Commit 57f29762 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

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.

But 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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reported-by: default avatarRik van Riel <riel@surriel.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fcc00621

mm/vmscan.c

+3 −0
Original line number Diff line number Diff line
@@ -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);