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Subject[PATCH 24/31] mm, vmscan: Avoid passing in classzone_idx unnecessarily to compaction_ready
Date
The scan_control structure has enough information available for
compaction_ready() to make a decision. The classzone_idx manipulations in
shrink_zones() are no longer necessary as the highest populated zone is
no longer used to determine if shrink_slab should be called or not.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/vmscan.c | 28 ++++++++--------------------
1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6534fbe1b96f..c4094d7771a7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2521,7 +2521,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
* Returns true if compaction should go ahead for a high-order request, or
* the high-order allocation would succeed without compaction.
*/
-static inline bool compaction_ready(struct zone *zone, int order, int classzone_idx)
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
{
unsigned long watermark;
bool watermark_ok;
@@ -2532,21 +2532,21 @@ static inline bool compaction_ready(struct zone *zone, int order, int classzone_
* there is a buffer of free pages available to give compaction
* a reasonable chance of completing and allocating the page
*/
- watermark = high_wmark_pages(zone) + (2UL << order);
- watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, classzone_idx);
+ watermark = high_wmark_pages(zone) + (2UL << sc->order);
+ watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);

/*
* If compaction is deferred, reclaim up to a point where
* compaction will have a chance of success when re-enabled
*/
- if (compaction_deferred(zone, order))
+ if (compaction_deferred(zone, sc->order))
return watermark_ok;

/*
* If compaction is not ready to start and allocation is not likely
* to succeed without it, then keep reclaiming.
*/
- if (compaction_suitable(zone, order, 0, classzone_idx) == COMPACT_SKIPPED)
+ if (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx) == COMPACT_SKIPPED)
return false;

return watermark_ok;
@@ -2567,7 +2567,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
gfp_t orig_mask;
- enum zone_type classzone_idx;
pg_data_t *last_pgdat = NULL;

/*
@@ -2578,7 +2577,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
orig_mask = sc->gfp_mask;
if (buffer_heads_over_limit) {
sc->gfp_mask |= __GFP_HIGHMEM;
- sc->reclaim_idx = classzone_idx = gfp_zone(sc->gfp_mask);
+ sc->reclaim_idx = gfp_zone(sc->gfp_mask);
}

for_each_zone_zonelist_nodemask(zone, z, zonelist,
@@ -2587,17 +2586,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
continue;

/*
- * Note that reclaim_idx does not change as it is the highest
- * zone reclaimed from which for empty zones is a no-op but
- * classzone_idx is used by shrink_node to test if the slabs
- * should be shrunk on a given node.
- */
- classzone_idx = sc->reclaim_idx;
- while (!populated_zone(zone->zone_pgdat->node_zones +
- classzone_idx))
- classzone_idx--;
-
- /*
* Shrink each node in the zonelist once. If the zonelist is
* ordered by zone (not the default) then a node may be
* shrunk multiple times but in that case the user prefers
@@ -2631,8 +2619,8 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
*/
if (IS_ENABLED(CONFIG_COMPACTION) &&
sc->order > PAGE_ALLOC_COSTLY_ORDER &&
- zonelist_zone_idx(z) <= classzone_idx &&
- compaction_ready(zone, sc->order, classzone_idx)) {
+ zonelist_zone_idx(z) <= sc->reclaim_idx &&
+ compaction_ready(zone, sc)) {
sc->compaction_ready = true;
continue;
}
--
2.6.4
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