diff --git a/mm/compaction.c b/mm/compaction.c index 7c675d6e9b333e85c4bcd8f34fec0ca3c1366223..83747368756d7ca0118e6312e575df926e968fba 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -285,13 +285,52 @@ void reset_isolation_suitable(pg_data_t *pgdat) } } +/* + * Sets the pageblock skip bit if it was clear. Note that this is a hint as + * locks are not required for read/writers. Returns true if it was already set. + */ +static bool test_and_set_skip(struct compact_control *cc, struct page *page, + unsigned long pfn) +{ + bool skip; + + /* Do no update if skip hint is being ignored */ + if (cc->ignore_skip_hint) + return false; + + if (!IS_ALIGNED(pfn, pageblock_nr_pages)) + return false; + + skip = get_pageblock_skip(page); + if (!skip && !cc->no_set_skip_hint) + set_pageblock_skip(page); + + return skip; +} + +static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) +{ + struct zone *zone = cc->zone; + + pfn = pageblock_end_pfn(pfn); + + /* Set for isolation rather than compaction */ + if (cc->no_set_skip_hint) + return; + + if (pfn > zone->compact_cached_migrate_pfn[0]) + zone->compact_cached_migrate_pfn[0] = pfn; + if (cc->mode != MIGRATE_ASYNC && + pfn > zone->compact_cached_migrate_pfn[1]) + zone->compact_cached_migrate_pfn[1] = pfn; +} + /* * If no pages were isolated then mark this pageblock to be skipped in the * future. The information is later cleared by __reset_isolation_suitable(). */ static void update_pageblock_skip(struct compact_control *cc, - struct page *page, unsigned long nr_isolated, - bool migrate_scanner) + struct page *page, unsigned long nr_isolated) { struct zone *zone = cc->zone; unsigned long pfn; @@ -310,16 +349,8 @@ static void update_pageblock_skip(struct compact_control *cc, pfn = page_to_pfn(page); /* Update where async and sync compaction should restart */ - if (migrate_scanner) { - if (pfn > zone->compact_cached_migrate_pfn[0]) - zone->compact_cached_migrate_pfn[0] = pfn; - if (cc->mode != MIGRATE_ASYNC && - pfn > zone->compact_cached_migrate_pfn[1]) - zone->compact_cached_migrate_pfn[1] = pfn; - } else { - if (pfn < zone->compact_cached_free_pfn) - zone->compact_cached_free_pfn = pfn; - } + if (pfn < zone->compact_cached_free_pfn) + zone->compact_cached_free_pfn = pfn; } #else static inline bool isolation_suitable(struct compact_control *cc, @@ -334,10 +365,19 @@ static inline bool pageblock_skip_persistent(struct page *page) } static inline void update_pageblock_skip(struct compact_control *cc, - struct page *page, unsigned long nr_isolated, - bool migrate_scanner) + struct page *page, unsigned long nr_isolated) { } + +static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) +{ +} + +static bool test_and_set_skip(struct compact_control *cc, struct page *page, + unsigned long pfn) +{ + return false; +} #endif /* CONFIG_COMPACTION */ /* @@ -567,7 +607,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, /* Update the pageblock-skip if the whole pageblock was scanned */ if (blockpfn == end_pfn) - update_pageblock_skip(cc, valid_page, total_isolated, false); + update_pageblock_skip(cc, valid_page, total_isolated); cc->total_free_scanned += nr_scanned; if (total_isolated) @@ -702,6 +742,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, unsigned long start_pfn = low_pfn; bool skip_on_failure = false; unsigned long next_skip_pfn = 0; + bool skip_updated = false; /* * Ensure that there are not too many pages isolated from the LRU @@ -768,8 +809,19 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, page = pfn_to_page(low_pfn); - if (!valid_page) + /* + * Check if the pageblock has already been marked skipped. + * Only the aligned PFN is checked as the caller isolates + * COMPACT_CLUSTER_MAX at a time so the second call must + * not falsely conclude that the block should be skipped. + */ + if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) { + if (!cc->ignore_skip_hint && get_pageblock_skip(page)) { + low_pfn = end_pfn; + goto isolate_abort; + } valid_page = page; + } /* * Skip if free. We read page order here without zone lock @@ -850,8 +902,19 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (!locked) { locked = compact_trylock_irqsave(zone_lru_lock(zone), &flags, cc); - if (!locked) + + /* Allow future scanning if the lock is contended */ + if (!locked) { + clear_pageblock_skip(page); break; + } + + /* Try get exclusive access under lock */ + if (!skip_updated) { + skip_updated = true; + if (test_and_set_skip(cc, page, low_pfn)) + goto isolate_abort; + } /* Recheck PageLRU and PageCompound under lock */ if (!PageLRU(page)) @@ -929,15 +992,20 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (unlikely(low_pfn > end_pfn)) low_pfn = end_pfn; +isolate_abort: if (locked) spin_unlock_irqrestore(zone_lru_lock(zone), flags); /* - * Update the pageblock-skip information and cached scanner pfn, - * if the whole pageblock was scanned without isolating any page. + * Updated the cached scanner pfn if the pageblock was scanned + * without isolating a page. The pageblock may not be marked + * skipped already if there were no LRU pages in the block. */ - if (low_pfn == end_pfn) - update_pageblock_skip(cc, valid_page, nr_isolated, true); + if (low_pfn == end_pfn && !nr_isolated) { + if (valid_page && !skip_updated) + set_pageblock_skip(valid_page); + update_cached_migrate(cc, low_pfn); + } trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, nr_scanned, nr_isolated); @@ -1323,8 +1391,6 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) nr_scanned++; free_pfn = page_to_pfn(freepage); if (free_pfn < high_pfn) { - update_fast_start_pfn(cc, free_pfn); - /* * Avoid if skipped recently. Ideally it would * move to the tail but even safe iteration of @@ -1341,6 +1407,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) /* Reorder to so a future search skips recent pages */ move_freelist_tail(freelist, freepage); + update_fast_start_pfn(cc, free_pfn); pfn = pageblock_start_pfn(free_pfn); cc->fast_search_fail = 0; set_pageblock_skip(freepage); @@ -1429,8 +1496,15 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, if (!page) continue; - /* If isolation recently failed, do not retry */ - if (!isolation_suitable(cc, page) && !fast_find_block) + /* + * If isolation recently failed, do not retry. Only check the + * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock + * to be visited multiple times. Assume skip was checked + * before making it "skip" so other compaction instances do + * not scan the same block. + */ + if (IS_ALIGNED(low_pfn, pageblock_nr_pages) && + !fast_find_block && !isolation_suitable(cc, page)) continue; /*