;
> }
> }
> --
> 1.7.11.7
>
--
Michal Hocko
SUSE Labs
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