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Message-ID: <1403860094.3954.6.camel@sauron.fi.intel.com>
Subject: Re: [PATCH] sysctl: Add a feature to drop caches selectively
From: Artem Bityutskiy <dedekind1@gmail.com>
Reply-To: dedekind1@gmail.com
To: Matthias Schniedermeyer <ms@citd.de>
Cc: =?ISO-8859-1?Q?Luk=E1=3F?= Czerner <lczerner@redhat.com>,
        Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>,
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Date: Fri, 27 Jun 2014 12:08:14 +0300
In-Reply-To: <20140627084139.GA29704@citd.de>
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On Fri, 2014-06-27 at 10:41 +0200, Matthias Schniedermeyer wrote:
> On 26.06.2014 13:57, Luká? Czerner wrote:
> 
> > > So if the authors want to sell this new interface (in whatever form) to
> > > the kernel community, they should start with providing a solid use-case,
> > > with some more details, explore alternatives and show how the
> > > alternatives do not work for them.
> > 
> > Yes please, let's see some solid use-case for this.
> 
> Personally i would want it to verify files after copying them:
> Especially while moving files:
> - Copy a file
> - <drop cache>
> - Verify that it really is correct on stable storage
> - Remove original file

To make 100% sure you'd not only need to drop VFS-level caches but also
file-system-level caches. Indeed, file-systems have their own rather
buffers for different indexing data-structures, etc. The unmount/mount
sequence takes care of that.

-- 
Best Regards,
Artem Bityutskiy


From mboxrd@z Thu Jan  1 00:00:00 1970
From: Artem Bityutskiy <dedekind1@gmail.com>
Subject: Re: [PATCH] sysctl: Add a feature to drop caches selectively
Date: Fri, 27 Jun 2014 12:08:14 +0300
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Cc: =?ISO-8859-1?Q?Luk=E1=3F?= Czerner <lczerner@redhat.com>,
	Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>,
	Dave Chinner <david@fromorbit.com>,
	Thomas Knauth <thomas.knauth@gmx.de>,
	David Rientjes <rientjes@google.com>,
	Maksym Planeta <mcsim.planeta@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
To: Matthias Schniedermeyer <ms@citd.de>
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On Fri, 2014-06-27 at 10:41 +0200, Matthias Schniedermeyer wrote:
> On 26.06.2014 13:57, Luk=C3=A1? Czerner wrote:
>=20
> > > So if the authors want to sell this new interface (in whatever fo=
rm) to
> > > the kernel community, they should start with providing a solid us=
e-case,
> > > with some more details, explore alternatives and show how the
> > > alternatives do not work for them.
> >=20
> > Yes please, let's see some solid use-case for this.
>=20
> Personally i would want it to verify files after copying them:
> Especially while moving files:
> - Copy a file
> - <drop cache>
> - Verify that it really is correct on stable storage
> - Remove original file

To make 100% sure you'd not only need to drop VFS-level caches but also
file-system-level caches. Indeed, file-systems have their own rather
buffers for different indexing data-structures, etc. The unmount/mount
sequence takes care of that.

--=20
Best Regards,
Artem Bityutskiy

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