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Message-ID: <20140623091220.GD9743@dhcp22.suse.cz>
Date: Mon, 23 Jun 2014 11:12:20 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 4/4] mm: vmscan: move swappiness out of scan_control
On Fri 20-06-14 12:33:50, Johannes Weiner wrote:
> Swappiness is determined for each scanned memcg individually in
> shrink_zone() and is not a parameter that applies throughout the
> reclaim scan. Move it out of struct scan_control to prevent
> accidental use of a stale value.
Yes, putting it into scan_control was a quick&dirty temporal
solution. I was thinking about something like lruvec_swappiness
(lruvec->mem_cgroup_per_zone->mem_cgroup) and stick it into
get_scan_count but what you have here is better because the swappiness
has memcg scope rather than lruvec.
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Acked-by: Michal Hocko <mhocko@...e.cz>
> ---
> mm/vmscan.c | 27 +++++++++++++--------------
> 1 file changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d0bc1a209746..757e2a8dbf58 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -89,9 +89,6 @@ struct scan_control {
> /* Scan (total_size >> priority) pages at once */
> int priority;
>
> - /* anon vs. file LRUs scanning "ratio" */
> - int swappiness;
> -
> /*
> * The memory cgroup that hit its limit and as a result is the
> * primary target of this reclaim invocation.
> @@ -1868,8 +1865,8 @@ enum scan_balance {
> * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
> * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
> */
> -static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> - unsigned long *nr)
> +static void get_scan_count(struct lruvec *lruvec, int swappiness,
> + struct scan_control *sc, unsigned long *nr)
> {
> struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
> u64 fraction[2];
> @@ -1912,7 +1909,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> * using the memory controller's swap limit feature would be
> * too expensive.
> */
> - if (!global_reclaim(sc) && !sc->swappiness) {
> + if (!global_reclaim(sc) && !swappiness) {
> scan_balance = SCAN_FILE;
> goto out;
> }
> @@ -1922,7 +1919,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> * system is close to OOM, scan both anon and file equally
> * (unless the swappiness setting disagrees with swapping).
> */
> - if (!sc->priority && sc->swappiness) {
> + if (!sc->priority && swappiness) {
> scan_balance = SCAN_EQUAL;
> goto out;
> }
> @@ -1965,7 +1962,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
> * With swappiness at 100, anonymous and file have the same priority.
> * This scanning priority is essentially the inverse of IO cost.
> */
> - anon_prio = sc->swappiness;
> + anon_prio = swappiness;
> file_prio = 200 - anon_prio;
>
> /*
> @@ -2055,7 +2052,8 @@ out:
> /*
> * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
> */
> -static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
> +static void shrink_lruvec(struct lruvec *lruvec, int swappiness,
> + struct scan_control *sc)
> {
> unsigned long nr[NR_LRU_LISTS];
> unsigned long targets[NR_LRU_LISTS];
> @@ -2066,7 +2064,7 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
> struct blk_plug plug;
> bool scan_adjusted;
>
> - get_scan_count(lruvec, sc, nr);
> + get_scan_count(lruvec, swappiness, sc, nr);
>
> /* Record the original scan target for proportional adjustments later */
> memcpy(targets, nr, sizeof(nr));
> @@ -2263,11 +2261,12 @@ static unsigned long shrink_zone(struct zone *zone, struct scan_control *sc)
> memcg = mem_cgroup_iter(root, NULL, &reclaim);
> do {
> struct lruvec *lruvec;
> + int swappiness;
>
> lruvec = mem_cgroup_zone_lruvec(zone, memcg);
> + swappiness = mem_cgroup_swappiness(memcg);
>
> - sc->swappiness = mem_cgroup_swappiness(memcg);
> - shrink_lruvec(lruvec, sc);
> + shrink_lruvec(lruvec, swappiness, sc);
>
> /*
> * Direct reclaim and kswapd have to scan all memory
> @@ -2714,10 +2713,10 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
> .may_swap = !noswap,
> .order = 0,
> .priority = 0,
> - .swappiness = mem_cgroup_swappiness(memcg),
> .target_mem_cgroup = memcg,
> };
> struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
> + int swappiness = mem_cgroup_swappiness(memcg);
>
> sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
> (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
> @@ -2733,7 +2732,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
> * will pick up pages from other mem cgroup's as well. We hack
> * the priority and make it zero.
> */
> - shrink_lruvec(lruvec, &sc);
> + shrink_lruvec(lruvec, swappiness, &sc);
>
> trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
>
> --
> 2.0.0
>
--
Michal Hocko
SUSE Labs
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