From a76cf1a474d7dbcd9336b5f5afb0162baa142cf0 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Fri, 16 Nov 2018 15:08:18 -0800 Subject: [PATCH] mm: don't reclaim inodes with many attached pages Spock reported that commit 172b06c32b94 ("mm: slowly shrink slabs with a relatively small number of objects") leads to a regression on his setup: periodically the majority of the pagecache is evicted without an obvious reason, while before the change the amount of free memory was balancing around the watermark. The reason behind is that the mentioned above change created some minimal background pressure on the inode cache. The problem is that if an inode is considered to be reclaimed, all belonging pagecache page are stripped, no matter how many of them are there. So, if a huge multi-gigabyte file is cached in the memory, and the goal is to reclaim only few slab objects (unused inodes), we still can eventually evict all gigabytes of the pagecache at once. The workload described by Spock has few large non-mapped files in the pagecache, so it's especially noticeable. To solve the problem let's postpone the reclaim of inodes, which have more than 1 attached page. Let's wait until the pagecache pages will be evicted naturally by scanning the corresponding LRU lists, and only then reclaim the inode structure. Link: http://lkml.kernel.org/r/20181023164302.20436-1-guro@fb.com Signed-off-by: Roman Gushchin Reported-by: Spock Tested-by: Spock Reviewed-by: Andrew Morton Cc: Michal Hocko Cc: Rik van Riel Cc: Randy Dunlap Cc: [4.19.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/inode.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 9e198f00b64c..35d2108d567c 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -730,8 +730,11 @@ static enum lru_status inode_lru_isolate(struct list_head *item, return LRU_REMOVED; } - /* recently referenced inodes get one more pass */ - if (inode->i_state & I_REFERENCED) { + /* + * Recently referenced inodes and inodes with many attached pages + * get one more pass. + */ + if (inode->i_state & I_REFERENCED || inode->i_data.nrpages > 1) { inode->i_state &= ~I_REFERENCED; spin_unlock(&inode->i_lock); return LRU_ROTATE;