[patch 08/10] mm: vmscan: fix missing psi annotation for node_reclaim()

[Andrew Morton <akpm@linux-foundation.org>]

From: Johannes Weiner <hannes@cmpxchg.org>
Subject: mm: vmscan: fix missing psi annotation for node_reclaim()

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@viggo.jf.intel.com/)
could soon make this a more common codepath again.

Link: https://lkml.kernel.org/r/20210818152457.35846-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/vmscan.c~mm-vmscan-fix-missing-psi-annotation-for-node_reclaim
+++ a/mm/vmscan.c
@@ -4424,11 +4424,13 @@ static int __node_reclaim(struct pglist_
 		.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_
 	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);
 
_