During global reclaim, the nr_reclaimed passed to vmpressure includes the pages reclaimed from slab. But the corresponding scanned slab pages is not passed. This can cause total reclaimed pages to be greater than scanned, causing an unsigned underflow in vmpressure resulting in a critical event being sent to root cgroup. So do not consider reclaimed slab pages for vmpressure calculation. The reclaimed pages from slab can be excluded because the freeing of a page by slab shrinking depends on each slab's object population, making the cost model (i.e. scan:free) different from that of LRU. Also, not every shrinker accounts the pages it reclaims. This is a regression introduced by commit 6b4f7799c6a5 ("mm: vmscan: invoke slab shrinkers from shrink_zone()"). Signed-off-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx> --- mm/vmscan.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 947ab6f..8969f8e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2594,16 +2594,23 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) sc->nr_scanned - nr_scanned, node_lru_pages); + /* + * Record the subtree's reclaim efficiency. The reclaimed + * pages from slab is excluded here because the corresponding + * scanned pages is not accounted. Moreover, freeing a page + * by slab shrinking depends on each slab's object population, + * making the cost model (i.e. scan:free) different from that + * of LRU. + */ + vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, + sc->nr_scanned - nr_scanned, + sc->nr_reclaimed - nr_reclaimed); + if (reclaim_state) { sc->nr_reclaimed += reclaim_state->reclaimed_slab; reclaim_state->reclaimed_slab = 0; } - /* Record the subtree's reclaim efficiency */ - vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, - sc->nr_scanned - nr_scanned, - sc->nr_reclaimed - nr_reclaimed); - if (sc->nr_reclaimed - nr_reclaimed) reclaimable = true; -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>