* Ingo Molnar <mingo@xxxxxxxxxx> wrote: > From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > > Add migrate_misplaced_page() which deals with migrating pages from > faults. > > This includes adding a new MIGRATE_FAULT migration mode to > deal with the extra page reference required due to having to look up > the page. [...] > --- a/include/linux/migrate_mode.h > +++ b/include/linux/migrate_mode.h > @@ -6,11 +6,14 @@ > * on most operations but not ->writepage as the potential stall time > * is too significant > * MIGRATE_SYNC will block when migrating pages > + * MIGRATE_FAULT called from the fault path to migrate-on-fault for mempolicy > + * this path has an extra reference count > */ Note, this is still the older, open-coded version. The newer replacement version created from Mel's patch which reuses migrate_pages() and is nicer on out-of-node-memory conditions and is cleaner all around can be found below. I tested it today and it appears to work fine. I noticed no performance improvement or performance drop from it - if it holds up in testing it will be part of the -v17 release of numa/core. Thanks, Ingo --------------------------> Subject: mm/migration: Introduce migrate_misplaced_page() From: Mel Gorman <mgorman@xxxxxxx> Date: Fri, 16 Nov 2012 11:22:23 +0000 Note: This was originally based on Peter's patch "mm/migrate: Introduce migrate_misplaced_page()" but borrows extremely heavily from Andrea's "autonuma: memory follows CPU algorithm and task/mm_autonuma stats collection". The end result is barely recognisable so signed-offs had to be dropped. If original authors are ok with it, I'll re-add the signed-off-bys. Add migrate_misplaced_page() which deals with migrating pages from faults. Based-on-work-by: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx> Based-on-work-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Based-on-work-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reviewed-by: Rik van Riel <riel@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Linux-MM <linux-mm@xxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Link: http://lkml.kernel.org/r/1353064973-26082-14-git-send-email-mgorman@xxxxxxx [ Adapted to the numa/core tree. ] Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- mm/memory.c | 13 ++----- mm/migrate.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 106 insertions(+), 10 deletions(-) Index: linux/mm/memory.c =================================================================== --- linux.orig/mm/memory.c +++ linux/mm/memory.c @@ -3494,28 +3494,25 @@ out_pte_upgrade_unlock: out_unlock: pte_unmap_unlock(ptep, ptl); -out: + if (page) { task_numa_fault(page_nid, last_cpu, 1); put_page(page); } - +out: return 0; migrate: pte_unmap_unlock(ptep, ptl); - if (!migrate_misplaced_page(page, node)) { - page_nid = node; + if (migrate_misplaced_page(page, node)) { goto out; } + page = NULL; ptep = pte_offset_map_lock(mm, pmd, address, &ptl); - if (!pte_same(*ptep, entry)) { - put_page(page); - page = NULL; + if (!pte_same(*ptep, entry)) goto out_unlock; - } goto out_pte_upgrade_unlock; } Index: linux/mm/migrate.c =================================================================== --- linux.orig/mm/migrate.c +++ linux/mm/migrate.c @@ -279,7 +279,7 @@ static int migrate_page_move_mapping(str struct page *newpage, struct page *page, struct buffer_head *head, enum migrate_mode mode) { - int expected_count; + int expected_count = 0; void **pslot; if (!mapping) { @@ -1403,4 +1403,103 @@ int migrate_vmas(struct mm_struct *mm, c } return err; } -#endif + +/* + * Returns true if this is a safe migration target node for misplaced NUMA + * pages. Currently it only checks the watermarks which crude + */ +static bool migrate_balanced_pgdat(struct pglist_data *pgdat, + int nr_migrate_pages) +{ + int z; + for (z = pgdat->nr_zones - 1; z >= 0; z--) { + struct zone *zone = pgdat->node_zones + z; + + if (!populated_zone(zone)) + continue; + + if (zone->all_unreclaimable) + continue; + + /* Avoid waking kswapd by allocating pages_to_migrate pages. */ + if (!zone_watermark_ok(zone, 0, + high_wmark_pages(zone) + + nr_migrate_pages, + 0, 0)) + continue; + return true; + } + return false; +} + +static struct page *alloc_misplaced_dst_page(struct page *page, + unsigned long data, + int **result) +{ + int nid = (int) data; + struct page *newpage; + + newpage = alloc_pages_exact_node(nid, + (GFP_HIGHUSER_MOVABLE | GFP_THISNODE | + __GFP_NOMEMALLOC | __GFP_NORETRY | + __GFP_NOWARN) & + ~GFP_IOFS, 0); + return newpage; +} + +/* + * Attempt to migrate a misplaced page to the specified destination + * node. Caller is expected to have an elevated reference count on + * the page that will be dropped by this function before returning. + */ +int migrate_misplaced_page(struct page *page, int node) +{ + int isolated = 0; + LIST_HEAD(migratepages); + + /* + * Don't migrate pages that are mapped in multiple processes. + * TODO: Handle false sharing detection instead of this hammer + */ + if (page_mapcount(page) != 1) + goto out; + + /* Avoid migrating to a node that is nearly full */ + if (migrate_balanced_pgdat(NODE_DATA(node), 1)) { + int page_lru; + + if (isolate_lru_page(page)) { + put_page(page); + goto out; + } + isolated = 1; + + /* + * Page is isolated which takes a reference count so now the + * callers reference can be safely dropped without the page + * disappearing underneath us during migration + */ + put_page(page); + + page_lru = page_is_file_cache(page); + inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru); + list_add(&page->lru, &migratepages); + } + + if (isolated) { + int nr_remaining; + + nr_remaining = migrate_pages(&migratepages, + alloc_misplaced_dst_page, + node, false, MIGRATE_ASYNC); + if (nr_remaining) { + putback_lru_pages(&migratepages); + isolated = 0; + } + } + BUG_ON(!list_empty(&migratepages)); +out: + return isolated; +} + +#endif /* CONFIG_NUMA */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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