From: Kemeng Shi <shikemeng@huaweicloud.com>
To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/7] fs/writeback: avoid to writeback non-expired inode in kupdate writeback
Date: Fri, 9 Feb 2024 01:20:18 +0800 [thread overview]
Message-ID: <20240208172024.23625-2-shikemeng@huaweicloud.com> (raw)
In-Reply-To: <20240208172024.23625-1-shikemeng@huaweicloud.com>
In kupdate writeback, only expired inode (have been dirty for longer than
dirty_expire_interval) is supposed to be written back. However, kupdate
writeback will writeback non-expired inode left in b_io or b_more_io from
last wb_writeback. As a result, writeback will keep being triggered
unexpected when we keep dirtying pages even dirty memory is under
threshold and inode is not expired. To be more specific:
Assume dirty background threshold is > 1G and dirty_expire_centisecs is
> 60s. When we running fio -size=1G -invalidate=0 -ioengine=libaio
--time_based -runtime=60... (keep dirtying), the writeback will keep
being triggered as following:
wb_workfn
wb_do_writeback
wb_check_background_flush
/*
* Wb dirty background threshold starts at 0 if device was idle and
* grows up when bandwidth of wb is updated. So a background
* writeback is triggered.
*/
wb_over_bg_thresh
/*
* Dirtied inode will be written back and added to b_more_io list
* after slice used up (because we keep dirtying the inode).
*/
wb_writeback
Writeback is triggered per dirty_writeback_centisecs as following:
wb_workfn
wb_do_writeback
wb_check_old_data_flush
/*
* Write back inode left in b_io and b_more_io from last wb_writeback
* even the inode is non-expired and it will be added to b_more_io
* again as slice will be used up (because we keep dirtying the
* inode)
*/
wb_writeback
Fix this by moving non-expired inode in io list from last wb_writeback to
dirty list in kudpate writeback.
Test as following:
/* make it more easier to observe the issue */
echo 300000 > /proc/sys/vm/dirty_expire_centisecs
echo 100 > /proc/sys/vm/dirty_writeback_centisecs
/* create a idle device */
mkfs.ext4 -F /dev/vdb
mount /dev/vdb /bdi1/
/* run buffer write with fio */
fio -name test -filename=/bdi1/file -size=800M -ioengine=libaio -bs=4K \
-iodepth=1 -rw=write -direct=0 --time_based -runtime=60 -invalidate=0
Result before fix (run three tests):
1360MB/s
1329MB/s
1455MB/s
Result after fix (run three tests);
790MB/s
1820MB/s
1804MB/s
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
fs/fs-writeback.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5ab1aaf805f7..a9a918972719 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2046,6 +2046,23 @@ static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
return nr_pages - work.nr_pages;
}
+static void filter_expired_io(struct bdi_writeback *wb)
+{
+ struct inode *inode, *tmp;
+ unsigned long expired_jiffies = jiffies -
+ msecs_to_jiffies(dirty_expire_interval * 10);
+
+ spin_lock(&wb->list_lock);
+ list_for_each_entry_safe(inode, tmp, &wb->b_io, i_io_list)
+ if (inode_dirtied_after(inode, expired_jiffies))
+ redirty_tail(inode, wb);
+
+ list_for_each_entry_safe(inode, tmp, &wb->b_more_io, i_io_list)
+ if (inode_dirtied_after(inode, expired_jiffies))
+ redirty_tail(inode, wb);
+ spin_unlock(&wb->list_lock);
+}
+
/*
* Explicit flushing or periodic writeback of "old" data.
*
@@ -2070,6 +2087,9 @@ static long wb_writeback(struct bdi_writeback *wb,
long progress;
struct blk_plug plug;
+ if (work->for_kupdate)
+ filter_expired_io(wb);
+
blk_start_plug(&plug);
for (;;) {
/*
--
2.30.0
next prev parent reply other threads:[~2024-02-08 9:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-08 17:20 [PATCH 0/7] Fixes and cleanups to fs-writeback Kemeng Shi
2024-02-08 17:20 ` Kemeng Shi [this message]
2024-02-08 18:29 ` [PATCH 1/7] fs/writeback: avoid to writeback non-expired inode in kupdate writeback Tim Chen
2024-02-18 2:01 ` Kemeng Shi
2024-02-28 1:46 ` Kemeng Shi
2024-02-23 13:42 ` Jan Kara
2024-02-26 11:47 ` Kemeng Shi
2024-02-08 17:20 ` [PATCH 2/7] fs/writeback: bail out if there is no more inodes for IO and queued once Kemeng Shi
2024-02-08 19:21 ` Tim Chen
2024-02-18 2:11 ` Kemeng Shi
2024-02-23 13:49 ` Jan Kara
2024-02-08 17:20 ` [PATCH 3/7] fs/writeback: remove unused parameter wb of finish_writeback_work Kemeng Shi
2024-02-08 19:26 ` Tim Chen
2024-02-23 13:49 ` Jan Kara
2024-02-08 17:20 ` [PATCH 4/7] fs/writeback: remove unneeded check in writeback_single_inode Kemeng Shi
2024-02-08 19:34 ` Tim Chen
2024-02-10 0:46 ` Dave Chinner
2024-02-18 2:37 ` Kemeng Shi
2024-02-08 17:20 ` [PATCH 5/7] fs/writeback: only calculate dirtied_before when b_io is empty Kemeng Shi
2024-02-23 13:58 ` Jan Kara
2024-02-26 11:50 ` Kemeng Shi
2024-02-08 17:20 ` [PATCH 6/7] fs/writeback: correct comment of __wakeup_flusher_threads_bdi Kemeng Shi
2024-02-23 13:59 ` Jan Kara
2024-02-08 17:20 ` [PATCH 7/7] fs/writeback: remove unnecessary return in writeback_inodes_sb Kemeng Shi
2024-02-23 13:59 ` Jan Kara
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