From: Joseph Qi <joseph.qi@linux.alibaba.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>,
Ext4 Developers List <linux-ext4@vger.kernel.org>
Cc: Liu Bo <bo.liu@linux.alibaba.com>,
Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Subject: Re: Discussion: is it time to remove dioread_nolock?
Date: Fri, 27 Dec 2019 21:10:26 +0800 [thread overview]
Message-ID: <dc324872-9720-0590-5501-043c84d9ddc6@linux.alibaba.com> (raw)
In-Reply-To: <20191226153118.GA17237@mit.edu>
Hi Ted,
After applying Ritesh's patches, from my test result, there is no
obvious performance difference between default mount options and
with dioread_lock (delalloc or nodelalloc).
I'm not sure if dioread_nolock was used for other purpose in the
scenario reported by Bo Liu. Maybe Xiaoguang could give some inputs.
Thanks,
Joseph
On 19/12/26 23:31, Theodore Y. Ts'o wrote:
> With inclusion of Ritesh's inode lock scalability patches[1], the
> traditional performance reasons for dioread_nolock --- namely,
> removing the need to take an exclusive lock for Direct I/O read
> operations --- has been removed.
>
> [1] https://lore.kernel.org/r/20191212055557.11151-1-riteshh@linux.ibm.com
>
> So... is it time to remove the code which supports dioread_nolock?
> Doing so would simplify the code base, and reduce the test matrix.
> This would also make it easier to restructure the write path when
> allocating blocks so that the extent tree is updated after writing out
> the data blocks, by clearing away the underbrush of dioread nolock
> first.
>
> If we do this, we'd leave the dioread_nolock mount option for
> backwards compatibility, but it would be a no-op and not actually do
> anything.
>
> Any objections before I look into ripping out dioread_nolock?
>
> The one possible concern that I considered was for Alibaba, which was
> doing something interesting with dioread_nolock plus nodelalloc. But
> looking at Liu Bo's explanation[2], I believe that their workload
> would be satisfied simply by using the standard ext4 mount options
> (that is, the default mode has the performance benefits when doing
> parallel DIO reads, and so the need for nodelalloc to mitigate the
> tail latency concerns which Alibaba was seeing in their workload would
> not be needed). Could Liu or someone from Alibaba confirm, perhaps
> with some benchmarks using their workload?
>
> [2] https://lore.kernel.org/linux-ext4/20181121013035.ab4xp7evjyschecy@US-160370MP2.local/
>
> - Ted
>
next prev parent reply other threads:[~2019-12-27 13:10 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-26 15:31 Discussion: is it time to remove dioread_nolock? Theodore Y. Ts'o
2019-12-27 13:10 ` Joseph Qi [this message]
2019-12-29 15:03 ` Xiaoguang Wang
2020-01-06 12:24 ` Ritesh Harjani
2020-01-07 0:43 ` Theodore Y. Ts'o
2020-01-07 8:22 ` Jan Kara
2020-01-07 17:11 ` Theodore Y. Ts'o
2020-01-07 17:22 ` Jan Kara
2020-01-08 10:45 ` Ritesh Harjani
2020-01-08 17:42 ` Theodore Y. Ts'o
2020-01-09 9:21 ` Ritesh Harjani
2020-01-09 16:38 ` Theodore Y. Ts'o
2020-01-14 23:30 ` Ritesh Harjani
2020-01-15 16:48 ` Theodore Y. Ts'o
2020-01-16 9:46 ` Ritesh Harjani
2020-01-09 12:34 ` Jan Kara
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