From: Jan Kara <jack@suse.cz>
To: Richard Weinberger <richard@nod.at>
Cc: "Jan Kara" <jack@suse.cz>, "wuchi zero" <wuchi.zero@gmail.com>,
"Rafał Miłecki" <zajec5@gmail.com>, tj <tj@kernel.org>,
mszeredi <mszeredi@redhat.com>,
"sedat dilek" <sedat.dilek@gmail.com>, axboe <axboe@fb.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
torvalds <torvalds@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
linux-mtd <linux-mtd@lists.infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Different writeback timing since v5.14
Date: Wed, 2 Mar 2022 10:24:15 +0100 [thread overview]
Message-ID: <20220302092415.4sikhzup7sorhxgy@quack3.lan> (raw)
In-Reply-To: <719960584.100772.1646147154879.JavaMail.zimbra@nod.at>
On Tue 01-03-22 16:05:54, Richard Weinberger wrote:
> Jan,
>
> ----- Ursprüngliche Mail -----
> > Von: "Jan Kara" <jack@suse.cz>
> >> Is this expected?
> >> Just want to make sure that the said commit didn't uncover an UBIFS issue.
> >
> > Yes, I think it is expected. Likely the background threshold for UBIFS bdi
> > is very small (probably UBIFS is not used much for writeback compared to
> > other filesystems). Previously, we just used wb_stat() which returned 0
> > (PCP counter inexact value) and so background writeback didn't trigger. Now
> > we use wb_stat_sum() when threshold is small, get exact value of dirty
> > pages and decide to start background writeback.
>
> Thanks for the prompt reply!
>
> > The only thing is, whether it is really expected that the threshold for
> > UBIFS bdi is so small. You can check the values in
> > /sys/kernel/debug/bdi/<bdi>/stats.
>
> BdiDirtyThresh is indeed 0.
>
> BdiWriteback: 0 kB
> BdiReclaimable: 0 kB
> BdiDirtyThresh: 0 kB
> DirtyThresh: 772620 kB
> BackgroundThresh: 385836 kB
> BdiDirtied: 0 kB
> BdiWritten: 0 kB
> BdiWriteBandwidth: 102400 kBps
> b_dirty: 0
> b_io: 0
> b_more_io: 0
> b_dirty_time: 0
> bdi_list: 1
> state: 1
Yes, so this looks expected given the BDI wasn't active yet at all...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Richard Weinberger <richard@nod.at>
Cc: "Jan Kara" <jack@suse.cz>, "wuchi zero" <wuchi.zero@gmail.com>,
"Rafał Miłecki" <zajec5@gmail.com>, tj <tj@kernel.org>,
mszeredi <mszeredi@redhat.com>,
"sedat dilek" <sedat.dilek@gmail.com>, axboe <axboe@fb.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
torvalds <torvalds@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
linux-mtd <linux-mtd@lists.infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Different writeback timing since v5.14
Date: Wed, 2 Mar 2022 10:24:15 +0100 [thread overview]
Message-ID: <20220302092415.4sikhzup7sorhxgy@quack3.lan> (raw)
In-Reply-To: <719960584.100772.1646147154879.JavaMail.zimbra@nod.at>
On Tue 01-03-22 16:05:54, Richard Weinberger wrote:
> Jan,
>
> ----- Ursprüngliche Mail -----
> > Von: "Jan Kara" <jack@suse.cz>
> >> Is this expected?
> >> Just want to make sure that the said commit didn't uncover an UBIFS issue.
> >
> > Yes, I think it is expected. Likely the background threshold for UBIFS bdi
> > is very small (probably UBIFS is not used much for writeback compared to
> > other filesystems). Previously, we just used wb_stat() which returned 0
> > (PCP counter inexact value) and so background writeback didn't trigger. Now
> > we use wb_stat_sum() when threshold is small, get exact value of dirty
> > pages and decide to start background writeback.
>
> Thanks for the prompt reply!
>
> > The only thing is, whether it is really expected that the threshold for
> > UBIFS bdi is so small. You can check the values in
> > /sys/kernel/debug/bdi/<bdi>/stats.
>
> BdiDirtyThresh is indeed 0.
>
> BdiWriteback: 0 kB
> BdiReclaimable: 0 kB
> BdiDirtyThresh: 0 kB
> DirtyThresh: 772620 kB
> BackgroundThresh: 385836 kB
> BdiDirtied: 0 kB
> BdiWritten: 0 kB
> BdiWriteBandwidth: 102400 kBps
> b_dirty: 0
> b_io: 0
> b_more_io: 0
> b_dirty_time: 0
> bdi_list: 1
> state: 1
Yes, so this looks expected given the BDI wasn't active yet at all...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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Linux MTD discussion mailing list
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next prev parent reply other threads:[~2022-03-02 9:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-01 10:11 Different writeback timing since v5.14 Richard Weinberger
2022-03-01 10:11 ` Richard Weinberger
2022-03-01 10:32 ` Jan Kara
2022-03-01 10:32 ` Jan Kara
2022-03-01 15:05 ` Richard Weinberger
2022-03-01 15:05 ` Richard Weinberger
2022-03-02 9:24 ` Jan Kara [this message]
2022-03-02 9:24 ` Jan Kara
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