linux-kernel - [RFC PATCH v1 11/11] mm: Wakeup kswapd if toptier memory need soft reclaim

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Date:   Mon,  5 Apr 2021 10:08:35 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Michal Hocko <mhocko@...e.cz>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Ying Huang <ying.huang@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 11/11] mm: Wakeup kswapd if toptier memory need soft reclaim

Detect during page allocation whether free toptier memory is low.
If so, wake up kswapd to reclaim memory from those mem cgroups
that have exceeded their limit.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 include/linux/mmzone.h | 3 +++
 mm/page_alloc.c        | 2 ++
 mm/vmscan.c            | 2 +-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 789319dffe1c..3603948e95cc 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -886,6 +886,8 @@ bool zone_watermark_ok(struct zone *z, unsigned int order,
 		unsigned int alloc_flags);
 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
 		unsigned long mark, int highest_zoneidx);
+bool pgdat_toptier_balanced(pg_data_t *pgdat, int order, int classzone_idx);
+
 /*
  * Memory initialization context, use to differentiate memory added by
  * the platform statically or via memory hotplug interface.
@@ -1466,5 +1468,6 @@ void sparse_init(void);
 #endif
 
 #endif /* !__GENERATING_BOUNDS.H */
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _LINUX_MMZONE_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 91212a837d8e..ca8aa789a967 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3519,6 +3519,8 @@ struct page *rmqueue(struct zone *preferred_zone,
 	if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
 		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
+	} else if (!pgdat_toptier_balanced(zone->zone_pgdat, order, zone_idx(zone))) {
+		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
 	}
 
 	VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 270880c8baef..8fe709e3f5e4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3625,7 +3625,7 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
 	return false;
 }
 
-static bool pgdat_toptier_balanced(pg_data_t *pgdat, int order, int classzone_idx)
+bool pgdat_toptier_balanced(pg_data_t *pgdat, int order, int classzone_idx)
 {
 	int i;
 	unsigned long mark;
-- 
2.20.1