On 06/20/2014 06:33 PM, Johannes Weiner wrote: > 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: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> (with a nitpick below) > --- > mm/vmscan.c | 67 ++++++++++++++++++++++++++++--------------------------------- > 1 file changed, 31 insertions(+), 36 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 19b5b8016209..ed1efb84c542 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -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. > + */ You moved this comment block left, yet you further shortened the individual lines, despite there is now more space to prolong them. > + 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(); > > @@ -2500,12 +2492,15 @@ 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; > > + if (sc->compaction_ready) > + goto out; > + > /* > * If we're getting trouble reclaiming, start doing > * writepage even in laptop mode. > @@ -2526,7 +2521,7 @@ 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(); > @@ -2535,7 +2530,7 @@ out: > 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 */ > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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