From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Sergey Meirovich <rathamahata@gmail.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Gluk <git.user@gmail.com>
Subject: Re: Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage.
Date: Tue, 7 Jan 2014 07:58:30 -0800 [thread overview]
Message-ID: <20140107155830.GA28395@infradead.org> (raw)
In-Reply-To: <20140106201032.GA13491@quack.suse.cz>
On Mon, Jan 06, 2014 at 09:10:32PM +0100, Jan Kara wrote:
> This is likely a problem of Linux direct IO implementation. The thing is
> that in Linux when you are doing appending direct IO (i.e., direct IO which
> changes file size), the IO is performed synchronously so that we have our
> life simpler with inode size update etc. (and frankly our current locking
> rules make inode size update on IO completion almost impossible). Since
> appending direct IO isn't very common, we seem to get away with this
> simplification just fine...
Shouldn't be too much of a problem at least for XFS and maybe even ext4
with the workqueue based I/O end handler. For XFS we protect size
updates by the ilock which we already taken in that handler, not sure
what ext4 would do there.
next prev parent reply other threads:[~2014-01-07 15:58 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-06 9:38 Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage Sergey Meirovich
2014-01-06 20:10 ` Jan Kara
2014-01-07 9:13 ` Sergey Meirovich
2014-01-07 15:58 ` Christoph Hellwig [this message]
2014-01-07 18:37 ` Sergey Meirovich
2014-01-08 14:03 ` Christoph Hellwig
2014-01-08 14:43 ` Sergey Meirovich
2014-01-08 15:26 ` Christoph Hellwig
2014-01-08 17:30 ` Sergey Meirovich
2014-01-08 20:55 ` Jan Kara
2014-01-09 10:11 ` Sergey Meirovich
2014-01-10 9:36 ` Jan Kara
2014-01-10 10:36 ` Sergey Meirovich
2014-01-10 10:48 ` Jan Kara
2014-01-10 14:32 ` Sergey Meirovich
2014-01-10 18:14 ` Sergey Meirovich
2014-01-14 13:30 ` Sergey Meirovich
2014-01-14 13:30 ` Sergey Meirovich
2014-01-15 22:07 ` Dave Chinner
2014-01-15 22:07 ` Dave Chinner
2014-01-20 13:58 ` Christoph Hellwig
2014-01-20 13:58 ` Christoph Hellwig
2014-01-20 22:18 ` Dave Chinner
2014-01-20 22:18 ` Dave Chinner
2014-01-08 1:17 ` Jan Kara
2014-01-08 14:03 ` Christoph Hellwig
2014-01-07 20:57 ` James Smart
2014-01-08 13:57 ` Sergey Meirovich
2014-01-09 19:54 ` Douglas Gilbert
2014-01-09 21:26 ` Sergey Meirovich
2014-01-09 21:43 ` Sergey Meirovich
-- strict thread matches above, loose matches on Subject: below --
2014-01-06 13:16 Sergey Meirovich
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