linux-kernel - Re: [PATCH] sysctl: Add a feature to drop caches selectively

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Message-ID: <1403860094.3954.6.camel@sauron.fi.intel.com>
Date:	Fri, 27 Jun 2014 12:08:14 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Matthias Schniedermeyer <ms@...d.de>
Cc:	Luká? Czerner <lczerner@...hat.com>,
	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>,
	Dave Chinner <david@...morbit.com>,
	Thomas Knauth <thomas.knauth@....de>,
	David Rientjes <rientjes@...gle.com>,
	Maksym Planeta <mcsim.planeta@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sysctl: Add a feature to drop caches selectively

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

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