linux-kernel - [PATCH] fs: drop_caches: draining pages before dropping caches

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Message-ID: <20230630092203.16080-1-andrew.yang@mediatek.com>
Date:   Fri, 30 Jun 2023 17:22:02 +0800
From:   Andrew Yang <andrew.yang@...iatek.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
CC:     <wsd_upstream@...iatek.com>, <casper.li@...iatek.com>,
        Andrew Yang <andrew.yang@...iatek.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH] fs: drop_caches: draining pages before dropping caches

We expect a file page access after dropping caches should be a major
fault, but sometimes it's still a minor fault. That's because a file
page can't be dropped if it's in a per-cpu pagevec. Draining all pages
from per-cpu pagevec to lru list before trying to drop caches.

Signed-off-by: Andrew Yang <andrew.yang@...iatek.com>
---
 fs/drop_caches.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index e619c31b6bd9..b9575957a7c2 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -10,6 +10,7 @@
 #include <linux/writeback.h>
 #include <linux/sysctl.h>
 #include <linux/gfp.h>
+#include <linux/swap.h>
 #include "internal.h"
 
 /* A global variable is a bit ugly, but it keeps the code simple */
@@ -59,6 +60,7 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
 		static int stfu;
 
 		if (sysctl_drop_caches & 1) {
+			lru_add_drain_all();
 			iterate_supers(drop_pagecache_sb, NULL);
 			count_vm_event(DROP_PAGECACHE);
 		}
-- 
2.18.0