Commit 0b06496a authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

mm: vmscan: rework compaction-ready signaling in direct reclaim

Page reclaim for a higher-order page runs until compaction is ready,
then aborts and signals this situation through the return value of
shrink_zones().  This is an oddly specific signal to encode in the
return value of shrink_zones(), though, and can be quite confusing.

Introduce sc->compaction_ready and signal the compactability of the
zones out-of-band to free up the return value of shrink_zones() for
actual zone reclaimability.
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8d074293
......@@ -65,6 +65,9 @@ struct scan_control {
/* Number of pages freed so far during a call to shrink_zones() */
unsigned long nr_reclaimed;
/* One of the zones is ready for compaction */
int compaction_ready;
/* How many pages shrink_list() should reclaim */
unsigned long nr_to_reclaim;
......@@ -2292,15 +2295,11 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc)
}
/* Returns true if compaction should go ahead for a high-order request */
static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
static inline bool compaction_ready(struct zone *zone, int order)
{
unsigned long balance_gap, watermark;
bool watermark_ok;
/* Do not consider compaction for orders reclaim is meant to satisfy */
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
return false;
/*
* Compaction takes time to run and there are potentially other
* callers using the pages just freed. Continue reclaiming until
......@@ -2309,18 +2308,18 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
*/
balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);
watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
/*
* If compaction is deferred, reclaim up to a point where
* compaction will have a chance of success when re-enabled
*/
if (compaction_deferred(zone, sc->order))
if (compaction_deferred(zone, order))
return watermark_ok;
/* If compaction is not ready to start, keep reclaiming */
if (!compaction_suitable(zone, sc->order))
if (!compaction_suitable(zone, order))
return false;
return watermark_ok;
......@@ -2341,20 +2340,14 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
*
* If a zone is deemed to be full of pinned pages then just give it a light
* scan then give up on it.
*
* This function returns true if a zone is being reclaimed for a costly
* high-order allocation and compaction is ready to begin. This indicates to
* the caller that it should consider retrying the allocation instead of
* further reclaim.
*/
static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
{
struct zoneref *z;
struct zone *zone;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
unsigned long lru_pages = 0;
bool aborted_reclaim = false;
struct reclaim_state *reclaim_state = current->reclaim_state;
gfp_t orig_mask;
struct shrink_control shrink = {
......@@ -2391,22 +2384,24 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
if (sc->priority != DEF_PRIORITY &&
!zone_reclaimable(zone))
continue; /* Let kswapd poll it */
if (IS_ENABLED(CONFIG_COMPACTION)) {
/*
* If we already have plenty of memory free for
* compaction in this zone, don't free any more.
* Even though compaction is invoked for any
* non-zero order, only frequent costly order
* reclamation is disruptive enough to become a
* noticeable problem, like transparent huge
* page allocations.
*/
if ((zonelist_zone_idx(z) <= requested_highidx)
&& compaction_ready(zone, sc)) {
aborted_reclaim = true;
continue;
}
/*
* If we already have plenty of memory free for
* compaction in this zone, don't free any more.
* Even though compaction is invoked for any
* non-zero order, only frequent costly order
* reclamation is disruptive enough to become a
* noticeable problem, like transparent huge
* page allocations.
*/
if (IS_ENABLED(CONFIG_COMPACTION) &&
sc->order > PAGE_ALLOC_COSTLY_ORDER &&
zonelist_zone_idx(z) <= requested_highidx &&
compaction_ready(zone, sc->order)) {
sc->compaction_ready = true;
continue;
}
/*
* This steals pages from memory cgroups over softlimit
* and returns the number of reclaimed pages and
......@@ -2444,8 +2439,6 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
* promoted it to __GFP_HIGHMEM.
*/
sc->gfp_mask = orig_mask;
return aborted_reclaim;
}
/* All zones in zonelist are unreclaimable? */
......@@ -2489,7 +2482,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
{
unsigned long total_scanned = 0;
unsigned long writeback_threshold;
bool aborted_reclaim;
delayacct_freepages_start();
......@@ -2500,11 +2492,14 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
sc->priority);
sc->nr_scanned = 0;
aborted_reclaim = shrink_zones(zonelist, sc);
shrink_zones(zonelist, sc);
total_scanned += sc->nr_scanned;
if (sc->nr_reclaimed >= sc->nr_to_reclaim)
goto out;
break;
if (sc->compaction_ready)
break;
/*
* If we're getting trouble reclaiming, start doing
......@@ -2526,16 +2521,15 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
WB_REASON_TRY_TO_FREE_PAGES);
sc->may_writepage = 1;
}
} while (--sc->priority >= 0 && !aborted_reclaim);
} while (--sc->priority >= 0);
out:
delayacct_freepages_end();
if (sc->nr_reclaimed)
return sc->nr_reclaimed;
/* Aborted reclaim to try compaction? don't OOM, then */
if (aborted_reclaim)
if (sc->compaction_ready)
return 1;
/* top priority shrink_zones still had more to do? don't OOM, then */
......
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