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Re: A huge latency in ext4 and xfs because of stable page write

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: A huge latency in ext4 and xfs because of stable page write
From: Zheng Liu <gnehzuil.liu@xxxxxxxxx>
Date: Wed, 12 Dec 2012 13:13:32 +0800
Cc: linux-ext4@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, tytso@xxxxxxx, hch@xxxxxxxxxxxxx, darrick.wong@xxxxxxxxxx
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In-reply-to: <20121212044948.GW16353@dastard>
Mail-followup-to: Dave Chinner <david@xxxxxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, tytso@xxxxxxx, hch@xxxxxxxxxxxxx, darrick.wong@xxxxxxxxxx
References: <20121211084520.GA13277@xxxxxxxxx> <20121211111707.GU15784@dastard> <20121212041803.GA29427@xxxxxxxxx> <20121212044948.GW16353@dastard>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Dec 12, 2012 at 03:49:49PM +1100, Dave Chinner wrote:
[cut...]
> > > > Hence, I wonder whether or not we could revert stable page write 
> > > > temporarily.
> > > > After it is improved, we could add it back again.
> > > 
> > > The plan is to turn it off for filesystems/devices that don't
> > > require it. That list of devices will grow in future, so you
> > > probably should plan to handle latencies in the application
> > > properly...
> > 
> > I wonder whether we can provide a sysctl to turn on/off stable page
> > write.  At least we need to give sysadmin an opportunity to control it.
> 
> That's already been considered and discarded because turning off
> stable pages on devices that require it will cause validation or
> data corruption problems. The discussion was for these patches (and
> I think a followup series as well):
> 
> http://www.spinics.net/lists/linux-fsdevel/msg59421.html

Thanks for pointing out.  So now it seems that only I can do is to
present a proposal to revert stable page write temporarily because it
causes a huge latency for some applications.

Thanks,
                                                - Zheng

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