linux-ext4 - Re: [RFC] ext4: Don't send extra barrier during fsync if there are no dirty pages.

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Message-ID: <4C5A1FDC.3010700@redhat.com>
Date:	Thu, 05 Aug 2010 05:20:12 +0300
From:	Avi Kivity <avi@...hat.com>
To:	"Ted Ts'o" <tytso@....edu>, Christoph Hellwig <hch@...radead.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	Mingming Cao <cmm@...ibm.com>, djwong@...ibm.com,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Keith Mannthey <kmannth@...ibm.com>,
	Mingming Cao <mcao@...ibm.com>
Subject: Re: [RFC] ext4: Don't send extra barrier during fsync if there are
 no dirty pages.

  On 08/05/2010 02:32 AM, Ted Ts'o wrote:
> On Tue, Aug 03, 2010 at 04:24:49PM +0300, Avi Kivity wrote:
>>   On 06/30/2010 03:48 PM, tytso@....edu wrote:
>>> I wonder if it's worthwhile to think about a new system call which
>>> allows users to provide an array of fd's which are collectively should
>>> be fsync'ed out at the same time.  Otherwise, we end up issuing
>>> multiple barrier operations in cases where the application needs to
>>> do:
>>>
>>> 	fsync(control_fd);
>>> 	fsync(data_fd);
>>>
>> The system call exists, it's called io_submit().
> Um, not the same thing at all.

Why not?  To be clear, I'm talking about an io_submit() with multiple 
IO_CMD_FSYNC requests, with a kernel implementation that is able to 
batch these requests.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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