On Wed, Dec 20, 2023 at 7:27 AM Dan Schatzberg <schatzberg.dan@xxxxxxxxx> wrote:
>
> We use the constants 0 and 200 in a few places in the mm code when
> referring to the min and max swappiness. This patch adds MIN_SWAPPINESS
> and MAX_SWAPPINESS #defines to improve clarity. There are no functional
> changes.
>
> Signed-off-by: Dan Schatzberg <schatzberg.dan@xxxxxxxxx>
> ---
> include/linux/swap.h | 2 ++
> mm/memcontrol.c | 2 +-
> mm/vmscan.c | 14 +++++++-------
> 3 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index f6dd6575b905..e2ab76c25b4a 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -407,6 +407,8 @@ extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>
> #define MEMCG_RECLAIM_MAY_SWAP (1 << 1)
> #define MEMCG_RECLAIM_PROACTIVE (1 << 2)
> +#define MIN_SWAPPINESS 0
> +#define MAX_SWAPPINESS 200
> extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
> unsigned long nr_pages,
> gfp_t gfp_mask,
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b226090fd906..fbe9f02dd206 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4337,7 +4337,7 @@ static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>
> - if (val > 200)
> + if (val > MAX_SWAPPINESS)
> return -EINVAL;
>
> if (!mem_cgroup_is_root(memcg))
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9dd8977de5a2..d91963e2d47f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -183,7 +183,7 @@ struct scan_control {
> #endif
>
> /*
> - * From 0 .. 200. Higher means more swappy.
> + * From 0 .. MAX_SWAPPINESS. Higher means more swappy.
> */
> int vm_swappiness = 60;
>
> @@ -2403,7 +2403,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> ap = swappiness * (total_cost + 1);
> ap /= anon_cost + 1;
>
> - fp = (200 - swappiness) * (total_cost + 1);
> + fp = (MAX_SWAPPINESS - swappiness) * (total_cost + 1);
> fp /= file_cost + 1;
>
> fraction[0] = ap;
> @@ -4400,7 +4400,7 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx
> {
> int type, tier;
> struct ctrl_pos sp, pv;
> - int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness };
> + int gain[ANON_AND_FILE] = { swappiness, MAX_SWAPPINESS - swappiness };
>
> /*
> * Compare the first tier of anon with that of file to determine which
> @@ -4436,7 +4436,7 @@ static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int sw
> /*
> * Try to make the obvious choice first. When anon and file are both
> * available from the same generation, interpret swappiness 1 as file
> - * first and 200 as anon first.
> + * first and MAX_SWAPPINESS as anon first.
> */
> if (!swappiness)
> type = LRU_GEN_FILE;
> @@ -4444,7 +4444,7 @@ static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int sw
> type = LRU_GEN_ANON;
> else if (swappiness == 1)
> type = LRU_GEN_FILE;
> - else if (swappiness == 200)
> + else if (swappiness == MAX_SWAPPINESS)
> type = LRU_GEN_ANON;
> else
> type = get_type_to_scan(lruvec, swappiness, &tier);
> @@ -5398,9 +5398,9 @@ static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
>
> lruvec = get_lruvec(memcg, nid);
>
> - if (swappiness < 0)
> + if (swappiness < MIN_SWAPPINESS)
> swappiness = get_swappiness(lruvec, sc);
> - else if (swappiness > 200)
> + else if (swappiness > MAX_SWAPPINESS)
> goto done;
>
> switch (cmd) {
> --
> 2.39.3
>
Sorry for being late to the party :) Was preoccupied with zswap convos.
Hmm these are all the occurrences of 0 and 200 (in the context of
swappiness) I can dig out. So, FWIW:
Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
