delayacct: add memory reclaim delay in get_page_from_freelist

The current memory reclaim delay statistics only count the direct memory
reclaim of the task in do_try_to_free_pages().  In systems with NUMA open,
some tasks occasionally experience slower response times, but the total
count of reclaim does not increase, using ftrace can show that
node_reclaim has occurred.

The memory reclaim occurring in get_page_from_freelist() is also due to
heavy memory load.  To get the impact of tasks in memory reclaim, this
patch adds the statistics of the memory reclaim delay statistics for
__node_reclaim().

Link: https://lkml.kernel.org/r/181C946095F0252B+7cc60eca-1abf-4502-aad3-ffd8ef89d910@ex.bilibili.comSigned-off-by: Wen Yu Li <wenyuli@ex.bilibili.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: <wangyun@bilibili.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -7326,6 +7326,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 
 	cond_resched();
 	psi_memstall_enter(&pflags);
+	delayacct_freepages_start();
 	fs_reclaim_acquire(sc.gfp_mask);
 	/*
 	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
@@ -7348,6 +7349,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 	memalloc_noreclaim_restore(noreclaim_flag);
 	fs_reclaim_release(sc.gfp_mask);
 	psi_memstall_leave(&pflags);
+	delayacct_freepages_end();
 
 	trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);