In a debugging session the other day, Rik noticed that node_reclaim() was missing memstall annotations. This means we'll miss pressure and lost productivity resulting from reclaim on an overloaded local NUMA node when vm.zone_reclaim_mode is enabled. There haven't been any reports, but that's likely because vm.zone_reclaim_mode hasn't been a commonly used feature recently, and the intersection between such setups and psi users is probably nil. Although, secondary memory such as CXL-connected DIMMS, persistent memory etc. and the page demotion patches that handle them (https://lore.kernel.org/lkml/20210401183216.443C4443@xxxxxxxxxxxxxxxxxx/) could soon make this a more common codepath again. Reported-by: Rik van Riel <riel@xxxxxxxxxxx> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> --- mm/vmscan.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 701106e1829c..8ec4412c6116 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4424,11 +4424,13 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in .may_swap = 1, .reclaim_idx = gfp_zone(gfp_mask), }; + unsigned long pflags; trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order, sc.gfp_mask); cond_resched(); + psi_memstall_enter(&pflags); fs_reclaim_acquire(sc.gfp_mask); /* * We need to be able to allocate from the reserves for RECLAIM_UNMAP @@ -4453,6 +4455,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in current->flags &= ~PF_SWAPWRITE; memalloc_noreclaim_restore(noreclaim_flag); fs_reclaim_release(sc.gfp_mask); + psi_memstall_leave(&pflags); trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed); -- 2.32.0
