[Pmem] [PATCH 07/17] mm/vmscan: add helper for querying ability to age anonymous pages

From: Dave Hansen <dave.hansen(a)linux.intel.com> commit 2f368a9fb7f408ba7d4e6d588e1958fe8b780d08 upstream Anonymous pages are kept on their own LRU(s). These lists could theoretically always be scanned and maintained. But, without swap, there is currently nothing the kernel can *do* with the results of a scanned, sorted LRU for anonymous pages. A check for '!total_swap_pages' currently serves as a valid check as to whether anonymous LRUs should be maintained. However, another method will be added shortly: page demotion. Abstract out the 'total_swap_pages' checks into a helper, give it a logically significant name, and check for the possibility of page demotion. [dave.hansen(a)linux.intel.com: v11] Link: https://lkml.kernel.org/r/20210715055145.195411-7-ying.huang@intel.com Link: https://lkml.kernel.org/r/20210721063926.3024591-6-ying.huang@intel.com Link: https://lkml.kernel.org/r/20210715055145.195411-7-ying.huang@intel.com Signed-off-by: Dave Hansen <dave.hansen(a)linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang(a)intel.com> Reviewed-by: Yang Shi <shy828301(a)gmail.com> Reviewed-by: Greg Thelen <gthelen(a)google.com> Reviewed-by: Zi Yan <ziy(a)nvidia.com> Cc: Michal Hocko <mhocko(a)suse.com> Cc: Wei Xu <weixugc(a)google.com> Cc: Oscar Salvador <osalvador(a)suse.de> Cc: David Rientjes <rientjes(a)google.com> Cc: Dan Williams <dan.j.williams(a)intel.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Keith Busch <kbusch(a)kernel.org> Cc: Yang Shi <yang.shi(a)linux.alibaba.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org> Signed-off-by: Baolin Wang <baolin.wang(a)linux.alibaba.com> --- mm/vmscan.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 7dad7fb..682ede3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2489,6 +2489,21 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, } } +/* + * Anonymous LRU management is a waste if there is + * ultimately no way to reclaim the memory. + */ +static bool can_age_anon_pages(struct pglist_data *pgdat, + struct scan_control *sc) +{ + /* Aging the anon LRU is valuable if swap is present: */ + if (total_swap_pages > 0) + return true; + + /* Also valuable if anon pages can be demoted: */ + return can_demote(pgdat->node_id, sc); +} + static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) { unsigned long nr[NR_LRU_LISTS]; @@ -2598,7 +2613,8 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) * Even if we did not try to evict anon pages at all, we want to * rebalance the anon lru active/inactive ratio. */ - if (total_swap_pages && inactive_is_low(lruvec, LRU_INACTIVE_ANON)) + if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) && + inactive_is_low(lruvec, LRU_INACTIVE_ANON)) shrink_active_list(SWAP_CLUSTER_MAX, lruvec, sc, LRU_ACTIVE_ANON); } @@ -3469,7 +3485,7 @@ static void age_active_anon(struct pglist_data *pgdat, struct mem_cgroup *memcg; struct lruvec *lruvec; - if (!total_swap_pages) + if (!can_age_anon_pages(pgdat, sc)) return; lruvec = mem_cgroup_lruvec(NULL, pgdat); -- 1.8.3.1