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smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4TkxS82TBZz4f3jsq; Wed, 28 Feb 2024 09:23:04 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 8CDA31A0572; Wed, 28 Feb 2024 09:23:09 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP1 (Coremail) with SMTP id cCh0CgDX8gv7it5lqQx6FQ--.57137S3; Wed, 28 Feb 2024 09:23:09 +0800 (CST) From: Kemeng Shi To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, tim.c.chen@linux.intel.com Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/6] fs/writeback: avoid to writeback non-expired inode in kupdate writeback Date: Wed, 28 Feb 2024 17:19:53 +0800 Message-Id: <20240228091958.288260-2-shikemeng@huaweicloud.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20240228091958.288260-1-shikemeng@huaweicloud.com> References: <20240228091958.288260-1-shikemeng@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgDX8gv7it5lqQx6FQ--.57137S3 X-Coremail-Antispam: 1UD129KBjvJXoWxZF4rJF1xuw4xXF4kJr4rGrg_yoWrCF1xpF WUGr15tr4qvFWxWrnaka429r13tay8AF47Jr1xWay2q3WjqFWUtFyUuFy2yr18Jr93WrWS qF4vvryxAr40yaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUB0b4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M280x2IEY4vEnII2IxkI6r1a6r45M2 8IrcIa0xkI8VA2jI8067AKxVWUGwA2048vs2IY020Ec7CjxVAFwI0_JFI_Gr1l8cAvFVAK 0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVW7JVWDJwA2z4 x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l 84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I 8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AK xVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41l42xK82IYc2Ij64 vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8G jcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE2I x0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK 8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I 0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxUsgyZUUUUU X-CM-SenderInfo: 5vklyvpphqwq5kxd4v5lfo033gof0z/ X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1792103983501681116 X-GMAIL-MSGID: 1792103983501681116 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 to dirty list instead of more io list for kupdate writeback in requeue_inode. 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 Fio result before fix (run three tests): 1360MB/s 1329MB/s 1455MB/s Fio result after fix (run three tests): 1737MB/s 1729MB/s 1789MB/s Writeback for non-expired inode is gone as expeted. Observe this with trace writeback_start and writeback_written as following: echo 1 > /sys/kernel/debug/tracing/events/writeback/writeback_start/enab echo 1 > /sys/kernel/debug/tracing/events/writeback/writeback_written/enable cat /sys/kernel/tracing/trace_pipe Signed-off-by: Kemeng Shi --- fs/fs-writeback.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 5ab1aaf805f7..4e6166e07eaf 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1561,7 +1561,8 @@ static void inode_sleep_on_writeback(struct inode *inode) * thread's back can have unexpected consequences. */ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, - struct writeback_control *wbc) + struct writeback_control *wbc, + unsigned long dirtied_before) { if (inode->i_state & I_FREEING) return; @@ -1594,7 +1595,8 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, * We didn't write back all the pages. nfs_writepages() * sometimes bales out without doing anything. */ - if (wbc->nr_to_write <= 0) { + if (wbc->nr_to_write <= 0 && + !inode_dirtied_after(inode, dirtied_before)) { /* Slice used up. Queue for next turn. */ requeue_io(inode, wb); } else { @@ -1862,6 +1864,11 @@ static long writeback_sb_inodes(struct super_block *sb, unsigned long start_time = jiffies; long write_chunk; long total_wrote = 0; /* count both pages and inodes */ + unsigned long dirtied_before = jiffies; + + if (work->for_kupdate) + dirtied_before = jiffies - + msecs_to_jiffies(dirty_expire_interval * 10); while (!list_empty(&wb->b_io)) { struct inode *inode = wb_inode(wb->b_io.prev); @@ -1967,7 +1974,7 @@ static long writeback_sb_inodes(struct super_block *sb, spin_lock(&inode->i_lock); if (!(inode->i_state & I_DIRTY_ALL)) total_wrote++; - requeue_inode(inode, tmp_wb, &wbc); + requeue_inode(inode, tmp_wb, &wbc, dirtied_before); inode_sync_complete(inode); spin_unlock(&inode->i_lock);