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From:   Zhaoyang Huang <huangzhaoyang@gmail.com>
To:     Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: [RFC PATCH] mm: bail out from psi memstall when cond_resched
Date:   Wed, 18 Nov 2020 11:22:56 +0800
Message-Id: <1605669776-24242-1-git-send-email-zhaoyang.huang@unisoc.com>
Precedence: bulk

Memory reclaiming will run as several seconds in memory constraint system, which
will be deemed as heavy memstall. Have the memory reclaim be more presiced by
bailing out when cond_resched

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 mm/vmscan.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a815f73..a083c85 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -316,6 +316,15 @@ static inline bool memcg_congested(struct pglist_data *pgdat,
 }
 #endif
 
+static inline void psi_cond_resched(void)
+{
+	unsigned long *flags;
+
+	if (current->flags & PF_MEMSTALL)
+		psi_memstall_leave(&flags);
+	cond_resched();
+	psi_memstall_enter(&flags);
+}
 /*
  * This misses isolated pages which are not accounted for to save counters.
  * As the data only determines if reclaim or compaction continues, it is
@@ -557,7 +566,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 		total_scan -= shrinkctl->nr_scanned;
 		scanned += shrinkctl->nr_scanned;
 
-		cond_resched();
+		psi_cond_resched();
 	}
 
 	if (next_deferred >= scanned)
@@ -714,7 +723,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 
 	up_read(&shrinker_rwsem);
 out:
-	cond_resched();
+	psi_cond_resched();
 	return freed;
 }
 
@@ -1109,7 +1118,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 	unsigned nr_reclaimed = 0;
 
 	memset(stat, 0, sizeof(*stat));
-	cond_resched();
+	psi_cond_resched();
 
 	while (!list_empty(page_list)) {
 		struct address_space *mapping;
@@ -1118,7 +1127,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		enum page_references references = PAGEREF_RECLAIM_CLEAN;
 		bool dirty, writeback;
 
-		cond_resched();
+		psi_cond_resched();
 
 		page = lru_to_page(page_list);
 		list_del(&page->lru);
@@ -2084,7 +2093,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	spin_unlock_irq(&pgdat->lru_lock);
 
 	while (!list_empty(&l_hold)) {
-		cond_resched();
+		psi_cond_resched();
 		page = lru_to_page(&l_hold);
 		list_del(&page->lru);
 
@@ -2500,7 +2509,7 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
 			}
 		}
 
-		cond_resched();
+		psi_cond_resched();
 
 		if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
 			continue;
@@ -4149,7 +4158,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 		.reclaim_idx = gfp_zone(gfp_mask),
 	};
 
-	cond_resched();
+	psi_cond_resched();
 	fs_reclaim_acquire(sc.gfp_mask);
 	/*
 	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
-- 
1.9.1