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From: Zheng Liu <gnehzuil.liu@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 0/6 RFC] Mapping range lock
Date: Mon, 4 Feb 2013 17:29:06 +0800	[thread overview]
Message-ID: <20130204092906.GA7503@gmail.com> (raw)
In-Reply-To: <20130131160757.06d7f1c2.akpm@linux-foundation.org>

On Thu, Jan 31, 2013 at 04:07:57PM -0800, Andrew Morton wrote:
[snip]
> > c) i_mutex doesn't allow any paralellism of operations using it and some
> >    filesystems workaround this for specific cases (e.g. DIO reads). Using
> >    range locking allows for concurrent operations (e.g. writes, DIO) on
> >    different parts of the file. Of course, range locking itself isn't
> >    enough to make the parallelism possible. Filesystems still have to
> >    somehow deal with the concurrency when manipulating inode allocation
> >    data. But the range locking at least provides a common VFS mechanism for
> >    serialization VFS itself needs and it's upto each filesystem to
> >    serialize more if it needs to.
> 
> That would be useful to end-users, but I'm having trouble predicting
> *how* useful.

Hello Andrew,

I believe this would be useful for the end-user, at least for dio user, e.g.
database.  Now when we want to issue a direct io, i_mutex will serialize
concurrent reader/writer.  Some filesystems (xfs and ext4) try not to take
this locking in some conditions to improve the performance, especially for the
latency, because we don't need to wait on this locking.  But there are still
some cases that need to take it.  So range locking can make us reduce the
contention as far as possible.

Regards,
						- Zheng

WARNING: multiple messages have this Message-ID (diff)
From: Zheng Liu <gnehzuil.liu@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 0/6 RFC] Mapping range lock
Date: Mon, 4 Feb 2013 17:29:06 +0800	[thread overview]
Message-ID: <20130204092906.GA7503@gmail.com> (raw)
In-Reply-To: <20130131160757.06d7f1c2.akpm@linux-foundation.org>

On Thu, Jan 31, 2013 at 04:07:57PM -0800, Andrew Morton wrote:
[snip]
> > c) i_mutex doesn't allow any paralellism of operations using it and some
> >    filesystems workaround this for specific cases (e.g. DIO reads). Using
> >    range locking allows for concurrent operations (e.g. writes, DIO) on
> >    different parts of the file. Of course, range locking itself isn't
> >    enough to make the parallelism possible. Filesystems still have to
> >    somehow deal with the concurrency when manipulating inode allocation
> >    data. But the range locking at least provides a common VFS mechanism for
> >    serialization VFS itself needs and it's upto each filesystem to
> >    serialize more if it needs to.
> 
> That would be useful to end-users, but I'm having trouble predicting
> *how* useful.

Hello Andrew,

I believe this would be useful for the end-user, at least for dio user, e.g.
database.  Now when we want to issue a direct io, i_mutex will serialize
concurrent reader/writer.  Some filesystems (xfs and ext4) try not to take
this locking in some conditions to improve the performance, especially for the
latency, because we don't need to wait on this locking.  But there are still
some cases that need to take it.  So range locking can make us reduce the
contention as far as possible.

Regards,
						- Zheng

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  reply	other threads:[~2013-02-04  9:14 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-31 21:49 [PATCH 0/6 RFC] Mapping range lock Jan Kara
2013-01-31 21:49 ` Jan Kara
2013-01-31 21:49 ` [PATCH 1/6] lib: Implement range locks Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-01-31 23:57   ` Andrew Morton
2013-01-31 23:57     ` Andrew Morton
2013-02-04 16:41     ` Jan Kara
2013-02-04 16:41       ` Jan Kara
2013-02-11  5:42   ` Michel Lespinasse
2013-02-11  5:42     ` Michel Lespinasse
2013-02-11 10:27     ` Jan Kara
2013-02-11 10:27       ` Jan Kara
2013-02-11 11:03       ` Michel Lespinasse
2013-02-11 11:03         ` Michel Lespinasse
2013-02-11 12:58         ` Jan Kara
2013-02-11 12:58           ` Jan Kara
2013-01-31 21:49 ` [PATCH 2/6] fs: Take mapping lock in generic read paths Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-01-31 23:59   ` Andrew Morton
2013-01-31 23:59     ` Andrew Morton
2013-02-04 12:47     ` Jan Kara
2013-02-04 12:47       ` Jan Kara
2013-02-08 14:59       ` Jan Kara
2013-02-08 14:59         ` Jan Kara
2013-01-31 21:49 ` [PATCH 3/6] fs: Provide function to take mapping lock in buffered write path Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-01-31 21:49 ` [PATCH 4/6] fs: Don't call dio_cleanup() before submitting all bios Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-01-31 21:49 ` [PATCH 5/6] fs: Take mapping lock during direct IO Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-01-31 21:49 ` [PATCH 6/6] ext3: Convert ext3 to use mapping lock Jan Kara
2013-01-31 21:49   ` Jan Kara
2013-02-01  0:07 ` [PATCH 0/6 RFC] Mapping range lock Andrew Morton
2013-02-01  0:07   ` Andrew Morton
2013-02-04  9:29   ` Zheng Liu [this message]
2013-02-04  9:29     ` Zheng Liu
2013-02-04 12:38   ` Jan Kara
2013-02-04 12:38     ` Jan Kara
2013-02-05 23:25     ` Dave Chinner
2013-02-05 23:25       ` Dave Chinner
2013-02-06 19:25       ` Jan Kara
2013-02-06 19:25         ` Jan Kara
2013-02-07  2:43         ` Dave Chinner
2013-02-07  2:43           ` Dave Chinner
2013-02-07 11:06           ` Jan Kara
2013-02-07 11:06             ` Jan Kara

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