linux-kernel - [PATCH] mm/vmscan: when the swappiness is set to 0, memory swapping should be prohibited during the global reclaim process

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Message-ID: <CAN2Y7hxDdATNfb=R5J1as3pqA1RsP8c8LubC4QxojK5cJS9Q9w@mail.gmail.com>
Date: Thu, 27 Feb 2025 22:34:51 +0800
From: ying chen <yc1082463@...il.com>
To: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] mm/vmscan: when the swappiness is set to 0, memory swapping
 should be prohibited during the global reclaim process

When we use zram as swap disks, global reclaim may cause the memory in some
cgroups with memory.swappiness set to 0 to be swapped into zram. This memory
won't be swapped back immediately after the free memory increases. Instead,
it will continue to occupy the zram space, which may result in no available
zram space for the cgroups with swapping enabled. Therefore, I think that
when the vm.swappiness is set to 0, global reclaim should also refrain
from memory swapping, just like these cgroups.

Signed-off-by: yc1082463 <yc1082463@...il.com>
---
 mm/vmscan.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c767d71c43d7..bdbb0fc03412 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2426,14 +2426,7 @@ static void get_scan_count(struct lruvec
*lruvec, struct scan_control *sc,
                goto out;
        }

-       /*
-        * Global reclaim will swap to prevent OOM even with no
-        * swappiness, but memcg users want to use this knob to
-        * disable swapping for individual groups completely when
-        * using the memory controller's swap limit feature would be
-        * too expensive.
-        */
-       if (cgroup_reclaim(sc) && !swappiness) {
+       if (!swappiness) {
                scan_balance = SCAN_FILE;
                goto out;
        }
--
2.34.1