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Date:   Tue, 1 Mar 2022 11:11:57 +0100 (CET)
From:   Richard Weinberger <richard@nod.at>
To:     wuchi.zero@gmail.com
Cc:     =?utf-8?Q?Rafa=C5=82_Mi=C5=82ecki?= <zajec5@gmail.com>,
        jack@suse.cz, tj@kernel.org, mszeredi@redhat.com,
        sedat.dilek@gmail.com, axboe@fb.com, akpm@linux-foundation.org,
        torvalds@linux-foundation.org, linux-mm <linux-mm@kvack.org>,
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        linux-kernel <linux-kernel@vger.kernel.org>
Message-ID: <2104629126.100059.1646129517209.JavaMail.zimbra@nod.at>
Subject: Different writeback timing since v5.14
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Thread-Topic: Different writeback timing since v5.14
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Hi!

Rafał and I discovered that page writeback on UBIFS behaves different since v5.14.
When a simple write, such as "echo foo > /mnt/ubibfs/bar.txt", happens it takes
a few seconds until writeback calls ubifs_writepage().

Before commit ab19939a6a50 ("mm/page-writeback: Fix performance when BDI's share of ratio is 0.")
it was 30 seconds (vm.dirty_expire_centisecs), after this change it happens after 5 seconds
(vm.dirty_writeback_centisecs).

Is this expected?
Just want to make sure that the said commit didn't uncover an UBIFS issue.

Thanks,
//richard